Following coding conventions improves code consistency within a project.

// C coding conventions example:
// 1. Use meaningful variable and function names
// 2. Indent code with 4 spaces
// 3. Add comments to explain complex logic
// 4. Declare variables at the beginning of the block
// 5. Use camelCase for variable and function names
// 6. Use UPPER_CASE for constants
// 7. Keep lines under 80 characters

Writing clean and well-organized code enhances readability and maintainability.

// Bad coding style
int f(int x){int i=0;for(;i<x;++i)printf("%d ",i);return i;}

// Improved coding style
int print_numbers(int limit) {
    for (int i = 0; i < limit; ++i) {
        printf("%d ", i);
    }
    return limit;
}

Code optimization aims to improve the performance and efficiency of the program.

#include <stdio.h>

int main() {
    int x = 10;
    if (x == 10) {
        printf("x is 10\n");
    }
    return 0;
}

Debugging helps identify and fix errors in the code.

#include <stdio.h>

int main() {
    int x = 10, y = 0;
    int result = x / y; // Division by zero
    printf("Result: %d\n", result); // Causes a runtime error (division by zero)
    return 0;
}

To use functions from external libraries, you need to link them during the compilation process.

// Compile with math library
// gcc main.c -lm -o main
#include <stdio.h>
#include <math.h>

int main() {
    double result = pow(2, 3);
    printf("2^3 = %.2f\n", result); // Output: 2^3 = 8.00
    return 0;
}

Header files contain function prototypes and other declarations.

// math_operations.h
#ifndef MATH_OPERATIONS_H
#define MATH_OPERATIONS_H

int add(int a, int b);
int subtract(int a, int b);

#endif

// math_operations.c
#include "math_operations.h"

int add(int a, int b) {
    return a + b;
}

int subtract(int a, int b) {
    return a - b;
}

// main.c
#include <stdio.h>
#include "math_operations.h"

int main() {
    int result = add(10, 5);
    printf("Addition: %d\n", result); // Output: 15

    result = subtract(10, 5);
    printf("Subtraction: %d\n", result); // Output: 5
    return 0;
}

The C standard library provides many built-in functions to perform various operations.

#include <stdio.h>
#include <string.h>

int main() {
    // String manipulation functions
    char str1[] = "Hello";
    char str2[10];
    strcpy(str2, str1); // Copy str1 to str2
    printf("%s\n", str2); // Output: Hello

    // Mathematical functions
    double result = sqrt(25);
    printf("Square root of 25: %.2f\n", result); // Output: 5.00
    return 0;
}

Error handling involves dealing with unexpected or exceptional situations.

#include <stdio.h>
#include <errno.h>
#include <string.h>

int main() {
    FILE *file = fopen("non_existent_file.txt", "r");
    if (file == NULL) {
        printf("Error: %s\n", strerror(errno));
    }
    return 0;
}

Command-line arguments allow passing arguments to a C program when executing it from the terminal.

int main(int argc, char *argv[]) {
    if (argc > 1) {
        printf("First argument: %s\n", argv[1]);
    }
    return 0;
}

Bit manipulation involves performing operations at the bit level.

// Setting a bit using bitwise OR (|)
int num = 5; // Binary: 0101
int mask = 1; // Binary: 0001
int result = num | mask; // Binary: 0101 | 0001 = 0101
printf("%d\n", result); // Output: 5