c programlama anlayanlar

#include <stdio.h>
4. include <math.h>
5. include <stdlib.h>
6. include <string.h>

void main(){
char o;
char e;
int sayi1,sayi2,sayi3;
while(e!='e'){
printf("A or a for addition,nS or s for subtraction,nM or m for multiplication,nD or d for division,nO or o for mod operation.n");
scanf("%c",&o);
printf("Enter first number : ");
scanf("%d",&sayi1);
printf("Enter second number : ");
scanf("%d",&sayi2);

switch(o){

case 'A':
sayi3=sayi1+sayi2;
printf("Addition : %d+%d=%dn",sayi1,sayi2,sayi3);
break;

case 'a':
sayi3=sayi1+sayi2;
printf("Addition : %d+%d=%dn",sayi1,sayi2,sayi3);
break;

case 'S':
sayi3=sayi1-sayi2;
printf("Subtraction : %d-%d=%dn",sayi1,sayi2,sayi3);
break;

case 's':
sayi3=sayi1-sayi2;
printf("Subtraction : %d-%d=%dn",sayi1,sayi2,sayi3);
break;

case 'M':
sayi3=sayi1*sayi2;
printf("Multiplication : %d*%d=%dn",sayi1,sayi2,sayi3);
break;

case 'm':
sayi3=sayi1*sayi2;
printf("Multiplication : %d*%d=%dn",sayi1,sayi2,sayi3);
break;

case 'D':
if(sayi2==0){
printf("Divisor can't be 0n%d/0 = Division by zeron",sayi1);
printf("Enter second number again : ");
scanf("%d",&sayi2);
}
sayi3=sayi1/sayi2;
printf("Division : %d/%d=%d",sayi1,sayi2,sayi3);
break;

case 'd':
if(sayi2==0){
printf("Divisor can't be 0n%d/0 = Division by zeron",sayi1);
printf("Enter second number again : ");
scanf("%d",&sayi2);
}
sayi3=sayi1/sayi2;
printf("Division : %d/%d=%d",sayi1,sayi2,sayi3);
break;

case 'O':
sayi3=sayi1%sayi2;
printf("Mod operation : mod%d(%d)=%d",sayi2,sayi1,sayi3);
break;

case 'o':
sayi3=sayi1%sayi2;
printf("Mod operation : mod%d(%d)=%dn",sayi2,sayi1,sayi3);
break;

}

printf("Press e or E to exitn");
scanf("%c",&e);

}

system("pause");
}

beyler bu programda ne sorun var en sonda e yazdığım zaman while döngüsünden çıkmıyor bi yardımcı olursanız takunuzu yiyem