String Concatenation not working in C (TDM-GCC-64)

Question

This is my code

#include <stdio.h>
#include <conio.h>
#include <string.h>
int main()
{
  char fn[20], ln[20], fulln[20];
  int i, j, k;
  printf("Enter your first name: ");
  scanf("%s",fn);
  printf("Enter your last name: ");
  scanf("%s",ln);
  for(i=0,k=0;fn[i]!='\0'; i++, k++)
  {
    fulln[k] = fn[i];
  }
  k++;
  for(j=0;ln[j]!='\0';j++,k++)
  {
    fulln[k] = ln[j];
  }
  fulln[k] = '\0';
  printf("Your full name is %s",fulln);
  return 0;
}

Cannot understand what is wrong with it. It doesn't show the full name. I am using TDM-GCC-64(latest version)

Answer 1

Your code is basically doing a strcpy and strcat manually.

  for(i=0,k=0;fn[i]!='\0'; i++, k++)
  {
    fulln[k] = fn[i];
  }
  k++;
  for(j=0;ln[j]!='\0';j++,k++)
  {
    fulln[k] = ln[j];
  }
  fulln[k] = '\0';

There were problems with your code:

• You should initialise all the char buffer, like this: char fn[20] = "", ln[20] = "", fulln[41] = "";

• Also, you should make sure fulln is big enough to contain both fn and ln . As an example, make it 41 as above, to accommodate a space in between.

• Also, this line k++; should be changed fulln[k++] = ' '; - that adds the space in between.

Btw, as you already include string.h there is no reason why you should not use the standard library strcpy and strcat . That means these two lines can replace your whole section of code:

strcpy(fulln, fn);
strcat(fulln, " ");
strcat(fulln, ln);