WAP to accept two strings and concatenate them without using string functions : C Program

/* WAP to accept two strings and concatenate them without using string functions */

#include<stdio.h>
#include<conio.h>

void main()
{
 char str1[20],str2[20],ch;
 int i,j,len=0;
 clrscr();

 printf("Enter 1st string : ");
 scanf("%s",&str1);
 printf("Enter 2nd string : ");
 scanf("%s",&str2);

 printf("\nBefore concatenate : \n");
 printf("String 1 : %s",str1);
 printf("\nString 2 : %s",str2);

 //calculating length of 1st string
 for(i=0;str1[i]!=0;i++)
 {
  len=len+1;
 }

 //concatenate logic without string function
 for(i=len,j=0;str2[j]!=0;i++,j++)
 {
  str1[i]=str2[j];
 }
 str1[i]='\0';//mentioning end of string

 printf("\nAfter concatenate : \n");
 printf("String 1 : %s",str1);
 printf("\nString 2 : %s",str2);

 getch();
}

Output screens :