How to pass arguments to function in C?

Passing Arguments to Functions in C

In the C programming language, functions are used to encapsulate and reuse blocks of code. When you call a function, you can pass arguments to it, which are values that the function can use to perform its task. Passing arguments to functions is a fundamental concept in C programming, and it allows you to create more flexible and powerful programs.

Passing Arguments by Value

The most common way to pass arguments to a function in C is by value. When you pass an argument by value, the function receives a copy of the argument's value, and any changes made to the argument within the function do not affect the original value outside the function.

Here's an example:

#include <stdio.h>

void increment(int x) {
    x++;
    printf("Inside the function, x = %d\n", x);
}

int main() {
    int num = 5;
    printf("Before the function call, num = %d\n", num);
    increment(num);
    printf("After the function call, num = %d\n", num);
    return 0;
}

Output:

Before the function call, num = 5
Inside the function, x = 6
After the function call, num = 5

In this example, the increment function receives the value of the num variable as an argument. Inside the function, the value of x is incremented, but this change does not affect the original value of num outside the function.

Passing Arguments by Reference

In addition to passing arguments by value, C also allows you to pass arguments by reference. When you pass an argument by reference, the function receives the memory address of the argument, which allows the function to modify the original value.

To pass an argument by reference, you need to use a pointer. Here's an example:

#include <stdio.h>

void increment(int *x) {
    (*x)++;
    printf("Inside the function, *x = %d\n", *x);
}

int main() {
    int num = 5;
    printf("Before the function call, num = %d\n", num);
    increment(&num);
    printf("After the function call, num = %d\n", num);
    return 0;
}

Output:

Before the function call, num = 5
Inside the function, *x = 6
After the function call, num = 6

In this example, the increment function takes a pointer to an integer as its argument. Inside the function, the value pointed to by x is incremented, and this change affects the original value of num outside the function.

Passing Arrays as Arguments

When you pass an array as an argument to a function, you can either pass the entire array or pass a pointer to the first element of the array. Here's an example:

#include <stdio.h>

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

int main() {
    int numbers[] = {1, 2, 3, 4, 5};
    int size = sizeof(numbers) / sizeof(numbers[0]);
    printArray(numbers, size);
    return 0;
}

Output:

1 2 3 4 5

In this example, the printArray function takes an array of integers and its size as arguments. The function then prints all the elements of the array.

Passing Structures as Arguments

C also allows you to pass structures as arguments to functions. You can pass the entire structure or a pointer to the structure. Here's an example:

#include <stdio.h>

typedef struct {
    int age;
    float height;
} Person;

void printPerson(Person p) {
    printf("Age: %d, Height: %.2f\n", p.age, p.height);
}

void modifyPerson(Person *p) {
    p->age = 30;
    p->height = 1.75;
}

int main() {
    Person person = {25, 1.68};
    printPerson(person);
    modifyPerson(&person);
    printPerson(person);
    return 0;
}

Output:

Age: 25, Height: 1.68
Age: 30, Height: 1.75

In this example, the printPerson function takes a Person structure as an argument and prints its age and height. The modifyPerson function takes a pointer to a Person structure as an argument and modifies the age and height of the person.

By understanding how to pass arguments to functions in C, you can write more flexible and powerful programs that can handle a wide range of input and perform complex tasks.