Problèmes instructions if

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

char lireCharactere();

int main()
{
    char var;

char reponse[10];



do{



var=lireCharactere();

if(var=='a'){printf("ce caractere est une voyelle");}
else if(var=='z'){printf("ce caractere est une consonne");}



printf("continuer?");
scanf("%s", reponse);

}while(strcmp(reponse, "oui")==0);
}

char lireCharactere(){

char charactere;

charactere=getchar();

while (charactere != '\n');

return charactere;

}