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- Question
There exists a way to prevent the same file from getting #included twice in the same program.
Options- A. True
- B. False
- Correct Answer
- True
ExplanationTrue, 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
C Preprocessor problems
Search Results
- 1. 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.- 2. 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)
- 3. 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.- 4. A preprocessor directive is a message from compiler to a linker.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
FALSEExample: #define symbol replacement
When the preprocessor encounters #define directive, it replaces any occurrence of symbol in the rest of the code by replacement. This replacement can be an statement or expression or a block or simple text.
- 5. In a macro call the control is passed to the macro.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
False, Always the macro is substituted by the given text/expression.- 6. 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.
- 7. 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 Discuss
Correct Answer: Yes
Explanation:
Yes, 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.
- 8. 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.- 9. 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'- 10. 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.
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