c program to compare two strings

This c program compares two strings using strcmp, without strcmp and using pointers. For comparing strings without using library function see another code below.

C program to compare two strings using strcmp

#include<stdio.h>
#include<string.h>
 
main()
{
   char a[100], b[100];
 
   printf("Enter the first string\n");
   gets(a);
 
   printf("Enter the second string\n");
   gets(b);
 
   if( strcmp(a,b) == 0 )
      printf("Entered strings are equal.\n");
   else
      printf("Entered strings are not equal.\n");
 
   return 0;
}

C program to compare two strings without using strcmp

Here we create our own function to compare strings.

int compare(char a[], char b[])
{
   int c = 0;
 
   while( a[c] == b[c] )
   {
      if( a[c] == '\0' || b[c] == '\0' )
         break;
      c++;
   }
   if( a[c] == '\0' && b[c] == '\0' )
      return 0;
   else
      return -1;
}

C program to compare two strings using pointers

In this method we will make our own function to perform string comparison, we will use character pointers in our function to manipulate string.

#include<stdio.h>
 
int compare_string(char*, char*);
 
main()
{
    char first[100], second[100], result;
 
    printf("Enter first string\n");
    gets(first);
 
    printf("Enter second string\n");
    gets(second);
 
    result = compare_string(first, second);
 
    if ( result == 0 )
       printf("Both strings are same.\n");
    else
       printf("Entered strings are not equal.\n");
 
    return 0;
}
 
int compare_string(char *first, char *second)
{
   while(*first==*second)
   {
      if ( *first == '\0' || *second == '\0' )
         break;
 
      first++;
      second++;
   }
   if( *first == '\0' && *second == '\0' )
      return 0;
   else
      return -1;
}