Scanf with pointers in C - c

Question

I have some code, but I'll shorten it to show only the relevant parts.
// Displays the list of user’s options available
//Displays the user’s selections and sets the value of the choice
void mainMenu(int *choice);
//Displays the types of account they would like to access and sets the
//value of the chosen account type
void AccountMenu(char *typeAcct);
//Prompts the user for the amount of their deposit and updates the selected account
void DepositMoney(double *currBal);
//Asks the user if they want another transaction
void Repeat(char * doAgain);
int main(){
int choice = 0;
char repeat = 'y';
double checkBal = 575.0,
saveBal = 3750.0,
credBal = 450.0;
char typeAcct;
while(repeat!='n'){
mainMenu(&choice); //get action from user
AccountMenu(&typeAcct); //get account to perform action on from user
switch (choice){
case 1:
switch (typeAcct){
case 'c':
DepositMoney(&checkBal);
break;
case 's':
DepositMoney(&saveBal);
break;
case 'r':
DepositMoney(&credBal);
break;
} //case 1
break;
}
Repeat(&repeat);
repeat = tolower(repeat);
}
}
// Displays the list of user’s options available
//Displays the user’s selections and sets the value of the choice
void mainMenu(int *choice){
printf("Bank Program\n\n");
printf("Please enter your choice:\n");
printf("[1] Deposit\n");
printf("[2] Withdraw\n");
printf("[3] Balance Inquiry\n\n >> ");
scanf(" %d", choice);
}
//Displays the types of account they would like to access and sets the
//value of the chosen account type
void AccountMenu(char *typeAcct){
char choice;
printf("Please enter your choice:\n");
printf("[C] Checking\n");
printf("[S] Savings\n");
printf("[R] Credit\n\n >> ");
scanf(" %c", &choice);
*typeAcct = tolower(choice);
}
//Prompts the user for the amount of their deposit and updates the selected account
void DepositMoney(double *currBal){
printf("Depositing money.\nHow much would you like to deposit?\n\n >> ");
double amount = 0; //deposit amount
scanf(" &f", &amount);
*currBal = *currBal + amount;
}
void Repeat(char * doAgain){
printf("Would you like to perform another transaction? (y/n)\n\n >> ");
scanf(" &c", doAgain);
}
When I execute this code, it runs mostly fine. For example, if I enter "1" for mainMenu and "c" for AccountMenu, choice and typeAcct are both indeed set to "1" and "c" respectively.
The problem doesn't seem to be with the loop. I've tried taking out the loop and only running it once and it still doesn't work. What happens is that after inputting the amount of money I would like to deposit, the value of the variable isn't updated and mainMenu and AccountMenu are run again (even when DepositMoney is the last line of code in the main function and there is no loop). Why does this happen?

Answer 1

1) Incorrect scanf() usage
double amount = 0;
// scanf(" &f", &amount);
scanf(" %lf", &amount);
// scanf(" &c", doAgain);
scanf(" %c", doAgain);
2) Insure your compiler warning are fully enabled. This is the most important bit as most problems are quickly identified this way.
3) Always check the return value of scanf(). BTW, the leading space in " %f" is not needed as "%f" scans over leading white-space anyways. Good though, to have with " %c".
if (scanf("%lf", &amount) != 1) Handle_Error();
4) tolower() take an int. In the rare siuation where a user enters a char in the range \x80 to \xFF, the conversion of char to int is a sign extend and likely a negative number. Unfortunately, this does not work for tolower() which is well defined for 0 to 255 and EOF, but not other negative values.
// repeat = tolower(repeat);
repeat = tolower((unsigned char) repeat);
...
// *typeAcct = tolower(choice);
*typeAcct = tolower((unsigned char) choice);