Question

PROBLEM I type y as an option and it prints the text twice before prompting me again when it’s supposed to only print it once.

CORRECT OUTPUT (what im supposed to get but not getting):

Do you order FISH (Y/N)? y
Fish choice (K- Haddock, T- Halibut)

Do you order FISH (Y/N)? y
Fish choice (K- Haddock, T- Halibut)

Do you order FISH (Y/N)? n

Do you order CHIPS (Y/N)? n

Do you order DRINKS (Y/N)? y
Drinks choice (S- Softdrink, C- Coffee, T- Tea)

Do you order DRINKS (Y/N)? n

WRONG OUTPUT (the output I get)

Do you order FISH (Y/N)? y
Fish choice (K- Haddock, T- Halibut)
Do you order FISH (Y/N)? Fish choice (K- Haddock, T- Halibut)
Do you order FISH (Y/N)? y
Fish choice (K- Haddock, T- Halibut)
Do you order FISH (Y/N)? Fish choice (K- Haddock, T- Halibut)
Do you order FISH (Y/N)? n
Do you order CHIPS (Y/N)? Chips choice (C- Cut, R- Ring)
Do you order CHIPS (Y/N)? n
Do you order DRINKS (Y/N)? Drinks choice (S- Softdrink, C- Coffee, T- Tea):
Do you order DRINKS (Y/N)? n

RAW SOURCE (in case you want to compile it yourself and check whats up): http://pastebin.com/raw.php?i=mZ1jVrF0

SOURCE

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

int main() {

    char fishYesNo, chipsYesNo, drinksYesNo;
    char *typeOfFood;

    do {
        typeOfFood = "fish";
        printf("Do you order FISH (Y/N)? ");
        scanf("%c", &fishYesNo);
        if (fishYesNo != 'n') {
            printf("Fish choice (K- Haddock, T- Halibut) \n");

        }
        else if (fishYesNo == 'n') {
            typeOfFood = "chips";
        }

    } while ((strcmp(typeOfFood, "fish")) == 0);

    do {
    typeOfFood = "chips";
        printf("Do you order CHIPS (Y/N)? ");
        scanf("%c", &chipsYesNo);
        if (chipsYesNo != 'n') {
            printf("Chips choice (C- Cut, R- Ring) \n");
        }
        else if (chipsYesNo == 'n') {
            typeOfFood = "drinks";
        }

    } while ((strcmp(typeOfFood, "chips")) == 0);

    do {
    typeOfFood = "drinks";
        printf("Do you order DRINKS (Y/N)? ");
        scanf("%c", &drinksYesNo);
        if (drinksYesNo != 'n') {
            printf("Drinks choice (S- Softdrink, C- Coffee, T- Tea):\n");
        }
        else if (drinksYesNo == 'n') {
            typeOfFood = "fish";
        }

    } while ((strcmp(typeOfFood, "drinks")) == 0);

}

Answer 1

This is a well-known conceptual error in C. The comp.lang.c FAQ (which I suggest you read) has a lot of information on this and other gotchas.

Explanation of what’s happening in your code (comp.lang.c FAQ list · Question 12.18b):

You wanted scanf %c to read a single character, and it tried to, but
when you tried to type that single character at it, before the rest of
the input system would accept it, you had to hit the RETURN key, too.
scanf read only the one character, but that extra newline was still
sitting in an input buffer somewhere, and it’s that extra newline
(seemingly representing a phantom blank line) which was received by
your later input call.

How to deal with it, from a review of scanf‘s problems (comp.lang.c FAQ list · Question 12.20):

It’s nearly impossible to deal gracefully with all of these potential
problems when using scanf; it’s far easier to read entire lines (with
fgets or the like), then interpret them, either using sscanf or some
other techniques.