In this tutorial, you will learn in-depth about C string library function memset() with explanation and explicit example.

memset() is built in standard string function that is defined in string header library string.h. Therefore, to use this function we should include string.h.

#include<string.h>

Function prototype of C string library function memset()

void *memset( const void *str, int ch, size_t n );

where,

str = pointer to the object or block of memory that needs to be set

ch = value that is copied, converted to unsigned char

n = number of bytes to be set

This function copies ch (represented as unsigned char) into the first n characters of the object or memory block pointed by str.

memset() returns a pointer to the block of memory.

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C program to demonstrate the function of string library function memset()

/*Use of string library function memset*/

#include<stdio.h>
#include<string.h>

int main()
{
   //initializing character array
   char str[ 30 ] = "Learn C from trytoprogram.com";

   //displaying str
   printf("str = %s\n\n", str);

   printf("str after memset( str, '*', 5 ) : %s\n", memset(str, '*', 5));

   return 0;
}

Output

Explanation

In the above program, we have copied '*' into first 5 characters of array str.