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cfunctionrecursionselfgetchar

What does this program do? (Self calling main function + getchar)

Can anybody help me explain this question from a past exam paper? When I compile it, it is never satisfied with any input. Also, what is the reason for the self calling main function?

What does the following program do? Justify your answer.

#include <stdio.h>
int main ( void ) {
    int c;
    if (( c = getchar() ) != EOF) {
        main();
        printf("%c", c);
    }
    return 0; 
}
Solution

  • The program is satisfied, by the EOF returned by getchar(), achieved by entering Ctrl^Z (Windows console) or Ctrl-D (Linux). The program will continue to recurse until that happens (unless the stack breaks). After getting EOF it drops out of all the recursion printing the inputs in reverse order (including a character representing EOF).

    Note that the EOF typed must be the first keystroke after an Enter key.