mengganti suatu huruf menjadi huruf lain sesuai inputan user ( Array )

#include<stdio.h>
#include<conio.h>
#include<string.h>
main()
{
 clrscr();
 char x,y,kalimat[10];
 int z;
 printf("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =\n\n");
 printf("***************** P R O G R A M   P E N G G A N T I   H U R U F **************** \n");
 printf("********************** S E S U A I   I N P U T A N  U S E R ********************\n");
 printf("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =\n\n");
 printf("SILAHKAN MASUKAN KATA / KALIMAT           : ");gets(kalimat);
 printf("\nMASUKAN HURUF YANG AKAN DI GANTI          : ");scanf("%s",&y);//sesuaikan dengan huruf pada kata
 printf("MASUKAN PENGGANTI HURUF                   : ");scanf("%s",&x);
 for(z=0;z<strlen(kalimat);z++)
 {if(kalimat[z]==y)
  {kalimat[z]=x;}}
 printf("\n\nHASIL PERGANTIAN HURUF                    : %s",kalimat);
 getch();
}

kerenkan,,,,