Find Frequency of Characters in a String

/*
Write a program in C to find frequency of characters in  a string
*/
 
#include<stdio.h>
#include<string.h>

main()
{
char string[100], ch;
int c = 0, count[26] = {0};

printf("Enter a string\n");
gets(string);

while ( string[c] != '\0' )
{
/*
* Considering characters from 'a' to 'z' only
*/

if ( string[c] >= 'a' && string[c] <= 'z' )
count[string[c]-'a']++;

c++;
}

for ( c = 0 ; c < 26 ; c++ )
{
if( count[c] != 0 )
printf("%c occurs %d times in the entered string.\n",c+'a',count[c]);
}

return 0;
}