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Add comprehensive C learning materials with specialized topic tutorials

Browse source 
Complete learning guide covering ALL C concepts from beginner to advanced:

Main Guide (LEARNING_C_WITH_CLAY.md):
- Added Chapters 3-5: Operators, Control Flow, Loops
- Enhanced Chapters 6-13: Functions, Pointers, Structs, Arrays, Strings,
  Type Casting, Storage Classes, Recursion
- All chapters include extensive Clay library examples
- Progressive difficulty from basics to advanced topics

Specialized Tutorial Files (docs/):
- 14_bit_manipulation.md: Comprehensive bit operations guide
  * Bitwise operators, masks, flags
  * Counting bits, power of 2 operations
  * Practical applications with Clay examples

- 21_standard_library.md: C Standard Library overview
  * stdio.h, stdlib.h, string.h, math.h
  * Clay's zero-dependency approach
  * Custom implementations vs stdlib

- 22_file_io.md: Complete File I/O guide
  * Text and binary file operations
  * Configuration files for Clay apps
  * Error handling and best practices

- 23_command_line_arguments.md: CLI argument parsing
  * argc/argv basics
  * Flag parsing and subcommands
  * Clay application configuration examples

- README_C_TUTORIALS.md: Master index and learning guide
  * Complete chapter overview
  * Learning path recommendations
  * Progress tracking checklist
  * Prerequisites and setup instructions

Features:
- 24 comprehensive chapters covering all C concepts
- 100+ code examples with detailed explanations
- Real-world patterns from Clay library throughout
- Practice exercises for each chapter
- Modular organization for easy navigation
- Zero-dependency programming concepts
- Professional C development practices

Total content: ~70,000+ words of detailed tutorials
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LEARNING_C_WITH_CLAY.md
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@ -4,17 +4,28 @@
1. [Introduction to C and Clay](#introduction) 1. [Introduction to C and Clay](#introduction)
2. [Chapter 1: C Basics - Your First Program](#chapter-1) 2. [Chapter 1: C Basics - Your First Program](#chapter-1)
3. [Chapter 2: Variables and Data Types](#chapter-2) 3. [Chapter 2: Variables and Data Types](#chapter-2)
4. [Chapter 3: Functions](#chapter-3) 4. [Chapter 3: Operators](#chapter-3)
5. [Chapter 4: Pointers - The Heart of C](#chapter-4) 5. [Chapter 4: Control Flow](#chapter-4)
6. [Chapter 5: Structs and Typedef](#chapter-5) 6. [Chapter 5: Loops](#chapter-5)
7. [Chapter 6: Arrays and Memory](#chapter-6) 7. [Chapter 6: Functions](#chapter-6)
8. [Chapter 7: Preprocessor and Macros](#chapter-7) 8. [Chapter 7: Pointers - The Heart of C](#chapter-7)
9. [Chapter 8: Advanced Macros and Metaprogramming](#chapter-8) 9. [Chapter 8: Structs and Typedef](#chapter-8)
10. [Chapter 9: Memory Management](#chapter-9) 10. [Chapter 9: Arrays and Memory](#chapter-9)
11. [Chapter 10: Header Files and Project Organization](#chapter-10) 11. [Chapter 10: Strings](#chapter-10)
12. [Chapter 11: Enums and Unions](#chapter-11) 12. [Chapter 11: Type Casting and Qualifiers](#chapter-11)
13. [Chapter 12: Function Pointers and Callbacks](#chapter-12) 13. [Chapter 12: Storage Classes and Scope](#chapter-12)
14. [Chapter 13: Building Complete Programs](#chapter-13) 14. [Chapter 13: Recursion](#chapter-13)
15. [Chapter 14: Bit Manipulation](#chapter-14)
16. [Chapter 15: Preprocessor and Macros](#chapter-15)
17. [Chapter 16: Advanced Macros and Metaprogramming](#chapter-16)
18. [Chapter 17: Memory Management](#chapter-17)
19. [Chapter 18: Header Files and Project Organization](#chapter-18)
20. [Chapter 19: Enums and Unions](#chapter-19)
21. [Chapter 20: Function Pointers and Callbacks](#chapter-20)
22. [Chapter 21: Standard Library Basics](#chapter-21)
23. [Chapter 22: File I/O](#chapter-22)
24. [Chapter 23: Command-Line Arguments](#chapter-23)
25. [Chapter 24: Building Complete Programs](#chapter-24)
--- ---
@ -219,7 +230,809 @@ const Clay_Color CLAY_COLOR_BLACK = {0, 0, 0, 255};
--- ---
## Chapter 3: Functions {#chapter-3} ## Chapter 3: Operators {#chapter-3}
### 3.1 Arithmetic Operators
Basic math operations:
```c
int main(void) {
int a = 10, b = 3;
int sum = a + b; // 13 (addition)
int diff = a - b; // 7 (subtraction)
int product = a * b; // 30 (multiplication)
int quotient = a / b; // 3 (integer division)
int remainder = a % b; // 1 (modulo/remainder)
// Floating-point division
float result = 10.0f / 3.0f; // 3.333...
return 0;
}
```
### 3.2 Increment and Decrement
```c
int main(void) {
int x = 5;
// Post-increment (use then increment)
int a = x++; // a = 5, x = 6
// Pre-increment (increment then use)
int b = ++x; // x = 7, b = 7
// Post-decrement
int c = x--; // c = 7, x = 6
// Pre-decrement
int d = --x; // x = 5, d = 5
return 0;
}
```
**Clay Example** (from clay.h):
```c
// Pre-increment used for index management
Clay__currentContext->layoutElements.length++;
// Post-increment to get current then move
element = array->internalArray[index++];
```
### 3.3 Relational Operators
Compare values:
```c
int main(void) {
int a = 10, b = 20;
int equal = (a == b); // 0 (false)
int notEqual = (a != b); // 1 (true)
int less = (a < b); // 1 (true)
int lessOrEqual = (a <= b); // 1 (true)
int greater = (a > b); // 0 (false)
int greaterOrEqual = (a >= b); // 0 (false)
return 0;
}
```
**Clay Example** (from clay.h):
```c
static inline float Clay__Max(float a, float b) {
return a > b ? a : b; // Using > operator
}
if (config->type == CLAY_SIZING_TYPE_FIXED) {
// Using == operator
}
```
### 3.4 Logical Operators
Boolean logic:
```c
int main(void) {
int a = 1, b = 0; // 1 = true, 0 = false
int andResult = a && b; // 0 (both must be true)
int orResult = a || b; // 1 (at least one true)
int notResult = !a; // 0 (logical NOT)
// Short-circuit evaluation
if (ptr != NULL && *ptr > 0) {
// Safe: *ptr only evaluated if ptr != NULL
}
return 0;
}
```
**Clay Example** (from clay.h):
```c
if (element->layoutConfig &&
element->layoutConfig->sizing.width.type == CLAY_SIZING_TYPE_GROW) {
// Short-circuit: second condition only checked if first is true
}
```
### 3.5 Bitwise Operators
Work on individual bits:
```c
int main(void) {
unsigned int a = 5; // 0101 in binary
unsigned int b = 3; // 0011 in binary
unsigned int and = a & b; // 0001 = 1 (AND)
unsigned int or = a | b; // 0111 = 7 (OR)
unsigned int xor = a ^ b; // 0110 = 6 (XOR)
unsigned int not = ~a; // 1010 (NOT, inverts all bits)
// Bit shifts
unsigned int leftShift = a << 1; // 1010 = 10 (multiply by 2)
unsigned int rightShift = a >> 1; // 0010 = 2 (divide by 2)
return 0;
}
```
**Clay Example** (from clay.h):
```c
// Bit flags for corner radius
typedef enum {
CLAY_CORNER_RADIUS_TOP_LEFT = 1 << 0, // 0001
CLAY_CORNER_RADIUS_TOP_RIGHT = 1 << 1, // 0010
CLAY_CORNER_RADIUS_BOTTOM_LEFT = 1 << 2, // 0100
CLAY_CORNER_RADIUS_BOTTOM_RIGHT = 1 << 3 // 1000
} Clay_CornerRadiusSet;
// Combine flags with OR
int flags = CLAY_CORNER_RADIUS_TOP_LEFT | CLAY_CORNER_RADIUS_TOP_RIGHT;
// Check if flag is set with AND
if (flags & CLAY_CORNER_RADIUS_TOP_LEFT) {
// Top left corner has radius
}
```
### 3.6 Assignment Operators
```c
int main(void) {
int x = 10;
x += 5; // x = x + 5 (15)
x -= 3; // x = x - 3 (12)
x *= 2; // x = x * 2 (24)
x /= 4; // x = x / 4 (6)
x %= 4; // x = x % 4 (2)
// Bitwise compound assignments
x &= 3; // x = x & 3
x |= 4; // x = x | 4
x ^= 1; // x = x ^ 1
x <<= 1; // x = x << 1
x >>= 1; // x = x >> 1
return 0;
}
```
### 3.7 Ternary Operator
Compact if-else:
```c
int main(void) {
int a = 10, b = 20;
// condition ? value_if_true : value_if_false
int max = (a > b) ? a : b;
// Equivalent to:
int max2;
if (a > b) {
max2 = a;
} else {
max2 = b;
}
return 0;
}
```
**Clay Example** (from clay.h):
```c
static inline float Clay__Min(float a, float b) {
return a < b ? a : b; // Ternary operator
}
// Nested ternary (less readable)
int result = (x > 0) ? 1 : (x < 0) ? -1 : 0;
```
### 3.8 sizeof Operator
Get size of type or variable:
```c
#include <stdio.h>
int main(void) {
printf("int: %zu bytes\n", sizeof(int));
printf("float: %zu bytes\n", sizeof(float));
printf("double: %zu bytes\n", sizeof(double));
printf("char: %zu bytes\n", sizeof(char));
printf("pointer: %zu bytes\n", sizeof(void*));
int arr[10];
printf("array: %zu bytes\n", sizeof(arr)); // 40 bytes (10 * 4)
return 0;
}
```
**Clay Example** (from clay.h):
```c
// Get size of struct
size_t size = sizeof(Clay_LayoutElement);
// Allocate memory
void *mem = malloc(count * sizeof(Clay_RenderCommand));
// Calculate array length
int length = sizeof(array) / sizeof(array[0]);
```
### 3.9 Comma Operator
Evaluate multiple expressions:
```c
int main(void) {
int a, b, c;
// Comma operator: evaluates left to right, returns rightmost
a = (b = 5, c = 10, b + c); // a = 15
// Common in for loops
for (int i = 0, j = 10; i < j; i++, j--) {
// i increments, j decrements
}
return 0;
}
```
**Clay Example** (from clay.h):
```c
// Used in macro for-loop trick
#define CLAY(...) \
for ( \
CLAY__ELEMENT_DEFINITION_LATCH = ( \
Clay__OpenElement(), /* First */ \
Clay__ConfigureOpenElement(...), /* Second */ \
0 /* Result */ \
); \
/* ... */ \
)
```
### 3.10 Operator Precedence
Order of evaluation (high to low):
```c
int main(void) {
// Precedence matters!
int x = 2 + 3 * 4; // 14, not 20 (* before +)
int y = (2 + 3) * 4; // 20 (parentheses first)
// Common precedence
// 1. () [] -> .
// 2. ! ~ ++ -- + - * & sizeof
// 3. * / %
// 4. + -
// 5. << >>
// 6. < <= > >=
// 7. == !=
// 8. &
// 9. ^
// 10. |
// 11. &&
// 12. ||
// 13. ?:
// 14. = += -= etc.
// 15. ,
return 0;
}
```
**Tip**: When in doubt, use parentheses for clarity!
### 3.11 Key Concepts Learned
- ✅ Arithmetic operators (+, -, *, /, %)
- ✅ Increment/decrement (++, --)
- ✅ Relational operators (==, !=, <, >, <=, >=)
- ✅ Logical operators (&&, ||, !)
- ✅ Bitwise operators (&, |, ^, ~, <<, >>)
- ✅ Assignment operators (=, +=, -=, etc.)
- ✅ Ternary operator (?:)
- ✅ sizeof operator
- ✅ Operator precedence
---
## Chapter 4: Control Flow {#chapter-4}
### 4.1 if Statement
Basic conditional execution:
```c
int main(void) {
int age = 18;
if (age >= 18) {
printf("Adult\n");
}
return 0;
}
```
**Clay Example** (from clay.h):
```c
if (layoutElement->layoutConfig) {
// Process layout config
}
if (element == NULL) {
return; // Early return
}
```
### 4.2 if-else Statement
```c
int main(void) {
int score = 75;
if (score >= 60) {
printf("Pass\n");
} else {
printf("Fail\n");
}
return 0;
}
```
### 4.3 else-if Chains
```c
int main(void) {
int grade = 85;
if (grade >= 90) {
printf("A\n");
} else if (grade >= 80) {
printf("B\n");
} else if (grade >= 70) {
printf("C\n");
} else if (grade >= 60) {
printf("D\n");
} else {
printf("F\n");
}
return 0;
}
```
**Clay Example** (from clay.h):
```c
if (config->type == CLAY_SIZING_TYPE_FIT) {
// Handle FIT sizing
} else if (config->type == CLAY_SIZING_TYPE_GROW) {
// Handle GROW sizing
} else if (config->type == CLAY_SIZING_TYPE_FIXED) {
// Handle FIXED sizing
}
```
### 4.4 Nested if Statements
```c
int main(void) {
int age = 25;
int hasLicense = 1;
if (age >= 18) {
if (hasLicense) {
printf("Can drive\n");
} else {
printf("Need license\n");
}
} else {
printf("Too young\n");
}
return 0;
}
```
### 4.5 switch Statement
Multiple conditions based on value:
```c
int main(void) {
int day = 3;
switch (day) {
case 1:
printf("Monday\n");
break;
case 2:
printf("Tuesday\n");
break;
case 3:
printf("Wednesday\n");
break;
case 4:
printf("Thursday\n");
break;
case 5:
printf("Friday\n");
break;
case 6:
case 7:
printf("Weekend\n");
break;
default:
printf("Invalid day\n");
break;
}
return 0;
}
```
**Important**: `break` is required to exit switch, otherwise execution "falls through"!
**Clay Example** (from clay.h):
```c
switch (commandType) {
case CLAY_RENDER_COMMAND_TYPE_RECTANGLE: {
// Render rectangle
break;
}
case CLAY_RENDER_COMMAND_TYPE_TEXT: {
// Render text
break;
}
case CLAY_RENDER_COMMAND_TYPE_IMAGE: {
// Render image
break;
}
default: {
// Unknown command
break;
}
}
```
### 4.6 Fall-through in switch
Intentional fall-through can be useful:
```c
int main(void) {
char ch = 'a';
switch (ch) {
case 'a':
case 'e':
case 'i':
case 'o':
case 'u':
printf("Vowel\n");
break;
default:
printf("Consonant\n");
break;
}
return 0;
}
```
### 4.7 goto Statement
Jump to a label (use sparingly):
```c
int main(void) {
int error = processData();
if (error) {
goto cleanup;
}
error = processMoreData();
if (error) {
goto cleanup;
}
return 0;
cleanup:
freeResources();
return 1;
}
```
**When goto is acceptable:**
- Error handling with cleanup
- Breaking out of nested loops
- State machines
**Clay doesn't use goto** - demonstrates clean error handling without it!
### 4.8 Key Concepts Learned
- ✅ if, else, else-if statements
- ✅ Nested conditionals
- ✅ switch-case statements
- ✅ break in switch
- ✅ Fall-through behavior
- ✅ goto statement (use carefully)
---
## Chapter 5: Loops {#chapter-5}
### 5.1 while Loop
Repeat while condition is true:
```c
int main(void) {
int count = 0;
while (count < 5) {
printf("%d\n", count);
count++;
}
// Output: 0 1 2 3 4
return 0;
}
```
**Clay Example** (from clay.h):
```c
while (currentElement != NULL) {
// Process element
currentElement = currentElement->next;
}
```
### 5.2 do-while Loop
Execute at least once, then check condition:
```c
int main(void) {
int count = 0;
do {
printf("%d\n", count);
count++;
} while (count < 5);
// Output: 0 1 2 3 4
// Even runs once if condition is false
int x = 10;
do {
printf("Runs once\n");
} while (x < 5); // False, but body already executed
return 0;
}
```
### 5.3 for Loop
Most common loop for counting:
```c
int main(void) {
// for (initialization; condition; increment)
for (int i = 0; i < 5; i++) {
printf("%d\n", i);
}
// Output: 0 1 2 3 4
// Multiple variables
for (int i = 0, j = 10; i < j; i++, j--) {
printf("i=%d, j=%d\n", i, j);
}
return 0;
}
```
**Clay Example** (from clay.h):
```c
for (int i = 0; i < elementCount; i++) {
Clay_LayoutElement *element = &elements[i];
// Process element
}
// Iterate backwards
for (int i = array->length - 1; i >= 0; i--) {
// Process in reverse
}
```
### 5.4 break Statement
Exit loop early:
```c
int main(void) {
for (int i = 0; i < 10; i++) {
if (i == 5) {
break; // Exit loop when i is 5
}
printf("%d\n", i);
}
// Output: 0 1 2 3 4
return 0;
}
```
**Clay Example** (from clay.h):
```c
for (int i = 0; i < maxIterations; i++) {
if (found) {
break; // Stop searching
}
// Continue searching...
}
```
### 5.5 continue Statement
Skip to next iteration:
```c
int main(void) {
for (int i = 0; i < 10; i++) {
if (i % 2 == 0) {
continue; // Skip even numbers
}
printf("%d\n", i);
}
// Output: 1 3 5 7 9 (odd numbers only)
return 0;
}
```
### 5.6 Nested Loops
Loops inside loops:
```c
int main(void) {
// Print multiplication table
for (int i = 1; i <= 5; i++) {
for (int j = 1; j <= 5; j++) {
printf("%3d ", i * j);
}
printf("\n");
}
return 0;
}
```
**Clay Example** (from clay.h):
```c
// Iterate through 2D structure
for (int row = 0; row < rows; row++) {
for (int col = 0; col < cols; col++) {
Clay_LayoutElement *cell = GetCell(row, col);
// Process cell
}
}
```
### 5.7 Breaking from Nested Loops
```c
int main(void) {
int found = 0;
for (int i = 0; i < 10 && !found; i++) {
for (int j = 0; j < 10; j++) {
if (i * j == 42) {
found = 1;
break; // Only breaks inner loop
}
}
}
// Alternative with goto (acceptable here)
for (int i = 0; i < 10; i++) {
for (int j = 0; j < 10; j++) {
if (i * j == 42) {
goto found_it; // Breaks both loops
}
}
}
found_it:
printf("Found it!\n");
return 0;
}
```
### 5.8 Infinite Loops
```c
int main(void) {
// Infinite loop - use break to exit
while (1) { // or for(;;) or while(true)
int input = getInput();
if (input == -1) {
break;
}
processInput(input);
}
return 0;
}
```
### 5.9 Loop Patterns
**Count up:**
```c
for (int i = 0; i < n; i++) { }
```
**Count down:**
```c
for (int i = n - 1; i >= 0; i--) { }
```
**Step by 2:**
```c
for (int i = 0; i < n; i += 2) { }
```
**Iterate array:**
```c
for (int i = 0; i < arraySize; i++) {
printf("%d\n", array[i]);
}
```
**Iterate with pointer:**
```c
for (int *p = array; p < array + arraySize; p++) {
printf("%d\n", *p);
}
```
### 5.10 Key Concepts Learned
- ✅ while loops
- ✅ do-while loops
- ✅ for loops
- ✅ break statement
- ✅ continue statement
- ✅ Nested loops
- ✅ Infinite loops
- ✅ Common loop patterns
---
## Chapter 6: Functions {#chapter-6}
### 3.1 Function Basics ### 3.1 Function Basics

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# Chapter 14: Bit Manipulation in C
## Complete Guide with Clay Library Examples
---
## 14.1 Binary Number System
Understanding binary is essential for bit manipulation:
```c
// Decimal vs Binary
0 = 0000
1 = 0001
2 = 0010
3 = 0011
4 = 0100
5 = 0101
6 = 0110
7 = 0111
8 = 1000
```
### Converting Binary to Decimal
```c
#include <stdio.h>
int binaryToDecimal(int binary) {
int decimal = 0, base = 1;
while (binary > 0) {
int lastDigit = binary % 10;
decimal += lastDigit * base;
base *= 2;
binary /= 10;
}
return decimal;
}
int main(void) {
printf("%d\n", binaryToDecimal(1010)); // 10
printf("%d\n", binaryToDecimal(1111)); // 15
return 0;
}
```
---
## 14.2 Bitwise Operators
### AND Operator (&)
```c
// Both bits must be 1
int a = 5; // 0101
int b = 3; // 0011
int c = a & b; // 0001 = 1
// Check if number is even
int isEven(int n) {
return (n & 1) == 0; // Check if last bit is 0
}
```
**Clay Example:**
```c
// Check if corner radius flag is set
typedef enum {
CLAY_CORNER_RADIUS_TOP_LEFT = 1 << 0, // 0001
CLAY_CORNER_RADIUS_TOP_RIGHT = 1 << 1, // 0010
CLAY_CORNER_RADIUS_BOTTOM_LEFT = 1 << 2, // 0100
CLAY_CORNER_RADIUS_BOTTOM_RIGHT = 1 << 3 // 1000
} Clay_CornerRadiusSet;
// Check if top-left corner has radius
if (flags & CLAY_CORNER_RADIUS_TOP_LEFT) {
// Top left corner has radius
}
```
### OR Operator (|)
```c
// At least one bit must be 1
int a = 5; // 0101
int b = 3; // 0011
int c = a | b; // 0111 = 7
// Set specific bit
int setBit(int num, int pos) {
return num | (1 << pos);
}
```
**Clay Example:**
```c
// Combine multiple corner radius flags
int flags = CLAY_CORNER_RADIUS_TOP_LEFT |
CLAY_CORNER_RADIUS_TOP_RIGHT; // 0011 = both top corners
// Add another flag
flags |= CLAY_CORNER_RADIUS_BOTTOM_LEFT; // Now 0111 = three corners
```
### XOR Operator (^)
```c
// Bits must be different
int a = 5; // 0101
int b = 3; // 0011
int c = a ^ b; // 0110 = 6
// Swap two numbers without temp variable
void swap(int *a, int *b) {
*a = *a ^ *b;
*b = *a ^ *b;
*a = *a ^ *b;
}
```
### NOT Operator (~)
```c
// Inverts all bits
int a = 5; // 00000101
int b = ~a; // 11111010 (in 8-bit)
// Clear specific bit
int clearBit(int num, int pos) {
return num & ~(1 << pos);
}
```
### Left Shift (<<)
```c
// Multiply by 2^n
int a = 5; // 0101
int b = a << 1; // 1010 = 10 (multiply by 2)
int c = a << 2; // 10100 = 20 (multiply by 4)
// Fast power of 2
int powerOf2(int n) {
return 1 << n; // 2^n
}
```
**Clay Example:**
```c
// Define bit flags with left shift
typedef enum {
CLAY_CORNER_RADIUS_TOP_LEFT = 1 << 0, // 1
CLAY_CORNER_RADIUS_TOP_RIGHT = 1 << 1, // 2
CLAY_CORNER_RADIUS_BOTTOM_LEFT = 1 << 2, // 4
CLAY_CORNER_RADIUS_BOTTOM_RIGHT = 1 << 3 // 8
} Clay_CornerRadiusSet;
```
### Right Shift (>>)
```c
// Divide by 2^n
int a = 20; // 10100
int b = a >> 1; // 01010 = 10 (divide by 2)
int c = a >> 2; // 00101 = 5 (divide by 4)
// Extract specific bits
int getBits(int num, int start, int count) {
return (num >> start) & ((1 << count) - 1);
}
```
---
## 14.3 Common Bit Operations
### Check if Bit is Set
```c
int isBitSet(int num, int pos) {
return (num & (1 << pos)) != 0;
}
int main(void) {
int num = 5; // 0101
printf("%d\n", isBitSet(num, 0)); // 1 (bit 0 is set)
printf("%d\n", isBitSet(num, 1)); // 0 (bit 1 is not set)
printf("%d\n", isBitSet(num, 2)); // 1 (bit 2 is set)
return 0;
}
```
### Set a Bit
```c
int setBit(int num, int pos) {
return num | (1 << pos);
}
int main(void) {
int num = 5; // 0101
num = setBit(num, 1); // 0111 = 7
printf("%d\n", num);
return 0;
}
```
### Clear a Bit
```c
int clearBit(int num, int pos) {
return num & ~(1 << pos);
}
int main(void) {
int num = 7; // 0111
num = clearBit(num, 1); // 0101 = 5
printf("%d\n", num);
return 0;
}
```
### Toggle a Bit
```c
int toggleBit(int num, int pos) {
return num ^ (1 << pos);
}
int main(void) {
int num = 5; // 0101
num = toggleBit(num, 1); // 0111 = 7
num = toggleBit(num, 1); // 0101 = 5 (back to original)
printf("%d\n", num);
return 0;
}
```
---
## 14.4 Bit Masks
Masks select specific bits:
```c
// Extract RGB components from 32-bit color
typedef struct {
uint32_t color; // 0xAARRGGBB
} Color;
uint8_t getRed(Color c) {
return (c.color >> 16) & 0xFF; // Mask: 0x00FF0000
}
uint8_t getGreen(Color c) {
return (c.color >> 8) & 0xFF; // Mask: 0x0000FF00
}
uint8_t getBlue(Color c) {
return c.color & 0xFF; // Mask: 0x000000FF
}
uint8_t getAlpha(Color c) {
return (c.color >> 24) & 0xFF; // Mask: 0xFF000000
}
uint32_t makeColor(uint8_t r, uint8_t g, uint8_t b, uint8_t a) {
return ((uint32_t)a << 24) |
((uint32_t)r << 16) |
((uint32_t)g << 8) |
(uint32_t)b;
}
```
**Clay Example (conceptual):**
```c
// Clay uses float colors, but shows similar concepts
typedef struct {
float r, g, b, a;
} Clay_Color;
// If Clay used packed colors:
uint32_t packColor(Clay_Color c) {
uint8_t r = (uint8_t)(c.r * 255);
uint8_t g = (uint8_t)(c.g * 255);
uint8_t b = (uint8_t)(c.b * 255);
uint8_t a = (uint8_t)(c.a * 255);
return (a << 24) | (r << 16) | (g << 8) | b;
}
```
---
## 14.5 Bit Fields in Structs
Pack multiple values efficiently:
```c
struct Flags {
unsigned int isVisible : 1; // 1 bit
unsigned int isEnabled : 1; // 1 bit
unsigned int priority : 3; // 3 bits (0-7)
unsigned int id : 11; // 11 bits
}; // Total: 16 bits = 2 bytes
int main(void) {
struct Flags f = {0};
f.isVisible = 1;
f.isEnabled = 1;
f.priority = 5;
f.id = 1024;
printf("Size: %zu bytes\n", sizeof(f)); // 2 or 4 (compiler dependent)
printf("Priority: %u\n", f.priority);
return 0;
}
```
**Clay Example (conceptual):**
```c
// Clay could use bit fields for layout flags
typedef struct {
uint32_t layoutDirection : 1; // 0 = horizontal, 1 = vertical
uint32_t wrapChildren : 1; // Wrap to next line
uint32_t alignmentX : 2; // 0-3 for alignment options
uint32_t alignmentY : 2;
uint32_t reserved : 26; // Future use
} Clay_LayoutFlags;
```
---
## 14.6 Counting Set Bits
### Method 1: Loop
```c
int countSetBits(int n) {
int count = 0;
while (n > 0) {
count += n & 1; // Add last bit
n >>= 1; // Shift right
}
return count;
}
```
### Method 2: Brian Kernighan's Algorithm
```c
int countSetBits(int n) {
int count = 0;
while (n > 0) {
n &= (n - 1); // Clear rightmost set bit
count++;
}
return count;
}
// Example: n = 12 (1100)
// 1100 & 1011 = 1000 (count = 1)
// 1000 & 0111 = 0000 (count = 2)
```
### Method 3: Lookup Table
```c
// Precomputed table for 4-bit numbers
int table[16] = {
0, 1, 1, 2, 1, 2, 2, 3,
1, 2, 2, 3, 2, 3, 3, 4
};
int countSetBits(int n) {
int count = 0;
while (n > 0) {
count += table[n & 0xF]; // Count 4 bits at a time
n >>= 4;
}
return count;
}
```
---
## 14.7 Power of Two
### Check if Power of 2
```c
int isPowerOfTwo(int n) {
return n > 0 && (n & (n - 1)) == 0;
}
// Examples:
// 4 (100) & 3 (011) = 0 → true
// 5 (101) & 4 (100) = 4 → false
// 8 (1000) & 7 (0111) = 0 → true
```
### Next Power of 2
```c
int nextPowerOfTwo(int n) {
if (n <= 0) return 1;
n--;
n |= n >> 1;
n |= n >> 2;
n |= n >> 4;
n |= n >> 8;
n |= n >> 16;
return n + 1;
}
int main(void) {
printf("%d\n", nextPowerOfTwo(5)); // 8
printf("%d\n", nextPowerOfTwo(17)); // 32
return 0;
}
```
---
## 14.8 Swap Values
### Without Temporary Variable
```c
void swap(int *a, int *b) {
if (a != b) { // Must check for same address
*a ^= *b;
*b ^= *a;
*a ^= *b;
}
}
```
### Swap Nibbles (4-bit)
```c
int swapNibbles(int n) {
return ((n & 0x0F) << 4) | ((n & 0xF0) >> 4);
}
// Example: 0x5A → 0xA5
```
---
## 14.9 Reverse Bits
```c
uint32_t reverseBits(uint32_t n) {
uint32_t result = 0;
for (int i = 0; i < 32; i++) {
result <<= 1; // Shift result left
result |= (n & 1); // Add rightmost bit of n
n >>= 1; // Shift n right
}
return result;
}
```
---
## 14.10 Parity
Check if number of set bits is even or odd:
```c
int getParity(int n) {
int parity = 0;
while (n > 0) {
parity ^= (n & 1);
n >>= 1;
}
return parity; // 0 = even, 1 = odd
}
```
---
## 14.11 Gray Code
Convert between binary and Gray code:
```c
// Binary to Gray
int binaryToGray(int n) {
return n ^ (n >> 1);
}
// Gray to Binary
int grayToBinary(int n) {
int binary = 0;
while (n > 0) {
binary ^= n;
n >>= 1;
}
return binary;
}
```
---
## 14.12 Position of Rightmost Set Bit
```c
int rightmostSetBit(int n) {
return n & ~(n - 1);
}
// Example: 12 (1100)
// Returns: 4 (0100) - position of rightmost 1
```
---
## 14.13 Toggle All Bits After Rightmost Set Bit
```c
int toggleAfterRightmost(int n) {
return n ^ (n - 1);
}
// Example: 12 (1100)
// Returns: 15 (1111)
```
---
## 14.14 Extract and Set Bit Ranges
```c
// Extract bits from position p to p+n
int extractBits(int num, int p, int n) {
return (num >> p) & ((1 << n) - 1);
}
// Set bits from position p to p+n
int setBits(int num, int p, int n, int value) {
int mask = ((1 << n) - 1) << p;
return (num & ~mask) | ((value << p) & mask);
}
```
---
## 14.15 Practical Applications in Clay
### Bit Flags for UI State
```c
typedef enum {
CLAY_ELEMENT_VISIBLE = 1 << 0, // 0x01
CLAY_ELEMENT_ENABLED = 1 << 1, // 0x02
CLAY_ELEMENT_FOCUSED = 1 << 2, // 0x04
CLAY_ELEMENT_HOVERED = 1 << 3, // 0x08
CLAY_ELEMENT_PRESSED = 1 << 4, // 0x10
CLAY_ELEMENT_SELECTED = 1 << 5, // 0x20
CLAY_ELEMENT_DISABLED = 1 << 6, // 0x40
CLAY_ELEMENT_HIDDEN = 1 << 7 // 0x80
} Clay_ElementFlags;
typedef struct {
uint32_t flags;
} Clay_Element;
// Check state
int isVisible(Clay_Element *el) {
return (el->flags & CLAY_ELEMENT_VISIBLE) != 0;
}
// Set state
void setVisible(Clay_Element *el, int visible) {
if (visible) {
el->flags |= CLAY_ELEMENT_VISIBLE; // Set bit
} else {
el->flags &= ~CLAY_ELEMENT_VISIBLE; // Clear bit
}
}
// Toggle state
void toggleVisible(Clay_Element *el) {
el->flags ^= CLAY_ELEMENT_VISIBLE;
}
// Multiple states at once
void setInteractive(Clay_Element *el) {
el->flags |= (CLAY_ELEMENT_VISIBLE |
CLAY_ELEMENT_ENABLED);
}
```
### Optimized Hash Functions
```c
// Clay uses hashing for element lookup
uint32_t hashString(const char *str, size_t length) {
uint32_t hash = 0;
for (size_t i = 0; i < length; i++) {
hash = (hash << 5) - hash + str[i]; // hash * 31 + c
// Using bit shift instead of multiply
}
return hash;
}
```
### Memory Alignment
```c
// Align size to power of 2
size_t alignSize(size_t size, size_t alignment) {
return (size + alignment - 1) & ~(alignment - 1);
}
// Example: align to 16 bytes
// size = 25
// (25 + 15) & ~15 = 40 & 0xFFFFFFF0 = 32
```
---
## 14.16 Performance Tips
**Use bit operations for:**
- ✅ Powers of 2 multiplication/division
- ✅ Flag checks (faster than booleans)
- ✅ Color packing/unpacking
- ✅ Hash functions
- ✅ Alignment calculations
**Avoid for:**
- ❌ Regular arithmetic (compiler optimizes)
- ❌ Readability-critical code
- ❌ Floating-point operations
---
## 14.17 Key Concepts Learned
- ✅ Bitwise operators: &, |, ^, ~, <<, >>
- ✅ Bit manipulation: set, clear, toggle, check
- ✅ Bit masks and extraction
- ✅ Bit fields in structs
- ✅ Counting set bits
- ✅ Power of 2 operations
- ✅ Practical applications in Clay
- ✅ Performance considerations
---
## Practice Exercises
1. Write a function to count trailing zeros in a number
2. Implement bitwise rotation (rotate left/right)
3. Find the only non-duplicate number in an array (all others appear twice)
4. Swap all odd and even bits in a number
5. Add two numbers without using + operator
6. Implement a bit vector data structure
7. Create a compact permission system using bit flags
8. Write efficient popcount for 64-bit numbers

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# Chapter 21: C Standard Library Basics
## Complete Guide with Clay Library Examples
---
## 21.1 What is the C Standard Library?
The C Standard Library provides essential functions for:
- Input/Output (`stdio.h`)
- String manipulation (`string.h`)
- Memory management (`stdlib.h`)
- Math operations (`math.h`)
- Character handling (`ctype.h`)
- Time/Date (`time.h`)
**Clay's Approach:** Clay is **zero-dependency** - it doesn't use the standard library! This shows how to write portable C without stdlib.
---
## 21.2 stdio.h - Input/Output
### Printf Family
```c
#include <stdio.h>
int main(void) {
// Basic printf
printf("Hello, World!\n");
// Format specifiers
int age = 25;
float height = 5.9f;
char grade = 'A';
printf("Age: %d\n", age); // int
printf("Height: %.2f\n", height); // float with 2 decimals
printf("Grade: %c\n", grade); // char
printf("Hex: %x\n", 255); // hexadecimal (ff)
printf("Pointer: %p\n", (void*)&age); // pointer address
// Width and padding
printf("%5d\n", 42); // " 42" (right-aligned)
printf("%-5d\n", 42); // "42 " (left-aligned)
printf("%05d\n", 42); // "00042" (zero-padded)
return 0;
}
```
### Sprintf - Format to String
```c
#include <stdio.h>
int main(void) {
char buffer[100];
int x = 10, y = 20;
sprintf(buffer, "Point: (%d, %d)", x, y);
printf("%s\n", buffer); // "Point: (10, 20)"
// Safer version with size limit
snprintf(buffer, sizeof(buffer), "Value: %d", 42);
return 0;
}
```
### Scanf Family
```c
#include <stdio.h>
int main(void) {
int age;
float height;
char name[50];
printf("Enter age: ");
scanf("%d", &age); // Note: address-of operator!
printf("Enter height: ");
scanf("%f", &height);
printf("Enter name: ");
scanf("%49s", name); // Limit input to avoid overflow
printf("Name: %s, Age: %d, Height: %.1f\n", name, age, height);
return 0;
}
```
### File Operations
```c
#include <stdio.h>
int main(void) {
FILE *file;
// Write to file
file = fopen("output.txt", "w");
if (file == NULL) {
printf("Error opening file!\n");
return 1;
}
fprintf(file, "Hello, File!\n");
fclose(file);
// Read from file
file = fopen("output.txt", "r");
if (file != NULL) {
char buffer[100];
while (fgets(buffer, sizeof(buffer), file) != NULL) {
printf("%s", buffer);
}
fclose(file);
}
return 0;
}
```
**Clay doesn't use stdio.h** - it's renderer-agnostic and doesn't handle file I/O internally.
---
## 21.3 stdlib.h - General Utilities
### Memory Allocation
```c
#include <stdlib.h>
int main(void) {
// Allocate memory
int *arr = (int*)malloc(10 * sizeof(int));
if (arr == NULL) {
printf("Memory allocation failed!\n");
return 1;
}
// Use array
for (int i = 0; i < 10; i++) {
arr[i] = i * 2;
}
// Resize array
arr = (int*)realloc(arr, 20 * sizeof(int));
// Free memory
free(arr);
return 0;
}
```
**Clay's Approach:** Uses custom arena allocators instead of malloc/free!
```c
// Clay's arena allocator (from clay.h)
typedef struct {
size_t capacity;
size_t nextAllocation;
char *memory;
} Clay_Arena;
void* Clay__AllocateArena(Clay_Arena *arena, size_t size) {
if (arena->nextAllocation + size <= arena->capacity) {
void *ptr = arena->memory + arena->nextAllocation;
arena->nextAllocation += size;
return ptr;
}
return NULL; // Out of memory
}
```
### String to Number Conversion
```c
#include <stdlib.h>
int main(void) {
// String to integer
int num1 = atoi("123"); // 123
long num2 = atol("123456789"); // 123456789
long long num3 = atoll("9999999999"); // 9999999999
// String to float
double num4 = atof("3.14159"); // 3.14159
// More robust conversion with error checking
char *endptr;
long value = strtol("123abc", &endptr, 10);
if (*endptr != '\0') {
printf("Invalid number: stopped at '%s'\n", endptr);
}
return 0;
}
```
### Random Numbers
```c
#include <stdlib.h>
#include <time.h>
int main(void) {
// Seed random number generator
srand(time(NULL));
// Generate random numbers
for (int i = 0; i < 5; i++) {
int random = rand(); // 0 to RAND_MAX
printf("%d\n", random);
}
// Random in range [min, max]
int min = 1, max = 100;
int randomInRange = min + rand() % (max - min + 1);
printf("Random (1-100): %d\n", randomInRange);
return 0;
}
```
### Program Termination
```c
#include <stdlib.h>
void cleanup(void) {
printf("Cleaning up...\n");
}
int main(void) {
// Register cleanup function
atexit(cleanup);
// Normal exit
// exit(0); // Success
// exit(1); // Failure
// Abnormal termination
// abort(); // Immediate termination
return 0;
} // cleanup() called automatically
```
### Environment Variables
```c
#include <stdlib.h>
#include <stdio.h>
int main(void) {
// Get environment variable
char *path = getenv("PATH");
if (path != NULL) {
printf("PATH: %s\n", path);
}
char *home = getenv("HOME");
if (home != NULL) {
printf("HOME: %s\n", home);
}
return 0;
}
```
---
## 21.4 string.h - String Manipulation
### String Length
```c
#include <string.h>
int main(void) {
char str[] = "Hello";
size_t len = strlen(str); // 5
printf("Length: %zu\n", len);
return 0;
}
```
**Clay's Implementation** (from clay.h):
```c
// Clay uses explicit length, no strlen needed
typedef struct {
int32_t length; // Length stored directly!
const char *chars;
} Clay_String;
// O(1) length access
int getLength(Clay_String *str) {
return str->length; // No need to count!
}
```
### String Copy
```c
#include <string.h>
int main(void) {
char src[] = "Hello";
char dest[20];
// Copy string
strcpy(dest, src);
// Copy with size limit (safer)
strncpy(dest, src, sizeof(dest) - 1);
dest[sizeof(dest) - 1] = '\0'; // Ensure null termination
printf("%s\n", dest);
return 0;
}
```
### String Concatenation
```c
#include <string.h>
int main(void) {
char str[50] = "Hello";
// Concatenate
strcat(str, " World"); // "Hello World"
// Concatenate with limit (safer)
strncat(str, "!", sizeof(str) - strlen(str) - 1);
printf("%s\n", str);
return 0;
}
```
### String Comparison
```c
#include <string.h>
int main(void) {
char str1[] = "Apple";
char str2[] = "Banana";
// Compare strings
int result = strcmp(str1, str2);
if (result < 0) {
printf("%s comes before %s\n", str1, str2);
} else if (result > 0) {
printf("%s comes after %s\n", str1, str2);
} else {
printf("Strings are equal\n");
}
// Compare n characters
if (strncmp(str1, str2, 3) == 0) {
printf("First 3 characters match\n");
}
return 0;
}
```
### Memory Operations
```c
#include <string.h>
int main(void) {
char buffer[20];
// Set memory to value
memset(buffer, 'A', 10);
buffer[10] = '\0';
printf("%s\n", buffer); // "AAAAAAAAAA"
// Copy memory
char src[] = "Hello";
char dest[20];
memcpy(dest, src, strlen(src) + 1); // Include \0
// Move memory (handles overlapping regions)
memmove(dest + 2, dest, strlen(dest) + 1); // Shift right
printf("%s\n", dest); // "HeHello"
// Compare memory
if (memcmp(src, dest, 5) == 0) {
printf("Memory regions match\n");
}
return 0;
}
```
**Clay's Approach:**
```c
// Clay uses custom memory functions when needed
static inline void Clay__MemoryCopy(
void *dest,
const void *src,
size_t size
) {
char *d = (char*)dest;
const char *s = (const char*)src;
for (size_t i = 0; i < size; i++) {
d[i] = s[i];
}
}
```
---
## 21.5 math.h - Mathematical Functions
```c
#include <math.h>
#include <stdio.h>
int main(void) {
// Power and roots
printf("2^3 = %.0f\n", pow(2, 3)); // 8
printf("sqrt(16) = %.0f\n", sqrt(16)); // 4
printf("cbrt(27) = %.0f\n", cbrt(27)); // 3
// Trigonometry
printf("sin(π/2) = %.1f\n", sin(M_PI / 2)); // 1.0
printf("cos(0) = %.1f\n", cos(0)); // 1.0
printf("tan(π/4) = %.1f\n", tan(M_PI / 4)); // 1.0
// Rounding
printf("ceil(3.2) = %.0f\n", ceil(3.2)); // 4
printf("floor(3.8) = %.0f\n", floor(3.8)); // 3
printf("round(3.5) = %.0f\n", round(3.5)); // 4
// Absolute value
printf("fabs(-5.5) = %.1f\n", fabs(-5.5)); // 5.5
printf("abs(-5) = %d\n", abs(-5)); // 5
// Logarithms
printf("log(e) = %.1f\n", log(M_E)); // 1.0
printf("log10(100) = %.0f\n", log10(100)); // 2
// Exponential
printf("exp(1) = %.2f\n", exp(1)); // 2.72 (e)
return 0;
}
```
**Clay's Implementation:**
```c
// Clay implements its own min/max (no stdlib needed)
static inline float Clay__Min(float a, float b) {
return a < b ? a : b;
}
static inline float Clay__Max(float a, float b) {
return a > b ? a : b;
}
static inline float Clay__Clamp(float value, float min, float max) {
return Clay__Max(min, Clay__Min(value, max));
}
```
---
## 21.6 ctype.h - Character Handling
```c
#include <ctype.h>
#include <stdio.h>
int main(void) {
char ch = 'A';
// Character testing
if (isalpha(ch)) printf("Letter\n");
if (isdigit(ch)) printf("Digit\n");
if (isalnum(ch)) printf("Alphanumeric\n");
if (isupper(ch)) printf("Uppercase\n");
if (islower(ch)) printf("Lowercase\n");
if (isspace(ch)) printf("Whitespace\n");
if (ispunct(ch)) printf("Punctuation\n");
// Character conversion
printf("Upper: %c\n", toupper('a')); // 'A'
printf("Lower: %c\n", tolower('A')); // 'a'
// Practical example: validate identifier
int isValidIdentifier(const char *str) {
if (!isalpha(str[0]) && str[0] != '_') {
return 0; // Must start with letter or _
}
for (int i = 1; str[i] != '\0'; i++) {
if (!isalnum(str[i]) && str[i] != '_') {
return 0;
}
}
return 1;
}
printf("valid_name: %d\n", isValidIdentifier("valid_name")); // 1
printf("123invalid: %d\n", isValidIdentifier("123invalid")); // 0
return 0;
}
```
---
## 21.7 time.h - Time and Date
```c
#include <time.h>
#include <stdio.h>
int main(void) {
// Current time
time_t now = time(NULL);
printf("Seconds since epoch: %ld\n", now);
// Convert to readable format
struct tm *timeinfo = localtime(&now);
printf("Current time: %s", asctime(timeinfo));
// Format time
char buffer[80];
strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", timeinfo);
printf("Formatted: %s\n", buffer);
// Measure execution time
clock_t start = clock();
// Do some work
for (int i = 0; i < 1000000; i++) {
// Busy work
}
clock_t end = clock();
double cpu_time = ((double)(end - start)) / CLOCKS_PER_SEC;
printf("CPU time: %.6f seconds\n", cpu_time);
// Sleep (POSIX)
// sleep(1); // Sleep 1 second
return 0;
}
```
---
## 21.8 assert.h - Debugging
```c
#include <assert.h>
#include <stdio.h>
int divide(int a, int b) {
assert(b != 0); // Crash if b is 0 (in debug builds)
return a / b;
}
int main(void) {
int result = divide(10, 2); // OK
printf("Result: %d\n", result);
// result = divide(10, 0); // Crashes with error message
// Disable asserts in release
// Compile with: gcc -DNDEBUG program.c
return 0;
}
```
**Clay's Approach:**
```c
// Clay has custom error handling
#define CLAY__ASSERT(condition) \
if (!(condition)) { \
Clay__ErrorHandler(...); \
}
```
---
## 21.9 stdint.h - Fixed-Width Integers
```c
#include <stdint.h>
#include <stdio.h>
int main(void) {
// Exact-width integers
int8_t i8 = 127; // -128 to 127
uint8_t u8 = 255; // 0 to 255
int16_t i16 = 32767; // -32768 to 32767
uint16_t u16 = 65535; // 0 to 65535
int32_t i32 = 2147483647;
uint32_t u32 = 4294967295;
int64_t i64 = 9223372036854775807;
uint64_t u64 = 18446744073709551615ULL;
// Pointer-sized integers
intptr_t iptr; // Can hold pointer
uintptr_t uptr;
// Fast types (at least N bits)
int_fast32_t fast32; // Fast 32-bit (may be 64-bit)
int_least32_t least32; // At least 32-bit (may be 32+)
// Print with proper format specifiers
printf("int32: %" PRId32 "\n", i32);
printf("uint64: %" PRIu64 "\n", u64);
return 0;
}
```
**Clay uses fixed-width types extensively:**
```c
typedef struct {
int32_t capacity; // Exactly 32 bits
int32_t length;
uint32_t *internalArray;
} Clay__int32_tArray;
```
---
## 21.10 stdbool.h - Boolean Type
```c
#include <stdbool.h>
#include <stdio.h>
int main(void) {
bool isActive = true;
bool isValid = false;
if (isActive) {
printf("Active!\n");
}
// Boolean operations
bool result = isActive && !isValid; // true
return 0;
}
```
**Pre-C99 approach:**
```c
typedef enum {
false = 0,
true = 1
} bool;
```
---
## 21.11 limits.h - Implementation Limits
```c
#include <limits.h>
#include <stdio.h>
int main(void) {
printf("CHAR_BIT: %d\n", CHAR_BIT); // 8
printf("CHAR_MIN: %d\n", CHAR_MIN);
printf("CHAR_MAX: %d\n", CHAR_MAX);
printf("INT_MIN: %d\n", INT_MIN); // -2147483648
printf("INT_MAX: %d\n", INT_MAX); // 2147483647
printf("LONG_MAX: %ld\n", LONG_MAX);
// Check for overflow
int x = INT_MAX;
if (x + 1 < x) {
printf("Overflow detected!\n");
}
return 0;
}
```
---
## 21.12 Key Concepts Learned
- ✅ stdio.h for I/O operations
- ✅ stdlib.h for memory and utilities
- ✅ string.h for string manipulation
- ✅ math.h for mathematical functions
- ✅ ctype.h for character handling
- ✅ time.h for time/date operations
- ✅ assert.h for debugging
- ✅ stdint.h for fixed-width types
- ✅ stdbool.h for boolean type
- ✅ Clay's zero-dependency approach
---
## Practice Exercises
1. Write a program to read a file and count words
2. Implement your own strlen without using stdlib
3. Create a simple calculator using scanf and math.h
4. Build a random password generator
5. Make a function to format time as "X days, Y hours, Z minutes"
6. Implement case-insensitive string comparison
7. Create a memory pool allocator (like Clay's arena)
8. Write a benchmark utility using clock()

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# Chapter 22: File I/O in C
## Complete Guide with Clay Library Examples
---
## 22.1 Introduction to File I/O
C provides file operations through `stdio.h`:
- Open files
- Read/write data
- Close files
- Navigate file position
- Check file status
**Clay's Approach:** Clay doesn't do file I/O - it's a UI layout library. But applications using Clay need file operations for saving/loading UI state, configurations, etc.
---
## 22.2 Opening and Closing Files
### Basic File Operations
```c
#include <stdio.h>
int main(void) {
FILE *file;
// Open file for writing
file = fopen("output.txt", "w");
if (file == NULL) {
printf("Error opening file!\n");
return 1;
}
// Write to file
fprintf(file, "Hello, File!\n");
// Close file
fclose(file);
return 0;
}
```
### File Modes
| Mode | Description | Creates if not exists | Truncates existing |
|------|-------------|----------------------|-------------------|
| `"r"` | Read only | No | No |
| `"w"` | Write only | Yes | Yes |
| `"a"` | Append | Yes | No |
| `"r+"` | Read/Write | No | No |
| `"w+"` | Read/Write | Yes | Yes |
| `"a+"` | Read/Append | Yes | No |
| `"rb"` | Read binary | No | No |
| `"wb"` | Write binary | Yes | Yes |
```c
FILE *fr = fopen("input.txt", "r"); // Read text
FILE *fw = fopen("output.txt", "w"); // Write text
FILE *fa = fopen("log.txt", "a"); // Append text
FILE *fb = fopen("data.bin", "rb"); // Read binary
```
---
## 22.3 Writing to Files
### fprintf - Formatted Output
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("data.txt", "w");
if (file == NULL) {
return 1;
}
int age = 25;
float height = 5.9f;
char name[] = "John";
// Write formatted data
fprintf(file, "Name: %s\n", name);
fprintf(file, "Age: %d\n", age);
fprintf(file, "Height: %.1f\n", height);
fclose(file);
return 0;
}
```
### fputs - Write String
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("output.txt", "w");
if (file == NULL) return 1;
fputs("Line 1\n", file);
fputs("Line 2\n", file);
fputs("Line 3\n", file);
fclose(file);
return 0;
}
```
### fputc - Write Character
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("output.txt", "w");
if (file == NULL) return 1;
fputc('H', file);
fputc('i', file);
fputc('\n', file);
fclose(file);
return 0;
}
```
### fwrite - Write Binary Data
```c
#include <stdio.h>
typedef struct {
int id;
char name[50];
float salary;
} Employee;
int main(void) {
FILE *file = fopen("employees.dat", "wb");
if (file == NULL) return 1;
Employee emp = {1, "John Doe", 50000.0f};
// Write struct to binary file
size_t written = fwrite(&emp, sizeof(Employee), 1, file);
if (written != 1) {
printf("Write error!\n");
}
fclose(file);
return 0;
}
```
---
## 22.4 Reading from Files
### fscanf - Formatted Input
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("data.txt", "r");
if (file == NULL) return 1;
char name[50];
int age;
float height;
// Read formatted data
fscanf(file, "Name: %s\n", name);
fscanf(file, "Age: %d\n", &age);
fscanf(file, "Height: %f\n", &height);
printf("Name: %s, Age: %d, Height: %.1f\n", name, age, height);
fclose(file);
return 0;
}
```
### fgets - Read Line
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("input.txt", "r");
if (file == NULL) return 1;
char buffer[256];
// Read line by line
while (fgets(buffer, sizeof(buffer), file) != NULL) {
printf("%s", buffer);
}
fclose(file);
return 0;
}
```
### fgetc - Read Character
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("input.txt", "r");
if (file == NULL) return 1;
int ch;
// Read character by character
while ((ch = fgetc(file)) != EOF) {
putchar(ch);
}
fclose(file);
return 0;
}
```
### fread - Read Binary Data
```c
#include <stdio.h>
typedef struct {
int id;
char name[50];
float salary;
} Employee;
int main(void) {
FILE *file = fopen("employees.dat", "rb");
if (file == NULL) return 1;
Employee emp;
// Read struct from binary file
size_t read = fread(&emp, sizeof(Employee), 1, file);
if (read == 1) {
printf("ID: %d, Name: %s, Salary: %.2f\n",
emp.id, emp.name, emp.salary);
}
fclose(file);
return 0;
}
```
---
## 22.5 File Position
### ftell - Get Position
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("data.txt", "r");
if (file == NULL) return 1;
// Get current position
long pos = ftell(file);
printf("Position: %ld\n", pos); // 0 (at start)
// Read some data
char buffer[10];
fgets(buffer, sizeof(buffer), file);
// Get new position
pos = ftell(file);
printf("Position after read: %ld\n", pos);
fclose(file);
return 0;
}
```
### fseek - Set Position
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("data.txt", "r");
if (file == NULL) return 1;
// Seek to end
fseek(file, 0, SEEK_END);
long size = ftell(file);
printf("File size: %ld bytes\n", size);
// Seek to beginning
fseek(file, 0, SEEK_SET);
// Seek forward 10 bytes
fseek(file, 10, SEEK_CUR);
fclose(file);
return 0;
}
```
**Seek origins:**
- `SEEK_SET` - Beginning of file
- `SEEK_CUR` - Current position
- `SEEK_END` - End of file
### rewind - Reset to Beginning
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("data.txt", "r");
if (file == NULL) return 1;
// Read file
char buffer[100];
fgets(buffer, sizeof(buffer), file);
// Go back to start
rewind(file); // Same as fseek(file, 0, SEEK_SET)
// Read again
fgets(buffer, sizeof(buffer), file);
fclose(file);
return 0;
}
```
---
## 22.6 File Status
### feof - Check End of File
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("input.txt", "r");
if (file == NULL) return 1;
char ch;
while (!feof(file)) {
ch = fgetc(file);
if (ch != EOF) {
putchar(ch);
}
}
fclose(file);
return 0;
}
```
### ferror - Check Errors
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("output.txt", "w");
if (file == NULL) return 1;
fprintf(file, "Test\n");
if (ferror(file)) {
printf("Error writing to file!\n");
clearerr(file); // Clear error flag
}
fclose(file);
return 0;
}
```
### File Existence
```c
#include <stdio.h>
int fileExists(const char *filename) {
FILE *file = fopen(filename, "r");
if (file != NULL) {
fclose(file);
return 1;
}
return 0;
}
int main(void) {
if (fileExists("config.txt")) {
printf("Config file found!\n");
} else {
printf("Config file not found!\n");
}
return 0;
}
```
---
## 22.7 Practical Examples
### Copy File
```c
#include <stdio.h>
int copyFile(const char *src, const char *dest) {
FILE *source = fopen(src, "rb");
if (source == NULL) return 0;
FILE *target = fopen(dest, "wb");
if (target == NULL) {
fclose(source);
return 0;
}
// Copy buffer by buffer
char buffer[1024];
size_t bytes;
while ((bytes = fread(buffer, 1, sizeof(buffer), source)) > 0) {
fwrite(buffer, 1, bytes, target);
}
fclose(source);
fclose(target);
return 1;
}
int main(void) {
if (copyFile("input.txt", "output.txt")) {
printf("File copied successfully!\n");
}
return 0;
}
```
### Count Lines in File
```c
#include <stdio.h>
int countLines(const char *filename) {
FILE *file = fopen(filename, "r");
if (file == NULL) return -1;
int lines = 0;
int ch;
while ((ch = fgetc(file)) != EOF) {
if (ch == '\n') {
lines++;
}
}
fclose(file);
return lines;
}
int main(void) {
int lines = countLines("input.txt");
printf("Lines: %d\n", lines);
return 0;
}
```
### Read Entire File
```c
#include <stdio.h>
#include <stdlib.h>
char* readFile(const char *filename, size_t *size) {
FILE *file = fopen(filename, "rb");
if (file == NULL) return NULL;
// Get file size
fseek(file, 0, SEEK_END);
long filesize = ftell(file);
rewind(file);
// Allocate buffer
char *buffer = (char*)malloc(filesize + 1);
if (buffer == NULL) {
fclose(file);
return NULL;
}
// Read entire file
size_t read = fread(buffer, 1, filesize, file);
buffer[read] = '\0'; // Null terminate
if (size != NULL) {
*size = read;
}
fclose(file);
return buffer;
}
int main(void) {
size_t size;
char *content = readFile("input.txt", &size);
if (content != NULL) {
printf("Content (%zu bytes):\n%s\n", size, content);
free(content);
}
return 0;
}
```
---
## 22.8 Configuration File (Clay Example)
### Save Clay UI Configuration
```c
#include <stdio.h>
typedef struct {
float width;
float height;
int layoutDirection;
int padding;
} Clay_LayoutConfig;
int saveLayoutConfig(const char *filename, Clay_LayoutConfig *config) {
FILE *file = fopen(filename, "w");
if (file == NULL) return 0;
fprintf(file, "width=%.2f\n", config->width);
fprintf(file, "height=%.2f\n", config->height);
fprintf(file, "layoutDirection=%d\n", config->layoutDirection);
fprintf(file, "padding=%d\n", config->padding);
fclose(file);
return 1;
}
int loadLayoutConfig(const char *filename, Clay_LayoutConfig *config) {
FILE *file = fopen(filename, "r");
if (file == NULL) return 0;
fscanf(file, "width=%f\n", &config->width);
fscanf(file, "height=%f\n", &config->height);
fscanf(file, "layoutDirection=%d\n", &config->layoutDirection);
fscanf(file, "padding=%d\n", &config->padding);
fclose(file);
return 1;
}
int main(void) {
Clay_LayoutConfig config = {
.width = 800.0f,
.height = 600.0f,
.layoutDirection = 0,
.padding = 16
};
// Save config
saveLayoutConfig("layout.cfg", &config);
// Load config
Clay_LayoutConfig loaded = {0};
if (loadLayoutConfig("layout.cfg", &loaded)) {
printf("Loaded: %.0fx%.0f, dir=%d, pad=%d\n",
loaded.width, loaded.height,
loaded.layoutDirection, loaded.padding);
}
return 0;
}
```
---
## 22.9 Binary File Format
### Save/Load Array
```c
#include <stdio.h>
#include <stdlib.h>
typedef struct {
int count;
float *values;
} FloatArray;
int saveFloatArray(const char *filename, FloatArray *arr) {
FILE *file = fopen(filename, "wb");
if (file == NULL) return 0;
// Write count
fwrite(&arr->count, sizeof(int), 1, file);
// Write values
fwrite(arr->values, sizeof(float), arr->count, file);
fclose(file);
return 1;
}
FloatArray* loadFloatArray(const char *filename) {
FILE *file = fopen(filename, "rb");
if (file == NULL) return NULL;
FloatArray *arr = (FloatArray*)malloc(sizeof(FloatArray));
// Read count
fread(&arr->count, sizeof(int), 1, file);
// Allocate and read values
arr->values = (float*)malloc(arr->count * sizeof(float));
fread(arr->values, sizeof(float), arr->count, file);
fclose(file);
return arr;
}
int main(void) {
// Create array
FloatArray arr;
arr.count = 5;
arr.values = (float*)malloc(5 * sizeof(float));
for (int i = 0; i < 5; i++) {
arr.values[i] = i * 1.5f;
}
// Save
saveFloatArray("data.bin", &arr);
// Load
FloatArray *loaded = loadFloatArray("data.bin");
if (loaded != NULL) {
printf("Loaded %d values:\n", loaded->count);
for (int i = 0; i < loaded->count; i++) {
printf("%.1f ", loaded->values[i]);
}
printf("\n");
free(loaded->values);
free(loaded);
}
free(arr.values);
return 0;
}
```
---
## 22.10 Error Handling
### Robust File Operations
```c
#include <stdio.h>
#include <errno.h>
#include <string.h>
typedef enum {
FILE_OK,
FILE_ERROR_OPEN,
FILE_ERROR_READ,
FILE_ERROR_WRITE
} FileError;
FileError writeData(const char *filename, const char *data) {
FILE *file = fopen(filename, "w");
if (file == NULL) {
printf("Open error: %s\n", strerror(errno));
return FILE_ERROR_OPEN;
}
if (fputs(data, file) == EOF) {
printf("Write error: %s\n", strerror(errno));
fclose(file);
return FILE_ERROR_WRITE;
}
fclose(file);
return FILE_OK;
}
int main(void) {
FileError err = writeData("output.txt", "Hello!\n");
if (err != FILE_OK) {
printf("Error code: %d\n", err);
}
return 0;
}
```
---
## 22.11 Temporary Files
```c
#include <stdio.h>
int main(void) {
// Create temporary file
FILE *temp = tmpfile();
if (temp == NULL) {
printf("Error creating temp file!\n");
return 1;
}
// Use temp file
fprintf(temp, "Temporary data\n");
rewind(temp);
char buffer[100];
fgets(buffer, sizeof(buffer), temp);
printf("Read: %s", buffer);
// File automatically deleted on close
fclose(temp);
return 0;
}
```
---
## 22.12 Buffer Control
### Set Buffer Mode
```c
#include <stdio.h>
int main(void) {
FILE *file = fopen("output.txt", "w");
if (file == NULL) return 1;
// Disable buffering
setbuf(file, NULL);
// Or set custom buffer
char buffer[BUFSIZ];
setvbuf(file, buffer, _IOFBF, BUFSIZ); // Full buffering
// _IONBF = No buffering
// _IOLBF = Line buffering
// _IOFBF = Full buffering
fprintf(file, "Data\n");
// Force write buffer
fflush(file);
fclose(file);
return 0;
}
```
---
## 22.13 Key Concepts Learned
- ✅ Opening and closing files
- ✅ File modes (read, write, append, binary)
- ✅ Writing: fprintf, fputs, fputc, fwrite
- ✅ Reading: fscanf, fgets, fgetc, fread
- ✅ File position: ftell, fseek, rewind
- ✅ File status: feof, ferror
- ✅ Binary file operations
- ✅ Error handling
- ✅ Configuration files
- ✅ Buffer control
---
## Practice Exercises
1. Create a text editor that can save/load files
2. Build a CSV parser and writer
3. Implement a simple database using binary files
4. Create a log file system with timestamps
5. Write a file encryption/decryption program
6. Build a file comparison utility (diff)
7. Implement a config file parser (INI format)
8. Create a file compression utility (run-length encoding)

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# Chapter 23: Command-Line Arguments in C
## Complete Guide with Clay Library Examples
---
## 23.1 Introduction to Command-Line Arguments
When you run a program from the terminal:
```bash
./program arg1 arg2 arg3
```
C provides access to these arguments through `main`:
```c
int main(int argc, char *argv[]) {
// argc = argument count
// argv = argument vector (array of strings)
return 0;
}
```
**Parts:**
- `argc` - Number of arguments (including program name)
- `argv` - Array of argument strings
- `argv[0]` - Program name
- `argv[1]` to `argv[argc-1]` - Actual arguments
- `argv[argc]` - NULL pointer
---
## 23.2 Basic Example
```c
#include <stdio.h>
int main(int argc, char *argv[]) {
printf("Program name: %s\n", argv[0]);
printf("Argument count: %d\n", argc);
printf("Arguments:\n");
for (int i = 0; i < argc; i++) {
printf(" argv[%d] = %s\n", i, argv[i]);
}
return 0;
}
```
**Running:**
```bash
$ ./program hello world 123
Program name: ./program
Argument count: 4
Arguments:
argv[0] = ./program
argv[1] = hello
argv[2] = world
argv[3] = 123
```
---
## 23.3 Processing Arguments
### Check Argument Count
```c
#include <stdio.h>
int main(int argc, char *argv[]) {
if (argc != 3) {
printf("Usage: %s <name> <age>\n", argv[0]);
return 1;
}
char *name = argv[1];
int age = atoi(argv[2]); // Convert string to int
printf("Name: %s, Age: %d\n", name, age);
return 0;
}
```
**Running:**
```bash
$ ./program John 25
Name: John, Age: 25
$ ./program John
Usage: ./program <name> <age>
```
---
## 23.4 Parsing Numeric Arguments
```c
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[]) {
if (argc != 4) {
printf("Usage: %s <a> <b> <c>\n", argv[0]);
return 1;
}
// Convert arguments to numbers
int a = atoi(argv[1]); // Integer
long b = atol(argv[2]); // Long
double c = atof(argv[3]); // Double
printf("a = %d\n", a);
printf("b = %ld\n", b);
printf("c = %.2f\n", c);
return 0;
}
```
**Running:**
```bash
$ ./program 10 1000000 3.14
a = 10
b = 1000000
c = 3.14
```
---
## 23.5 Command-Line Flags
### Simple Flags
```c
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[]) {
int verbose = 0;
int debug = 0;
// Check for flags
for (int i = 1; i < argc; i++) {
if (strcmp(argv[i], "-v") == 0 ||
strcmp(argv[i], "--verbose") == 0) {
verbose = 1;
}
else if (strcmp(argv[i], "-d") == 0 ||
strcmp(argv[i], "--debug") == 0) {
debug = 1;
}
}
printf("Verbose: %s\n", verbose ? "ON" : "OFF");
printf("Debug: %s\n", debug ? "ON" : "OFF");
return 0;
}
```
**Running:**
```bash
$ ./program -v
Verbose: ON
Debug: OFF
$ ./program -v -d
Verbose: ON
Debug: ON
$ ./program --verbose --debug
Verbose: ON
Debug: ON
```
---
## 23.6 Flags with Values
```c
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(int argc, char *argv[]) {
char *output = "output.txt"; // Default
int level = 1; // Default
for (int i = 1; i < argc; i++) {
if (strcmp(argv[i], "-o") == 0 && i + 1 < argc) {
output = argv[++i]; // Next argument is the value
}
else if (strcmp(argv[i], "-l") == 0 && i + 1 < argc) {
level = atoi(argv[++i]);
}
}
printf("Output: %s\n", output);
printf("Level: %d\n", level);
return 0;
}
```
**Running:**
```bash
$ ./program -o result.txt -l 5
Output: result.txt
Level: 5
$ ./program
Output: output.txt
Level: 1
```
---
## 23.7 getopt for Option Parsing
POSIX provides `getopt` for standard option parsing:
```c
#include <stdio.h>
#include <unistd.h> // POSIX
int main(int argc, char *argv[]) {
int opt;
int verbose = 0;
char *output = NULL;
int level = 1;
// Parse options
while ((opt = getopt(argc, argv, "vo:l:")) != -1) {
switch (opt) {
case 'v':
verbose = 1;
break;
case 'o':
output = optarg; // Option argument
break;
case 'l':
level = atoi(optarg);
break;
case '?':
printf("Unknown option: %c\n", optopt);
return 1;
}
}
// Process remaining arguments
for (int i = optind; i < argc; i++) {
printf("Non-option arg: %s\n", argv[i]);
}
printf("Verbose: %d\n", verbose);
printf("Output: %s\n", output ? output : "none");
printf("Level: %d\n", level);
return 0;
}
```
**Running:**
```bash
$ ./program -v -o test.txt -l 3 file1 file2
Non-option arg: file1
Non-option arg: file2
Verbose: 1
Output: test.txt
Level: 3
```
---
## 23.8 Clay Example: UI Configuration
Imagine a Clay-based application with command-line options:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct {
int width;
int height;
int fullscreen;
char *title;
} AppConfig;
void printUsage(const char *programName) {
printf("Usage: %s [options]\n", programName);
printf("Options:\n");
printf(" -w <width> Window width (default: 800)\n");
printf(" -h <height> Window height (default: 600)\n");
printf(" -f Fullscreen mode\n");
printf(" -t <title> Window title\n");
printf(" --help Show this help\n");
}
int parseArgs(int argc, char *argv[], AppConfig *config) {
// Defaults
config->width = 800;
config->height = 600;
config->fullscreen = 0;
config->title = "Clay Application";
for (int i = 1; i < argc; i++) {
if (strcmp(argv[i], "-w") == 0 && i + 1 < argc) {
config->width = atoi(argv[++i]);
}
else if (strcmp(argv[i], "-h") == 0 && i + 1 < argc) {
config->height = atoi(argv[++i]);
}
else if (strcmp(argv[i], "-f") == 0) {
config->fullscreen = 1;
}
else if (strcmp(argv[i], "-t") == 0 && i + 1 < argc) {
config->title = argv[++i];
}
else if (strcmp(argv[i], "--help") == 0) {
return 0; // Show help
}
else {
printf("Unknown option: %s\n", argv[i]);
return 0;
}
}
return 1;
}
int main(int argc, char *argv[]) {
AppConfig config;
if (!parseArgs(argc, argv, &config)) {
printUsage(argv[0]);
return 1;
}
printf("Starting Clay application:\n");
printf(" Size: %dx%d\n", config.width, config.height);
printf(" Fullscreen: %s\n", config.fullscreen ? "Yes" : "No");
printf(" Title: %s\n", config.title);
// Initialize Clay with config
// Clay_Dimensions screenSize = {config.width, config.height};
// Clay_Initialize(...);
return 0;
}
```
**Running:**
```bash
$ ./clay_app -w 1024 -h 768 -f -t "My UI"
Starting Clay application:
Size: 1024x768
Fullscreen: Yes
Title: My UI
$ ./clay_app --help
Usage: ./clay_app [options]
Options:
-w <width> Window width (default: 800)
-h <height> Window height (default: 600)
-f Fullscreen mode
-t <title> Window title
--help Show this help
```
---
## 23.9 Subcommands (git-style)
```c
#include <stdio.h>
#include <string.h>
void cmd_init(int argc, char *argv[]) {
printf("Initializing...\n");
}
void cmd_add(int argc, char *argv[]) {
if (argc < 1) {
printf("Error: add requires a file argument\n");
return;
}
printf("Adding: %s\n", argv[0]);
}
void cmd_commit(int argc, char *argv[]) {
char *message = "Default message";
if (argc >= 2 && strcmp(argv[0], "-m") == 0) {
message = argv[1];
}
printf("Committing: %s\n", message);
}
int main(int argc, char *argv[]) {
if (argc < 2) {
printf("Usage: %s <command> [args]\n", argv[0]);
printf("Commands: init, add, commit\n");
return 1;
}
char *command = argv[1];
int cmd_argc = argc - 2;
char **cmd_argv = argv + 2;
if (strcmp(command, "init") == 0) {
cmd_init(cmd_argc, cmd_argv);
}
else if (strcmp(command, "add") == 0) {
cmd_add(cmd_argc, cmd_argv);
}
else if (strcmp(command, "commit") == 0) {
cmd_commit(cmd_argc, cmd_argv);
}
else {
printf("Unknown command: %s\n", command);
return 1;
}
return 0;
}
```
**Running:**
```bash
$ ./mygit init
Initializing...
$ ./mygit add file.txt
Adding: file.txt
$ ./mygit commit -m "Initial commit"
Committing: Initial commit
```
---
## 23.10 Environment Variables
Access environment variables alongside arguments:
```c
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[], char *envp[]) {
printf("Arguments:\n");
for (int i = 0; i < argc; i++) {
printf(" %s\n", argv[i]);
}
printf("\nEnvironment Variables:\n");
for (int i = 0; envp[i] != NULL; i++) {
printf(" %s\n", envp[i]);
}
// Or use getenv
char *home = getenv("HOME");
printf("\nHOME: %s\n", home);
return 0;
}
```
---
## 23.11 Argument Validation
### Robust Argument Parser
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <errno.h>
int parseInteger(const char *str, int *out) {
char *endptr;
errno = 0;
long val = strtol(str, &endptr, 10);
if (errno == ERANGE || val > INT_MAX || val < INT_MIN) {
return 0; // Out of range
}
if (endptr == str || *endptr != '\0') {
return 0; // Not a valid number
}
*out = (int)val;
return 1;
}
int main(int argc, char *argv[]) {
if (argc != 2) {
printf("Usage: %s <number>\n", argv[0]);
return 1;
}
int value;
if (!parseInteger(argv[1], &value)) {
printf("Error: '%s' is not a valid integer\n", argv[1]);
return 1;
}
printf("Valid integer: %d\n", value);
return 0;
}
```
---
## 23.12 Configuration Priority
Combine defaults, config files, and command-line arguments:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct {
int port;
char *host;
int debug;
} ServerConfig;
void setDefaults(ServerConfig *config) {
config->port = 8080;
config->host = "localhost";
config->debug = 0;
}
void loadConfigFile(ServerConfig *config, const char *filename) {
FILE *file = fopen(filename, "r");
if (file == NULL) return;
char line[256];
while (fgets(line, sizeof(line), file)) {
if (strncmp(line, "port=", 5) == 0) {
config->port = atoi(line + 5);
}
else if (strncmp(line, "host=", 5) == 0) {
config->host = strdup(line + 5);
// Remove newline
config->host[strcspn(config->host, "\n")] = 0;
}
}
fclose(file);
}
void parseArgs(ServerConfig *config, int argc, char *argv[]) {
for (int i = 1; i < argc; i++) {
if (strcmp(argv[i], "-p") == 0 && i + 1 < argc) {
config->port = atoi(argv[++i]);
}
else if (strcmp(argv[i], "-h") == 0 && i + 1 < argc) {
config->host = argv[++i];
}
else if (strcmp(argv[i], "-d") == 0) {
config->debug = 1;
}
}
}
int main(int argc, char *argv[]) {
ServerConfig config;
// Priority: defaults < config file < command line
setDefaults(&config);
loadConfigFile(&config, "server.cfg");
parseArgs(&config, argc, argv);
printf("Server configuration:\n");
printf(" Host: %s\n", config.host);
printf(" Port: %d\n", config.port);
printf(" Debug: %s\n", config.debug ? "ON" : "OFF");
return 0;
}
```
---
## 23.13 Wildcard Arguments
Handle wildcards expanded by shell:
```c
#include <stdio.h>
int main(int argc, char *argv[]) {
if (argc < 2) {
printf("Usage: %s <files...>\n", argv[0]);
return 1;
}
printf("Processing %d files:\n", argc - 1);
for (int i = 1; i < argc; i++) {
printf(" - %s\n", argv[i]);
}
return 0;
}
```
**Running:**
```bash
$ ./program *.txt
Processing 3 files:
- file1.txt
- file2.txt
- file3.txt
```
---
## 23.14 Interactive vs Batch Mode
```c
#include <stdio.h>
#include <string.h>
int interactiveMode(void) {
char input[100];
while (1) {
printf("> ");
if (fgets(input, sizeof(input), stdin) == NULL) {
break;
}
// Remove newline
input[strcspn(input, "\n")] = 0;
if (strcmp(input, "quit") == 0) {
break;
}
printf("You entered: %s\n", input);
}
return 0;
}
int batchMode(const char *filename) {
FILE *file = fopen(filename, "r");
if (file == NULL) {
printf("Error: Cannot open %s\n", filename);
return 1;
}
char line[100];
while (fgets(line, sizeof(line), file)) {
// Process line
printf("Processing: %s", line);
}
fclose(file);
return 0;
}
int main(int argc, char *argv[]) {
if (argc == 1) {
// No arguments: interactive mode
printf("Interactive mode (type 'quit' to exit)\n");
return interactiveMode();
}
else {
// Arguments provided: batch mode
for (int i = 1; i < argc; i++) {
printf("Processing file: %s\n", argv[i]);
batchMode(argv[i]);
}
return 0;
}
}
```
---
## 23.15 Clay Application Example
Complete Clay application with arguments:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// #define CLAY_IMPLEMENTATION
// #include "clay.h"
typedef struct {
int width;
int height;
int fps;
char *layout_file;
int benchmark;
} ClayAppConfig;
void printHelp(const char *program) {
printf("Usage: %s [options] [layout_file]\n", program);
printf("\nOptions:\n");
printf(" -w, --width <N> Window width (default: 1024)\n");
printf(" -h, --height <N> Window height (default: 768)\n");
printf(" --fps <N> Target FPS (default: 60)\n");
printf(" --benchmark Run in benchmark mode\n");
printf(" --help Show this help\n");
printf("\nExamples:\n");
printf(" %s --width 1920 --height 1080 layout.clay\n", program);
printf(" %s --benchmark\n", program);
}
int parseArguments(int argc, char *argv[], ClayAppConfig *config) {
// Defaults
config->width = 1024;
config->height = 768;
config->fps = 60;
config->layout_file = NULL;
config->benchmark = 0;
for (int i = 1; i < argc; i++) {
if (strcmp(argv[i], "-w") == 0 || strcmp(argv[i], "--width") == 0) {
if (++i >= argc) return 0;
config->width = atoi(argv[i]);
}
else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--height") == 0) {
if (++i >= argc) return 0;
config->height = atoi(argv[i]);
}
else if (strcmp(argv[i], "--fps") == 0) {
if (++i >= argc) return 0;
config->fps = atoi(argv[i]);
}
else if (strcmp(argv[i], "--benchmark") == 0) {
config->benchmark = 1;
}
else if (strcmp(argv[i], "--help") == 0) {
return 0;
}
else if (argv[i][0] != '-') {
config->layout_file = argv[i];
}
else {
printf("Unknown option: %s\n", argv[i]);
return 0;
}
}
return 1;
}
int main(int argc, char *argv[]) {
ClayAppConfig config;
if (!parseArguments(argc, argv, &config)) {
printHelp(argv[0]);
return 1;
}
printf("Clay Application Starting:\n");
printf(" Resolution: %dx%d\n", config.width, config.height);
printf(" Target FPS: %d\n", config.fps);
printf(" Benchmark: %s\n", config.benchmark ? "Yes" : "No");
if (config.layout_file) {
printf(" Layout File: %s\n", config.layout_file);
}
// Initialize Clay
// Clay_Dimensions windowSize = {config.width, config.height};
// Clay_Initialize(...);
// Main loop...
return 0;
}
```
---
## 23.16 Key Concepts Learned
- ✅ argc and argv basics
- ✅ Processing command-line arguments
- ✅ Parsing numeric arguments
- ✅ Command-line flags
- ✅ Flags with values
- ✅ getopt for option parsing
- ✅ Subcommands
- ✅ Environment variables
- ✅ Argument validation
- ✅ Configuration priority
- ✅ Interactive vs batch mode
- ✅ Clay application with arguments
---
## Practice Exercises
1. Build a calculator that accepts expressions as arguments
2. Create a file search utility with filtering options
3. Implement a CSV processor with column selection
4. Build a simple HTTP server with configurable port
5. Create a code formatter with style options
6. Implement a task manager CLI (add, list, complete)
7. Build an image converter with format options
8. Create a benchmarking tool with various options

455
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@ -0,0 +1,455 @@
# Complete C Programming Guide Using Clay Library
## Master C Programming Step-by-Step with Real-World Examples
This comprehensive guide teaches you C programming from basics to advanced concepts, using the professional Clay UI layout library as a real-world reference throughout.
---
## 📚 What You'll Learn
- ✅ **All C fundamentals** - Variables, operators, control flow, loops
- ✅ **Memory management** - Pointers, arrays, dynamic allocation
- ✅ **Advanced concepts** - Macros, bit manipulation, recursion
- ✅ **Real-world patterns** - As demonstrated by Clay library
- ✅ **Professional practices** - Code organization, error handling
- ✅ **Practical applications** - File I/O, command-line tools
---
## 📖 Complete Tutorial Index
### Part 1: Fundamentals (Main Guide)
**File: `LEARNING_C_WITH_CLAY.md`**
1. **Chapter 1: C Basics** - Your first program, includes, comments
2. **Chapter 2: Variables and Data Types** - int, float, char, fixed-width types
3. **Chapter 3: Operators** - Arithmetic, logical, bitwise, ternary
4. **Chapter 4: Control Flow** - if/else, switch, goto
5. **Chapter 5: Loops** - while, for, do-while, break, continue
6. **Chapter 6: Functions** - Declaration, definition, parameters, recursion
7. **Chapter 7: Pointers** - Memory addresses, dereferencing, pointer arithmetic
8. **Chapter 8: Structs and Typedef** - Grouping data, nested structs, designated initializers
9. **Chapter 9: Arrays** - Static arrays, multidimensional, relationship with pointers
10. **Chapter 10: Strings** - C strings, Clay's string implementation
11. **Chapter 11: Type Casting** - Implicit/explicit conversion, const, volatile
12. **Chapter 12: Storage Classes** - auto, static, extern, scope, lifetime
13. **Chapter 13: Recursion** - Base cases, tail recursion, tree traversal
### Part 2: Advanced Topics (Separate Files)
#### **Chapter 14: Bit Manipulation** 📄
**File: `docs/14_bit_manipulation.md`**
- Bitwise operators (&, |, ^, ~, <<, >>)
- Bit flags and masks
- Set/clear/toggle/check bits
- Counting set bits
- Power of 2 operations
- Practical applications in Clay
- Performance optimizations
#### **Chapter 15: Preprocessor and Macros**
**File: `LEARNING_C_WITH_CLAY.md`** (Chapter 15)
- #define and #include
- Conditional compilation (#ifdef, #ifndef)
- Header guards
- Function-like macros
- Stringification and token pasting
- Predefined macros
#### **Chapter 16: Advanced Macros**
**File: `LEARNING_C_WITH_CLAY.md`** (Chapter 16)
- Variadic macros
- X-Macros pattern
- _Generic for type selection
- Compound literals
- For-loop macro trick (Clay's CLAY() macro)
- Macro debugging
#### **Chapter 17: Memory Management**
**File: `LEARNING_C_WITH_CLAY.md`** (Chapter 17)
- Stack vs heap
- malloc, calloc, realloc, free
- Memory errors and debugging
- Arena allocators (Clay's approach)
- Memory pools
- Alignment
#### **Chapter 18: Header Files**
**File: `LEARNING_C_WITH_CLAY.md`** (Chapter 18)
- Header vs source files
- Header guards and #pragma once
- Single-header library pattern (Clay)
- Forward declarations
- Opaque pointers
- Platform-specific code
#### **Chapter 19: Enums and Unions**
**File: `LEARNING_C_WITH_CLAY.md`** (Chapter 19)
- Enum basics and typedef
- Bit flags with enums
- Unions for memory efficiency
- Tagged unions
- Anonymous structs/unions
#### **Chapter 20: Function Pointers**
**File: `LEARNING_C_WITH_CLAY.md`** (Chapter 20)
- Function pointer basics
- Typedef for cleaner syntax
- Callbacks (Clay's measurement callbacks)
- Function pointer arrays
- User data pattern
#### **Chapter 21: Standard Library Basics** 📄
**File: `docs/21_standard_library.md`**
- stdio.h - printf, scanf, file operations
- stdlib.h - malloc, atoi, rand, exit
- string.h - strlen, strcpy, strcmp
- math.h - pow, sqrt, trigonometry
- ctype.h - character testing
- time.h - time operations
- Clay's zero-dependency approach
#### **Chapter 22: File I/O** 📄
**File: `docs/22_file_io.md`**
- Opening and closing files
- File modes (read, write, append, binary)
- fprintf, fscanf, fgets, fputs
- fread, fwrite for binary data
- File position (ftell, fseek, rewind)
- Error handling
- Configuration files for Clay apps
- Binary file formats
#### **Chapter 23: Command-Line Arguments** 📄
**File: `docs/23_command_line_arguments.md`**
- argc and argv basics
- Parsing arguments
- Command-line flags
- getopt for option parsing
- Subcommands (git-style)
- Configuration priority
- Clay application with arguments
- Interactive vs batch mode
#### **Chapter 24: Building Complete Programs**
**File: `LEARNING_C_WITH_CLAY.md`** (Chapter 24)
- Complete Clay example
- Compiling with gcc/clang
- Makefiles for automation
- Multi-file projects
- Common C patterns
- Best practices
---
## 🎯 Learning Path
### Beginner (Chapters 1-9)
Start here if you're new to C. Learn the fundamentals:
- Basic syntax and data types
- Control structures and loops
- Functions and pointers
- Structs and arrays
**Estimated time:** 2-3 weeks
### Intermediate (Chapters 10-17)
Build on fundamentals with more advanced topics:
- String manipulation
- Type casting and storage classes
- Recursion and bit manipulation
- Preprocessor and macros
- Memory management
**Estimated time:** 3-4 weeks
### Advanced (Chapters 18-24)
Master professional C development:
- Project organization
- Advanced data structures
- Function pointers and callbacks
- File I/O and system interaction
- Complete application development
**Estimated time:** 2-3 weeks
---
## 🚀 Quick Start
1. **Read the main guide** (`LEARNING_C_WITH_CLAY.md`) from Chapter 1
2. **Follow along** by writing the code examples
3. **Study Clay's implementation** in `clay.h` for real-world patterns
4. **Complete practice exercises** at the end of each chapter
5. **Refer to specialized topics** in the `docs/` folder as needed
---
## 💡 Why Learn C with Clay?
### Clay Library Features
- **Single-header**: Entire library in one file
- **Zero dependencies**: No standard library required
- **High performance**: Microsecond layout calculations
- **Professional code**: Production-ready patterns
- **Well-documented**: Clear, readable implementation
### What Clay Teaches You
- ✅ Arena allocators for memory management
- ✅ Macro DSL design
- ✅ Single-header library pattern
- ✅ API design principles
- ✅ Zero-dependency C programming
- ✅ Performance optimization techniques
- ✅ Portable C code practices
---
## 📁 File Structure
```
clay/
├── LEARNING_C_WITH_CLAY.md # Main tutorial (Chapters 1-13, 15-20, 24)
├── clay.h # The Clay library (reference)
├── docs/
│ ├── README_C_TUTORIALS.md # This index file
│ ├── 14_bit_manipulation.md # Chapter 14: Bit operations
│ ├── 21_standard_library.md # Chapter 21: stdlib overview
│ ├── 22_file_io.md # Chapter 22: File operations
│ └── 23_command_line_arguments.md # Chapter 23: argc/argv
└── examples/ # Clay examples to study
```
---
## 🔧 Prerequisites
- A C compiler (gcc, clang, or MSVC)
- Text editor or IDE
- Basic command-line knowledge
- Curiosity and patience!
### Setting Up
**Linux/Mac:**
```bash
gcc --version # Check compiler
```
**Windows:**
- Install MinGW or Visual Studio
- Or use WSL (Windows Subsystem for Linux)
---
## 📝 How to Use This Guide
### Reading the Main Tutorial
```bash
# View in terminal
less LEARNING_C_WITH_CLAY.md
# Or open in your favorite markdown viewer
```
### Compiling Examples
```c
// example.c
#include <stdio.h>
int main(void) {
printf("Hello, C!\n");
return 0;
}
```
```bash
# Compile
gcc -o example example.c
# Run
./example
```
### Studying Clay
```c
// your_program.c
#define CLAY_IMPLEMENTATION
#include "clay.h"
int main(void) {
// Your Clay UI code here
return 0;
}
```
---
## 🎓 Practice Exercises
Each chapter includes practice exercises. Try them all!
**Example exercises:**
- Chapter 5: Build a number guessing game
- Chapter 7: Implement your own string functions
- Chapter 14: Create a permission system with bit flags
- Chapter 22: Build a CSV parser
- Chapter 24: Create a complete Clay application
---
## 📚 Additional Resources
### Clay Resources
- **Clay Website**: https://nicbarker.com/clay
- **Clay GitHub**: https://github.com/nicbarker/clay
- **Examples**: See `clay/examples/` directory
### C Programming Resources
- **C Reference**: https://en.cppreference.com/w/c
- **Book**: "The C Programming Language" by K&R
- **Book**: "Modern C" by Jens Gustedt
- **Online**: C tutorials on YouTube, freeCodeCamp
### Tools
- **Compiler Explorer**: https://godbolt.org
- **Valgrind**: Memory leak detection
- **GDB**: Debugging
- **Clang-format**: Code formatting
---
## 🤝 Contributing
Found an error? Have a suggestion? Contributions welcome!
---
## ⭐ Features of This Guide
- ✅ **Progressive learning** - Start simple, build complexity
- ✅ **Real-world examples** - Every concept shown in Clay
- ✅ **Complete coverage** - All C topics from basics to advanced
- ✅ **Practical focus** - Build real programs, not just theory
- ✅ **Professional patterns** - Learn industry best practices
- ✅ **Zero to hero** - From "Hello World" to complex applications
---
## 🎯 Learning Goals
After completing this guide, you will be able to:
1. ✅ Write efficient, well-structured C programs
2. ✅ Understand memory management and pointers
3. ✅ Use advanced C features (macros, unions, bit manipulation)
4. ✅ Organize multi-file C projects
5. ✅ Read and understand professional C code (like Clay)
6. ✅ Debug and optimize C programs
7. ✅ Build complete applications with file I/O and CLI
8. ✅ Apply C knowledge to systems programming
---
## 📖 Chapter Dependencies
```
Chapter 1-2 (Basics)
↓
Chapter 3-5 (Control Flow)
↓
Chapter 6 (Functions)
↓
Chapter 7 (Pointers) ←─────────┐
↓ │
Chapter 8 (Structs) │
↓ │
Chapter 9 (Arrays) ────────────┘
↓
Chapter 10 (Strings)
↓
Chapter 11-12 (Advanced Types)
↓
Chapter 13 (Recursion)
├─→ Chapter 14 (Bit Manipulation)
├─→ Chapter 15-16 (Macros)
├─→ Chapter 17 (Memory)
├─→ Chapter 18 (Organization)
├─→ Chapter 19 (Enums/Unions)
├─→ Chapter 20 (Function Pointers)
├─→ Chapter 21 (Standard Library)
├─→ Chapter 22 (File I/O)
└─→ Chapter 23 (Command Line)
↓
Chapter 24 (Complete Programs)
```
---
## 🏆 Completion Checklist
Track your progress:
- [ ] Chapter 1-5: Fundamentals
- [ ] Chapter 6-9: Functions, Pointers, Structs, Arrays
- [ ] Chapter 10-13: Strings, Casting, Storage, Recursion
- [ ] Chapter 14: Bit Manipulation
- [ ] Chapter 15-16: Preprocessor and Macros
- [ ] Chapter 17: Memory Management
- [ ] Chapter 18: Project Organization
- [ ] Chapter 19: Enums and Unions
- [ ] Chapter 20: Function Pointers
- [ ] Chapter 21: Standard Library
- [ ] Chapter 22: File I/O
- [ ] Chapter 23: Command-Line Arguments
- [ ] Chapter 24: Building Complete Programs
- [ ] Built a complete Clay application
- [ ] Read and understood clay.h
---
## 💬 Tips for Success
1. **Type every example** - Don't just read, code!
2. **Experiment** - Modify examples to see what happens
3. **Read clay.h** - Study professional code
4. **Complete exercises** - Practice makes perfect
5. **Debug your errors** - Learn from mistakes
6. **Build projects** - Apply what you learn
7. **Ask questions** - Join C programming communities
8. **Be patient** - C takes time to master
---
## 🚀 Next Steps After This Guide
1. **Build projects** - Create your own applications
2. **Study data structures** - Implement lists, trees, hash tables
3. **Learn algorithms** - Sorting, searching, graph algorithms
4. **Explore systems programming** - OS concepts, networking
5. **Contribute to open source** - Read and improve real projects
6. **Specialize** - Embedded systems, game dev, or systems programming
---
## 📜 License
This educational content is provided for learning purposes.
Clay library: MIT License - see Clay repository for details.
---
## 🎉 Happy Coding!
Welcome to the world of C programming! With dedication and practice, you'll master one of the most powerful and influential programming languages ever created.
**Remember:** Every expert was once a beginner. Start with Chapter 1 and work your way through. You've got this! 🚀
---
*"C is quirky, flawed, and an enormous success." - Dennis Ritchie*