try yourself |run program

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

void main(){
 char str1[50];
 char str2[50];
 clrscr();
  printf("Enter first string:-");
  gets(str1);
  printf("\nEnter second string:-");
  gets(str2);
  strcat(str1,str2);
  puts(str1);
 getch();
}

Program Output

Enter first string:-This is rose. 
Enter second string:-This is mango. 
This is rose.This is mango.