Function Arguments and Call by Value in C Practice Questions with Solutions

Introduction

Function arguments allow you to send data from one part of a C program to a function. In C, ordinary function arguments are passed using call by value, which means the function receives a copy of the original value. Changes made to the parameter inside the function do not change the original variable. In this chapter, you will practice function arguments and call by value through 10 examples covering calculations, comparisons, swapping, conditions, and practical programming situations. Function Arguments and Call by Value in C practice questions with solutions to help you understand the concepts.

Q1. Pass One Number to a Function

Problem Statement

Write a C program that passes a number to a function and prints the number inside the function.

C Program

#include <stdio.h>

void displayNumber(int number)
{
    printf("Number = %d", number);
}

int main()
{
    int n = 25;

    displayNumber(n);

    return 0;
}

Sample Output

Number = 25

Explanation

The variable:

int n = 25;

is passed to:

displayNumber(n);

The function receives the value in its parameter:

void displayNumber(int number)

So:

n       = 25
number  = 25

The function then prints the value.

Concepts Covered

Function argument
Function parameter
Function call
int parameter

Q2. Pass Two Numbers to a Function

Problem Statement

Write a C program that passes two numbers to a function and prints their sum.

C Program

#include <stdio.h>

void add(int a, int b)
{
    int sum;

    sum = a + b;

    printf("Sum = %d", sum);
}

int main()
{
    int x = 15;
    int y = 25;

    add(x, y);

    return 0;
}

Sample Output

Sum = 40

Explanation

The function has two parameters:

void add(int a, int b)

The call is:

add(x, y);

At the time of the call:

x → 15 → a
y → 25 → b

The function calculates:

15 + 25 = 40

Concepts Covered

Multiple arguments
Multiple parameters
Function call
Addition

Q3. Find the Largest of Two Numbers

Problem Statement

Write a C program that passes two numbers to a function and finds the larger number.

C Program

#include <stdio.h>

void findLargest(int a, int b)
{
    if (a > b)
    {
        printf("%d is larger.", a);
    }
    else
    {
        printf("%d is larger.", b);
    }
}

int main()
{
    int x = 45;
    int y = 30;

    findLargest(x, y);

    return 0;
}

Sample Output

45 is larger.

Explanation

The values of x and y are passed to the function.

findLargest(x, y);

The function compares:

if (a > b)

Since:

45 > 30

the program prints 45.

Concepts Covered

Function arguments
Parameters
if-else
Relational operator

Q4. Demonstrate Call by Value

Problem Statement

Write a C program to demonstrate that changing a function parameter does not change the original variable.

C Program

#include <stdio.h>

void changeValue(int number)
{
    number = 100;

    printf("Value inside function = %d\n", number);
}

int main()
{
    int number = 50;

    printf("Before function call = %d\n", number);

    changeValue(number);

    printf("After function call = %d", number);

    return 0;
}

Sample Output

Before function call = 50
Value inside function = 100
After function call = 50

Explanation

Initially:

number = 50

We call:

changeValue(number);

The function receives a copy of 50.

Inside the function:

number = 100;

changes the function’s local parameter.

It does not change the original variable in main().

Therefore:

Inside function → 100
Original variable → 50

This is the basic idea of call by value in C.

Concepts Covered

Call by value
Function parameter
Local copy
Original variable

Q5. Try to Change Two Variables Using Call by Value

Problem Statement

Write a C program that attempts to change two variables inside a function and observe whether the original variables change.

C Program

#include <stdio.h>

void changeValues(int a, int b)
{
    a = 100;
    b = 200;

    printf("Inside function:\n");
    printf("a = %d\n", a);
    printf("b = %d\n", b);
}

int main()
{
    int x = 10;
    int y = 20;

    printf("Before function call:\n");
    printf("x = %d\n", x);
    printf("y = %d\n", y);

    changeValues(x, y);

    printf("\nAfter function call:\n");
    printf("x = %d\n", x);
    printf("y = %d\n", y);

    return 0;
}

Sample Output

Before function call:
x = 10
y = 20

Inside function:
a = 100
b = 200

After function call:
x = 10
y = 20

Explanation

The function receives copies:

x → copy → a
y → copy → b

Inside the function:

a = 100;
b = 200;

only changes the copies.

The original values remain:

x = 10
y = 20

This is why ordinary C function arguments use call by value.

Concepts Covered

Multiple arguments
Call by value
Original variables
Local parameters

Q6. Swap Two Variables Using Call by Value

Problem Statement

Write a C program that tries to swap two numbers inside a function using ordinary function arguments.

Observe whether the original values are swapped.

C Program

#include <stdio.h>

void swap(int a, int b)
{
    int temp;

    temp = a;
    a = b;
    b = temp;

    printf("Inside function:\n");
    printf("a = %d\n", a);
    printf("b = %d\n", b);
}

int main()
{
    int x = 10;
    int y = 20;

    printf("Before function call:\n");
    printf("x = %d\n", x);
    printf("y = %d\n", y);

    swap(x, y);

    printf("\nAfter function call:\n");
    printf("x = %d\n", x);
    printf("y = %d\n", y);

    return 0;
}

Sample Output

Before function call:
x = 10
y = 20

Inside function:
a = 20
b = 10

After function call:
x = 10
y = 20

Explanation

Inside the function, the values are successfully swapped:

a = 20
b = 10

But a and b are copies of x and y.

Therefore, the original variables remain:

x = 10
y = 20

This is an important example of call by value.

To actually modify the original variables, pointers are used. That topic will be covered later.

Concepts Covered

Call by value
Swapping
Temporary variable
Function arguments

Q7. Calculate Area Using Function Arguments

Problem Statement

Write a C program that passes the length and width of a rectangle to a function and calculates its area.

Formula:

Area = Length × Width

C Program

#include <stdio.h>

void rectangleArea(float length, float width)
{
    float area;

    area = length * width;

    printf("Area = %.2f", area);
}

int main()
{
    float length = 10.5;
    float width = 5.0;

    rectangleArea(length, width);

    return 0;
}

Sample Output

Area = 52.50

Explanation

Two values are passed:

rectangleArea(length, width);

The function receives them as:

float length
float width

Then:

area = length * width;

calculates:

10.5 × 5.0 = 52.5

Concepts Covered

Function arguments
float parameters
Multiplication
Area calculation

Q8. Check Whether a Number Is Even or Odd

Problem Statement

Create a function that accepts a number and checks whether it is even or odd.

C Program

#include <stdio.h>

void checkEvenOdd(int number)
{
    if (number % 2 == 0)
    {
        printf("%d is even.", number);
    }
    else
    {
        printf("%d is odd.", number);
    }
}

int main()
{
    int number;

    printf("Enter a number: ");
    scanf("%d", &number);

    checkEvenOdd(number);

    return 0;
}

Sample Output

Enter a number: 28
28 is even.

Explanation

The user enters a number.

For example:

number = 28

The value is passed to:

checkEvenOdd(number);

The function checks:

number % 2 == 0

Because:

28 % 2 = 0

the number is even.

Concepts Covered

Function arguments
User input
Modulus operator
if-else

Q9. Calculate Simple Interest Using Function Arguments

Problem Statement

Create a function that accepts principal, rate, and time and calculates simple interest.

Formula:

Simple Interest = (P × R × T) / 100

C Program

#include <stdio.h>

void simpleInterest(float principal, float rate, float time)
{
    float interest;

    interest = (principal * rate * time) / 100;

    printf("Simple Interest = %.2f", interest);
}

int main()
{
    float principal = 10000;
    float rate = 5;
    float time = 2;

    simpleInterest(principal, rate, time);

    return 0;
}

Sample Output

Simple Interest = 1000.00

Explanation

Three arguments are passed:

simpleInterest(principal, rate, time);

Their values are:

Principal = 10000
Rate      = 5
Time      = 2

The function calculates:

(10000 × 5 × 2) / 100
= 1000

Concepts Covered

Multiple function arguments
float
Mathematical formula
Function parameters

Q10. Perform Multiple Calculations Using Call by Value

Problem Statement

Create separate functions to calculate the sum, difference, product, and average of two numbers. Pass the numbers to each function using ordinary arguments.

C Program

#include <stdio.h>

void sum(int a, int b)
{
    printf("Sum = %d\n", a + b);
}

void difference(int a, int b)
{
    printf("Difference = %d\n", a - b);
}

void product(int a, int b)
{
    printf("Product = %d\n", a * b);
}

void average(int a, int b)
{
    float result;

    result = (a + b) / 2.0;

    printf("Average = %.2f\n", result);
}

int main()
{
    int x = 20;
    int y = 10;

    sum(x, y);
    difference(x, y);
    product(x, y);
    average(x, y);

    return 0;
}

Sample Output

Sum = 30
Difference = 10
Product = 200
Average = 15.00

Explanation

The same two variables are passed to four different functions:

sum(x, y);
difference(x, y);
product(x, y);
average(x, y);

Each function receives its own copies of the values.

The original x and y remain unchanged.

This demonstrates how function arguments allow the same data to be used by different functions.

Concepts Covered

Multiple functions
Multiple arguments
Call by value
Arithmetic operations
Reusable functions

Key Takeaways

Function arguments are values passed to a function.
Function parameters are variables that receive those values.
In ordinary C function calls, arguments are passed by value.
Call by value means the function receives a copy of each argument’s value.
Changing a parameter inside the function does not change the original variable.
Multiple arguments can be passed to a function.
Different data types such as int and float can be used as parameters.
Call by value is useful when a function only needs to work with copies of the data.
A simple swap() function using ordinary parameters cannot change the caller’s original variables.
Pointers allow functions to work with the original objects and will be covered later.
Understanding arguments and parameters is essential before learning return values and pointers.
Functions can receive the same variables in multiple function calls without changing them.

FAQs

1. What are function arguments in C?

Function arguments are the actual values passed to a function when it is called.

Example:

add(10, 20);

Here, 10 and 20 are arguments.

2. What are function parameters in C?

Parameters are variables declared in a function definition that receive the arguments.

Example:

void add(int a, int b)

Here, a and b are parameters.

3. What is call by value in C?

Call by value means the function receives a copy of the value passed by the caller. Changes to the parameter do not change the original variable.

4. Does C support call by value?

Yes. C passes ordinary function arguments by value.

For example:

void change(int x)
{
    x = 100;
}

Changing x does not change the caller’s original variable.

5. Can a function have multiple arguments?

Yes. A function can accept multiple parameters.

Example:

void add(int a, int b, int c)
{
    printf("%d", a + b + c);
}

It can be called as:

add(10, 20, 30);

6. Why does swapping two variables not work with ordinary function arguments?

Because the function receives copies of the values.

Changing the copies does not change the original variables in the calling function.

Pointers can be used when you need a function to modify the original variables.

7. What is the difference between an argument and a parameter?

An argument is the actual value passed during a function call.

A parameter is the variable that receives that value inside the function.

Example:

add(10, 20);

Here 10 and 20 are arguments.

void add(int a, int b)

Here a and b are parameters.

Written by Shubhranshu Shekhar, who has trained 20000+ students in coding.

Rishabh Kumar

Introduction

Q1. Pass One Number to a Function

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q2. Pass Two Numbers to a Function

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q3. Find the Largest of Two Numbers

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q4. Demonstrate Call by Value

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q5. Try to Change Two Variables Using Call by Value

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q6. Swap Two Variables Using Call by Value

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q7. Calculate Area Using Function Arguments

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q8. Check Whether a Number Is Even or Odd

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q9. Calculate Simple Interest Using Function Arguments

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q10. Perform Multiple Calculations Using Call by Value

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Key Takeaways

FAQs

1. What are function arguments in C?

2. What are function parameters in C?

3. What is call by value in C?

4. Does C support call by value?

5. Can a function have multiple arguments?

6. Why does swapping two variables not work with ordinary function arguments?

7. What is the difference between an argument and a parameter?

Related Posts