Page 73 - DCAP407_DATA_STRUCTURE

Data Structure

Advantages of Pass by Value or Call by Value
1. In Pass by value, expressions are passed as arguments instead of passing the values
or variables as arguments.
2. This protects the values of the actual variables from getting altered by the called
function.

Disadvantages of Pass by Value or Call by Value
1. Pass by value technique will not allow the information to be sent back to the calling
portion of the program.

2. It allows only one-way transfer of information i.e., from the calling function to the
called function.

Write a C program to swap two numbers using pointers.

Pass by Reference or Call by Reference

When an address is passed to a function, the parameters receiving the address will have to be pointers.
The process of calling a function by using pointers to pass the address of the variable is called pass by
reference or call by reference. The function called by reference changes the values of the variable used in
the call.

#include<stdio.h>
void num(int *x, int *y)
{
*x = 100;
*y = 200;
}
void main()
{
int m, n;
m = 10;
n = 20;
num(&m, &n);
printf( “ m = %d and n= %d”, m, n);
getch();
}

Output:
m = 100 and n = 200
There is a difference in output between the above two examples. The function
num() is called again. The output will be 100 and 200. Here, instead of passing the
values of actual parameters, the addresses of actual parameters, i.e., &m and &n are
passed. The addresses are copied into formal parameters. Since the formal
parameters contain the addresses, they are considered as pointers. The sequences of
steps are as follows:
1. Execution of the calling process i.e., the main function will start. Since, the
variables m and n are defined within the function, memory is allocated for
these variables during run-time and initialized with junk values ‘?’. Assume
that the addresses of the variables are 1004 and 1008.

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