Variable not Updating, While Loop not working - c

Question

I am working on an accumulator that asks for different inputs and based on those inputs, updates values in an accumulator. My loop however, doesn't seem to run when I ask for a decimal, hexadecimal, or octal to be inputed. Could someone possibly take a look and give some suggestions to fix it? Thank you! Also Im suppose to somehow use a while loop in my print_menu() function that will check is the input is valid. Any suggestions?
#include <stdio.h>
#include <string.h>
short get_operand(char mode);
void print_acc(short acc);
char print_menu(void);
int main(void);
int main(){
char mode = 'D';
short acc = 8;
char input[10];
char option;
char valid_input[7] = "OHDCSQ";
while (mode != 'Q'){
print_acc(acc);
print_menu();
scanf("%s", &input);
printf("%s\n", input);
option = (char) toupper(input[0]);
switch(option){
case 'O':
mode = 'O';
printf("mode\n");
printf("Mode is Octal\n");
break;
case 'H':
mode = 'H';
printf("Mode is Hexadecimal\n");
break;
case 'D':
mode = 'D';
printf("Mode is Decimal\n");
break;
case 'C':
acc = 0;
break;
case 'S':
get_operand(mode);
if (mode == 'H'){
scanf("%hx", &acc);
printf("%hx", acc);
print_acc(acc);
}
else if (mode == 'O'){
scanf("%ho", &acc);
printf("%ho", acc);
print_acc(acc);
}
else{
scanf("%hd", &acc);
printf("%hd", acc);
print_acc(acc);
}
case 'Q':
mode = 'Q';
printf("\n");
break;
}
//return acc;
}
}
void print_acc(short acc){
printf("\n");
printf("****************************************\n");
printf("* Accumulator: *\n");
printf("* Hex : %04hx *\n", acc);
printf("* Octal : %08ho *\n", acc);
printf("* Decimal : %06hd *\n", acc);
printf("****************************************\n");
}
char print_menu(void){
printf("\n");
printf("Please Select one of the following options:\n");
printf("O Octal Mode\n");
printf("H Hecadecimal Mode\n");
printf("D Decimal Mode\n");
printf("\n");
printf("C Clear Accumulator\n");
printf("S Set Accumulator\n");
printf("\n");
printf("Q Quit\n");
printf("\n");
printf("Option: ");
}
short get_operand(char mode){
switch(mode){
case 'H':
printf("Enter Hex value:");
break;
case 'O':
printf("Enter Octal value:");
break;
default:
printf("Enter decimal value: ");
break;
}
return mode;
}

Answer 1

In the 'S' case where you read in a number, you forget to add a break statement at the end of the case. This results in the code falling through to the Q case which causes the loop to exit.
Add the break and the loop will continue as expected:
case 'S':
...
break;
case 'Q':
...
This is also incorrect:
scanf("%s", &input);
%s expects a char *, but you're passing the address of an array (a char (*)[10] to be presice). Pass in the array directly, which will decay to a pointer to the first element to yield the correct type:
scanf("%s", input);
Also, change print_menu and get_operand to return void, since you're not using the return value and in the former case failing to include one.