程序似乎跳过了 getchar()

Question

So I'm new to coding in C and coding in general. I'm learning with a book and a code in there just won't work and I don't know why. It's probably a trivial matter but as I said..I'm a bloody noob. Anyway this is the code:

#include <stdio.h>

void main()
{
    char a, b;
    
    printf("Welches Zeichen ist groesser?");
    printf("\nGeben Sie ein Zeichen ein:");
    a = getchar();
    printf("Nun ein anderes Zeichen:");
    fflush(stdin);
    b = getchar();
    
    if( a > b)
    {
        printf("'%c' ist groesser als '%c'!\n", a, b);
    }
    else if( b > a)
    {
        printf("\n'%c' ist groesser als '%c'!\n", b, a);
    }
    else
    {
    printf("\nBitte nicht zweimal das gleiche Zeichen eingeben!");
    }
}

I don't get any compiler error messages, it just seems to 'skip' the second getchar and go straight to the last printf. I feel like it has something to do with fflush(stdin). It doesn't matter if it's in the code or not. I already tried fflush(stdout) but with the same outcome. Can somebody tell me why and please don't be too harsh. Thanks in advance!

Answer 1

As pointed out before fflush() is only for output streams, not input.

To read different lines fgets() might be attractive to you. No fflush() required.

If you can get hold of the ANSI final draft of the early C standard it has two sections, the specification and a "rationale" saying why some choices were made. It really helped me learn C in the days. Now days I download and save an ISO final draft to see where C is now.

7.21.5.2 The fflush function

Synopsis

#include <stdio.h> int fflush(FILE *stream);

Description If stream points to an output stream or an update stream in which the most recent operation was not input, the fflush function causes any unwritten data for that stream to be delivered to the host environment to be written to the file; otherwise, the behavior is undefined.

If stream is a null pointer, the fflush function performs this flushing action on all streams for which the behavior is defined above