[C] Write sub-string from 0-length by line

/*
pr
pro
prog
progr
progra
program
*/

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

main()
{
      char string[100];
      int c, k, length;

      printf("Enter a string\n");
      gets(string);

      length = strlen(string);

      for ( c = 0 ; c < length ; c++ )
      {
          for( k = 0 ; k <= c ; k++ )
          {
               printf("%c", string[k]);
          }
          printf("\n");
      }

      return 0;
}