QUESTION 11 · Function Communication

Does changing an integer parameter change the caller’s variable?

2 marks

Answer

No. C passes its value into a separate parameter object.

The parameter can be changed without changing the original integer variable.
To request a change to a caller’s object, a suitable pointer can be passed.

Explain call by value in C with an example.

5 marks

Answer in brief

C uses pass by value: each parameter receives a value supplied by the corresponding argument. An ordinary integer parameter is a separate object from the caller’s integer variable.

Working

The caller evaluates the argument expression.
The resulting value is used for the parameter according to the declared type.
The function works with its parameter object. Assigning a new value to that parameter does not assign to the caller’s variable.

Example trace

main starts with number = 10 and calls change(number). The parameter n receives 10. Inside change, n = 25 changes only n, so the first line prints 25. After the function returns, number in main still contains 10. This shows the difference between a copied value and the original object.

Advantages

A function can use and update a working parameter without unintentionally replacing the caller’s ordinary value. This helps keep calculations separate. For example, a digit-processing function can repeatedly divide its local copy while the original input remains available to main.

Pointer clarification

Passing an address does not change C into pass by reference. The address is a pointer value, and that value is copied into a pointer parameter. The function can use the copied pointer to access the same caller-owned object. Changing the pointer parameter itself is different from changing the object to which it points.

Complexity

The fixed-size integer example uses constant work and a fixed number of objects, so time and extra space are O(1). The copying cost of an argument depends on its type; do not assume every possible argument is a single small integer.

C program and output

Download .c Open compiler

/* CodeBhavya | PPS AR25 | Learning example */
#include <stdio.h>
void change(int n)
{
    n = 25;
    printf("Inside = %d\n", n);
}
int main(void)
{
    int number = 10;
    change(number);
    printf("Outside = %d\n", number);
    return 0;
}

Sample input and output

This example uses values already written in the program.

Output

Inside = 25
Outside = 10