C Program to Compare Strings without Using String Functions

#include<stdio.h>
char string1[100],string2[100];
int flag=1,len1=0,len2=0;
main()
{
int res;
printf("Enter String-1n");
gets(string1);
printf("Enter String-2n");
gets(string2);
while(string1[len1]!=''){len1++;}
while(string2[len2]!=''){len2++;}
res=compare(string1,string2);
if (res==-1||res==1) process(res);
else if(flag==len1&&flag==len2) process(0); else if(flag==len1&&flag<len2) process(-1); else if(flag==len2&&flag<len1) process(1);
}

process(int a)
{
switch(a)
{
case '1':printf("String-1 [ %s ] Greater than String-2[ %s ]n",string1,string2);
break;
default:printf("String-2[ %s ] Greater than String-1[ %s ]n",string2,string1);
break;
case '0':printf("Strings [ %s ] are Equaln",string1);
break;
}
}

compare(char *a,char *b)
{
int i=0,j=0,len,comp1,comp2;
comp1=a[i];comp2=b[j];
if(comp1>comp2) process(1);
else if(comp1<comp2) process(-1);
else 
{
if(len1>len2) len=len2; else len=len1;
for(j=1;j<len;j++)
{
if(a[j]>b[j]) process(1); else if(a[j]<b[j]) process(-1);
else flag++;
}
}
}

copy(char *a,char *b)
{
int i;
for(i=0;a[i]!='';i++){ b[i]=a[i]; } b[i+1]='';
}