Need help with scanf

[alexanderkwok17]

I try to write a program that identify amounts of sale, and i also need to show an error message when a character is entered;
so i try the following:

#include <stdio.h>

int main(int argc, char **argv){
    int sale1, sale2;
    char c1;
        printf("Amount of Sale (inclusive of GST):");
        scanf("%d.%d", &sale1, &sale2);
        scanf("%c", &c1);
        if (c1 >= 'A' && c1 <= 'Z'){
        printf("Input error\n");
        return 0;
        }else if (c1 >= 'a' && c1 <= 'z'){
        printf("Input error\n");
        return 0;
        }
.....

but when i run the program, if i type
a
it will skip a line and wait for another input. so is there a way to correct this error??
And is it possible to do this just with int, because my teacher want us to do it with just int,(which is without using char).

[weaknessforcats]

scanf will return 0 if the type of the data entered does not match the type of the variable where it is to be stored.

In your case, the a is not an integer. scanf terminates. The next scanf resumes after the a.

To fix the error you can put scanf for the int inside a loop that will continue until scanf returns non-zero.

[alexanderkwok17]

I think i know how to do it now,
i just initialise the value of a to a nnumber,
and then put it in the if statement, so that if a is inputed then a will be the initialise value as well.
And thanks anyways

[weaknessforcats]

The initial value of a is not important. What is important is that you check to see that scanf worked correctly:

int a;
int rval;

    rval = scanf("%d", &a);
    if (rval == 0)
    {
        printf("scanf failed\n");
        return; 
    }
    /* a has the entered value here */