Function Parameters

Types of Parameters

void func(int x) {
    x = 10; // Original unchanged
}

void func(int *x) {
    *x = 10; // Original changed
}

void func(int arr[], int size) {
    // Process array
}

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

🔹 Basic Parameter Example

Simple functions with single parameters demonstrate how data passes into functions and calculations occur. Parameters receive values from function calls, enabling functions to operate on different data each time. The function processes the parameter value, performs calculations, and returns results. Understanding parameter passing is fundamental to functional programming, enabling code reuse and modularity. Practice writing functions with various parameter types to master data passing mechanics.

#include <stdio.h>

void printSquare(int number) {
    int result = number * number;
    printf("Square of %d is %d\n", number, result);
}

int main() {
    printSquare(5);
    printSquare(8);
    printSquare(12);
    return 0;
}

🔹 Multiple Parameters

Functions can accept multiple parameters enabling complex operations on different data values simultaneously. Each parameter has its own data type and name, allowing functions to work with various inputs in coordinated ways. Parameters pass from left to right in function calls, matching the function definition order. This flexibility enables designing versatile functions handling different combinations of inputs and producing diverse outputs based on multiple inputs simultaneously.

#include <stdio.h>

float calculateArea(float length, float width) {
    return length * width;
}

void displayInfo(char name[], int age, float height) {
    printf("Name: %s\n", name);
    printf("Age: %d years\n", age);
    printf("Height: %.1f cm\n", height);
}

int main() {
    float area = calculateArea(10.5, 8.2);
    printf("Area: %.2f\n\n", area);
    
    displayInfo("John", 25, 175.5);
    return 0;
}

🔹 Pass by Value vs Pass by Reference

Understanding pass-by-value and pass-by-reference is critical for controlling how function parameters behave and affect original variables. Pass-by-value creates copies of arguments, preventing function modifications from affecting original variables, ensuring safety and predictability. Pass-by-reference using pointers allows functions to modify original variables, enabling functions to produce multiple outputs or modify caller data directly. Choose the appropriate passing mechanism based on whether functions should modify original data.

🔸 Pass by Value (Copy)

#include <stdio.h>

void changeValue(int x) {
    x = 100;  // Only changes the copy
    printf("Inside function: %d\n", x);
}

int main() {
    int num = 50;
    printf("Before function: %d\n", num);
    changeValue(num);
    printf("After function: %d\n", num);  // Original unchanged
    return 0;
}

🔸 Pass by Reference (Pointer)

#include <stdio.h>

void changeValue(int *x) {
    *x = 100;  // Changes the original
    printf("Inside function: %d\n", *x);
}

int main() {
    int num = 50;
    printf("Before function: %d\n", num);
    changeValue(#);  // Pass address
    printf("After function: %d\n", num);  // Original changed
    return 0;
}

🔹 Array as Parameter

Passing arrays to functions enables processing collections of data within functions, making code modular and reusable. Array parameters pass by reference by default, allowing functions to modify array contents. Include array size parameters to enable functions to process entire arrays safely. Use this pattern for functions performing calculations on collections, filtering data, or transforming arrays while maintaining array contents outside the function.

#include <stdio.h>

void printArray(int arr[], int size) {
    printf("Array elements: ");
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

int findSum(int numbers[], int count) {
    int sum = 0;
    for (int i = 0; i < count; i++) {
        sum += numbers[i];
    }
    return sum;
}

int main() {
    int myArray[] = {10, 20, 30, 40, 50};
    int size = 5;
    
    printArray(myArray, size);
    int total = findSum(myArray, size);
    printf("Sum: %d\n", total);
    return 0;
}