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      • C Functions

      Overview

      Functions are the building blocks of C programs. They allow code reuse, modularization, and better organization.

      Function Declaration and Definition

      Function Declaration (Prototype)

      return_type function_name(parameter_list);

      Function Definition

      return_type function_name(parameter_list) {
    // function body
    return value;
}

      Example Functions

      Simple Function

      #include <stdio.h>

// Function declaration
int add(int a, int b);

int main() {
    int result = add(5, 3);
    printf("Result: %d\n", result);  // Output: Result: 8
    return 0;
}

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

      Function with Multiple Parameters

      float calculate_average(int a, int b, int c) {
    return (float)(a + b + c) / 3;
}

      Function with No Parameters

      void print_hello() {
    printf("Hello, World!\n");
}

      Function with No Return Value

      void print_number(int num) {
    printf("Number: %d\n", num);
}

      Function Parameters

      Pass by Value

      void modify_value(int x) {
    x = 100;  // Only modifies local copy
}

      Pass by Reference (using pointers)

      void modify_value(int *x) {
    *x = 100;  // Modifies original value
}

      Best Practices

      1. Use descriptive function names
      2. Keep functions small and focused
      3. Use prototypes for better code organization
      4. Document functions with comments
      5. Handle edge cases properly