TO DISPLAY NUMBER OF OCCURRENCE OF LETTER OF GIVEN STRING

#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
    char string[50];
    int count[26],i,j=0,alpha[26],m;
    char letter=97;
    printf("enter the string\n");
    gets(string);
    strlwr(string);
    for(m=0;m<26;m++)
    {
        count[m]=0;
        i=0;
    while(string[i]!=NULL)
    {
        alpha[m]=letter;
        if(alpha[m]==string[i])
        {
            count[m]++;
        }
        i++;
    }
    letter++;
    }
    printf("\nalphabet\t\t\toccurrence\n");
    for(m=0;m<26;m++)
    {
        if(count[m]!=0)
        {
            printf("%c\t\t\t\t%d\n",alpha[m],count[m]);
        }
    }
}