output suddenly separate int with space

Question

int sales[ 1 ];
do
{
    scanf_s( "%d", sales, 1 ); 

    printf( "\n%d\n", sales[ 0 ] );

    printf( "\nyou got weekly income of $ %d\n\n", commision( sales[ 0 ] ) );

} while ( sales[0] >-1 );

I want to ask, why every time i input int with space (example 123 456), the output is sales[0]=123 then suddenly it automatically assign 456 to sales[0], can you guys explain it why?

Answer 1

What your code does is that it reads a signed number from the standard input. ( %d does read until the whitespace but ignores the whitespace itself.) It then writes that number (the first number would be 123 ) to your sales array at index 0 . Then you're writing the return value of your commision(...) function to standard output.

then suddenly it automatically assign 456 to sales[0]

If by that you mean that at the end of the program's execution sales[0] contains 456 instead of 123 it is because the whole procedure I described above is done as long as your do while loop runs. And if sales[0] is greater than -1 which is the case for sales[0] being 123 after the first procedure it will run again and read 456 from the standard input and write that to the sales array.

Some more examples for scanf_s("%d", int_pointer, 1) reading input from stdin :

• Input 42 43ab 44 would be read in 3 different scanf_s as 42 , 43 and 44 .
• Input 42 a would be read in 2 different scanf_s as 42 and 0 .
• Input 42 a a43 44 would be read in 4 different scanf_s as 42 , 0 , 0 and 44 .

Answer 2

Because scanf is picky and it wants the exact input of one number. To it the whitespace signals the end of the desired input format.

123[whitespace] -> 123 is assigned, stuff happens, loops again.

456[whitespace] -> 456 is assigned, stuff happens, loops again.

Answer 3

int commission(int i) {
    return 42*i;
}

int main(int argc, const char * argv[]) {
    int sales[ 1 ];
    do
    {
        scanf_s( "%d", sales, 1 );

        printf( "\n%d\n", sales[ 0 ] );

        printf( "\nyou got weekly income of $ %d\n\n", commission( sales[ 0 ] ) );
        sales[0] = -1; // Won't jump to the next value
    } while ( sales[0] >-1 ); // But then what's the point of the loop?

    return 0;
}