Conversion from Decimal to Binary, Octal and Hexadecimal

#include <stdio.h>

int main()
{
int numb=0;
char choice=' ';
int index=0;
char arr_numb[16];
char response='y';
while(response=='Y'||response=='y')
{
printf("What do you want to do?\n");
printf("Convert a Decimal number to: ");
printf("\n\tA. Binary Number");
printf("\n\tB. Octal Number");
printf("\n\tC. Hexadecimal Number");
printf("\n\tD. Exit");
printf("\nEnter a Choice[A|B|C|D]");
scanf("%c", &choice);
fflush(stdin);
printf("Enter a number");
scanf("%d", &numb);
index=0;
for(ctr=numb;ctr>=0;ctr--)
{

if (choice=='a'||choice=='A')
{
printf("%d/2/t%d/t%d",ctr,ctr/2,ctr%2);
ctr=ctr/2;
arr_numb[index]=(char)ctr%2;
}
elseif (choice=='b'||choice=='B')
{
printf("%d/8/t%d/t%d",ctr,ctr/8,ctr%8);
ctr=ctr/8;
arr_numb[index]=(char)ctr%8;
}
elseif (choice=='c'||choice=='C')
{
printf("%d/16/t%d/t%d",ctr,ctr/16,ctr%16);
ctr=ctr/16;
if ctr%16==10
arr_numb[index]='A';
elseif ctr%16==11
arr_numb[index]='B';
elseif ctr%16==12
arr_numb[index]='C';
elseif ctr%16==13
arr_numb[index]='D';
elseif ctr%16==14
arr_numb[index]='E';
elseif ctr%16==15
arr_numb[index]='F';
else
arr_numb[index]=(char)ctr%16;
}
else
exit(0);
index++;
}
printf("The ");
if (choice=='a'||choice=='A')
printf("binary ");
elseif (choice=='b'||choice=='B')
printf("octal ");
elseif (choice=='c'||choice=='C')
printf("hexadecimal ");

printf("equivalent of %d is ", numb);
for( ;index >=0; index++)
{
printf("%c",arr_numb[index]);
}

printf("Try Again?[Y|N]:");
scanf("%c", &response);
fflush(stdin);

}
return 0;
}