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- Question
Will the program compile successfully?
#include<stdio.h> int main() { #ifdef NOTE int a; a=10; #else int a; a=20; #endif printf("%d\n", a); return 0; }
Options- A. Yes
- B. No
- Correct Answer
- Yes
ExplanationYes, this program will compile and run successfully and prints 20.The macro #ifdef NOTE evaluates the given expression to 1. If satisfied it executes the #ifdef block statements. Here #ifdef condition fails because the Macro NOTE is nowhere declared.
Hence the #else block gets executed, the variable a is declared and assigned a value of 20.
printf("%d\n", a); It prints the value of variable a 20.
C Preprocessor problems
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- 1. Will the following program print the message infinite number of times?
#include<stdio.h> #define INFINITELOOP while(1) int main() { INFINITELOOP printf("CuriousTab"); return 0; }
Options- A. Yes
- B. No Discuss
Correct Answer: Yes
Explanation:
Yes, the program prints "CuriousTab" and runs infinitely.The macro INFINITELOOP while(1) replaces the text 'INFINITELOOP' by 'while(1)'
In the main function, while(1) satisfies the while condition and it prints "CuriousTab". Then it comes to while(1) and the loop runs infinitely.
- 2. There exists a way to prevent the same file from getting #included twice in the same program.
Options- A. True
- B. False Discuss
Correct Answer: True
Explanation:
True, We can prevent the same file from getting included again by using a preprocessor directive called #ifndef (short for "if not defined") to determine whether we've already defined a preprocessor symbol called XSTRING_H. If we have already defined this symbol, the compiler will ignore the rest of the file until it sees a #endif (which in this case is at the end of the file).#ifndef XSTRING_H
#define XSTRING_H defines the same preprocessor symbol,
Finally, the last line of the file, #endif
- 3. Macros have a local scope.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
False, The scope of macros is globals and functions. Also the scope of macros is only from the point of definition to the end of the file.- 4. Macros with arguments are allowed
Options- A. True
- B. False Discuss
Correct Answer: True
Explanation:
True, A macro may have arguments.Example: #define CUBE(X)(X*X*X)
- 5. A macro must always be defined in capital letters.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
FALSE, The macro is case insensitive.- 6. Would the following typedef work?
typedef #include l;
Options- A. Yes
- B. No Discuss
Correct Answer: No
Explanation:
Because typedef goes to work after preprocessing.- 7. Will the program compile successfully?
#include<stdio.h> #define X (4+Y) #define Y (X+3) int main() { printf("%d\n", 4*X+2); return 0; }
Options- A. Yes
- B. No Discuss
Correct Answer: No
Explanation:
Reports an error: Undefined symbol 'X'- 8. It is necessary that a header files should have a .h extension?
Options- A. Yes
- B. No Discuss
Correct Answer: No
Explanation:
No, the header files have any kind of extension.- 9. Will the program compile successfully?
#include<stdio.h> int main() { printf("India" "CURIOUSTAB\n"); return 0; }
Options- A. Yes
- B. No Discuss
Correct Answer: Yes
Explanation:
Yes, It prints "CuriousTab"- 10. Will it result in to an error if a header file is included twice?
Options- A. Yes
- B. No
- C. It is compiler dependent. Discuss
Correct Answer: It is compiler dependent.
Explanation:
Unless the header file has taken care to ensure that if already included it doesn't get included again.
Turbo C, GCC compilers would take care of these problems, generate no error.
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- 1. Will the following program print the message infinite number of times?