Quiz: Files and Preprocessor

5 questionsNo time limitPass: 60%+10 XP on first pass

Read and write files with fopen, fprintf, fscanf and fgets, check for errors, use command-line arguments, and master the preprocessor: #define, macros, #include and header guards.

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Question 1
What does fopen return if the file can't be opened?
0-1NULLAn empty file

Question 2

What does this print?

#include <stdio.h>
#define DOUBLE(x) x + x
int main(void) {
    printf("%d", DOUBLE(3) * 2);
    return 0;
}

129618

Question 3
Which mode adds data to the end of an existing file?
"w""r""a""x"
Question 4
What is the purpose of a header guard (#ifndef … #define … #endif)?
To make code fasterTo prevent the same header from being included twiceTo hide functions from other filesTo declare main
Question 5
When does the preprocessor run?
After linkingBefore compilationAt runtimeOnly in debug mode