A simple while loop to check input stuck in infinite loop - c

Question

I am pretty sure this was asked before but I could not find any answers, so here I go. This is a simple line of code and I cannot get it to exit the while loop. If I change the || to && the loop just exit no matter what I press. Thank you for the answers.
#include <stdio.h>
int main()
{
int answer;
printf("Are you sure you want to exit the program? Type in 1 for yes and 2 for no.\n");
scanf("%d", answer);
//This is to check that the user inputs the right number if not error message is displayed
while(answer <1 || answer > 2)
{
printf("Please type in 1 to exit the program and yes and 0 to keep playing. \n");
scanf("%d", answer);
flushall();
}
return 0;
}

Answer 1

If You want to exit on 1, then You just need to check if input is equal to it, that is why I want to scan for more answers when it is not equal to 1. If it is then it will omit while loop and go directly to return 0.
Also I changed the way of usage of scanf - when you declare a variable (in Your case answer), system gives it an address in the memory. Then you use scanf to take an input from the user, and after you take the input, you write it on the address of that variable so that when you refer to it later, the system goes to the address and retrieve the value.
int main()
{
int answer;
printf("Are you sure you want to exit the program? Type in 1 for yes and 2 for no.\n");
scanf("%d", &answer);
//This is to check that the user inputs the right number if not error message is displayed
while(answer != 1)
{
printf("Please type in 1 to exit the program and yes and 0 to keep playing. \n");
scanf("%d", &answer);
}
return 0;
}

Answer 2

This is one the frequent cases of misunderstanding/forgetting how scanf works.
int scanf ( const char * format, ... );
reads formatted data from stdin.
It reads data from stdin and stores data according to the parameter format into the locations pointed by the additional arguments.
The additional arguments should point to already allocated objects of the type specified by their corresponding format specifier within the format string.
It means that arguments should be pointers.
In your case:
int answer;
scanf("%d", answer);
answer is not a pointer but the variable (object) of type int.
To satisfy the scanf you have to use a pointer to the answer.
You can do it using the unary or monadic operator & which gives the address of a variable.
scanf("%d", &answer);
or you could use a pointer pointing to the answer:
int answer;
int answer_ptr = & answer;
scanf("%d", answer_ptr);
which is also correct but typically there is no need to go for this construction.
Secondly the line:
while(answer <1 || answer > 2)
You may want to modify it to
while (answer != 1 && answer != 2)
if you are interested in breaking the while loop when answer is being equal to 1 or 2.