fgeek- storage-modifier ---Storage Classes and Type Qualifiers

Storage Classes and Type Qualifiers

Question 1 WRONG

Which of the following is not a storage class specifier in C?

A	auto
B	register
C	static
D	extern
	volatile
	typedef

Discuss it

Question 1 Explanation: 

volatile is not a storage class specifier. volatile and const are type qualifiers.

Question 4 CORRECT

#include <stdio.h> int main() {     int x = 5;     int * const ptr = &x;     ++(*ptr);     printf("%d", x);         return 0; }

A	Compiler Error
B	Runtime Error
	6
D	5

Discuss it

Question 4 Explanation: 

See following declarations to know the difference between constant pointer and a pointer to a constant. int * const ptr —> ptr is constant pointer. You can change the value at the location pointed by pointer p, but you can not change p to point to other location. int const * ptr —> ptr is a pointer to a constant. You can change ptr to point other variable. But you cannot change the value pointed by ptr. Therefore above program works well because we have a constant pointer and we are not changing ptr to point to any other location. We are only icrementing value pointed by ptr.

Question 5 WRONG

#include <stdio.h> int main() {     int x = 5;     int const * ptr = &x;     ++(*ptr);     printf("%d", x);         return 0; }

	Compiler Error
B	Runtime Error
	6
D	5

Discuss it

Question 5 Explanation: 

See following declarations to know the difference between constant pointer and a pointer to a constant. int * const ptr —> ptr is constant pointer. You can change the value at the location pointed by pointer p, but you can not change p to point to other location. int const * ptr —> ptr is a pointer to a constant. You can change ptr to point other variable. But you cannot change the value pointed by ptr. In the above program, ptr is a pointer to a constant. So the value pointed cannot be changed.

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Macro & Preprocessor

uestion 1 WRONG

#include <stdio.h> #define PRINT(i, limit) do \                         { \                             if (i++ < limit) \                             { \                                 printf("GeeksQuiz\n"); \                                 continue; \                             } \                         }while(1)   int main() {     PRINT(0, 3);     return 0; }

How many times GeeksQuiz is printed in the above program?

	1
B	3
C	4
	Compile-time error

Discuss it

Question 1 Explanation: 

The PRINT macro gets expanded at the pre-processor time i.e. before the compilation time. After the macro expansion, the if expression becomes: if (0++ < 3). Since 0 is a constant figure and represents only r-value, applying increment operator gives compile-time error: lvalue required. lvalue means a memory location with some address.

Assume that size of an integer is 32 bit. What is the output of following program?

#include<stdio.h> struct st {     int x;     static int y; };   int main() {     printf("%d", sizeof(struct st));     return 0; }

A	4
B	8
	Compiler Error
D	Runtime Error

Discuss it

Question 2 Explanation: 

In C, struct and union types cannot have static members. In C++, struct types are allowed to have static members, but union cannot have static members in C++ also.

Question 10 WRONG

Predict the output of following C program

#include<stdio.h> struct Point {   int x, y, z; };   int main() {   struct Point p1 = {.y = 0, .z = 1, .x = 2};   printf("%d %d %d", p1.x, p1.y, p1.z);   return 0; }

	Compiler Error
	2 0 1
C	0 1 2
D	2 1 0

Discuss it

Question 10 Explanation: 

Refer designated Initialization discussed here.

Question 11 CORRECT

What is the use of "#pragma once"?

	Used in a header file to avoid its inclusion more than once.
B	Used to avoid multiple declarations of same variable.
C	Used in a c file to include a header file at least once.
D	Used to avoid assertions

Question 10 WRONG

Which file is generated after pre-processing of a C program?

A	.p
	.i
	.o
D	.m

Discuss it

Question 10 Explanation: 

After the pre-processing of a C program, a .i file is generated which is passed to the compiler for compilation.

Question 9 CORRECT

# include <iostream> # include <string.h> using namespace std;   struct Test {   char str[20]; };   int main() {   struct Test st1, st2;   strcpy(st1.str, "GeeksQuiz");   st2 = st1;   st1.str[0] = 'S';   cout << st2.str;   return 0; }

A	Segmentation Fault
B	SeeksQuiz
	GeeksQuiz
D	Compiler Error

Discuss it

Question 9 Explanation: 

Array members are deeply copied when a struct variable is assigned to another one. SeeAre array members deeply copied? for more details.

uestion 5 WRONG

#include<stdio.h> struct st {     int x;     struct st next; };     int main() {     struct st temp;     temp.x = 10;     temp.next = temp;     printf("%d", temp.next.x);     return 0; }

	Compiler Error
	10
C	Runtime Error
D	Garbage Value

Discuss it

Question 5 Explanation: 

A structure cannot contain a member of its own type because if this is allowed then it becomes impossible for compiler to know size of such struct. Although a pointer of same type can be a member because pointers of all types are of same size and compiler can calculate size of struct

Question 6 CORRECT

Which of the following operators can be applied on structure variables?

A	Equality comparison ( == )
	Assignment ( = )
C	Both of the above
D	None of the above

Discuss it

Question 6 Explanation: 

A structure variable can be assigned to other using =, but cannot be compared with other using ==

Question 7 CORRECT

union test {     int x;     char arr[8];     int y; };   int main() {     printf("%d", sizeof(union test));     return 0; }

Predict the output of above program. Assume that the size of an integer is 4 bytes and size of character is 1 byte. Also assume that there is no alignment needed.

A	12
B	16
	8
D	Compiler Error

Discuss it

Question 7 Explanation: 

When we declare a union, memory allocated for a union variable of the type is equal to memory needed for the largest member of it, and all members share this same memory space. In above example, "char arr[8]" is the largest member. Therefore size of union test is 8 bytes.

union test {     int x;     char arr[4];     int y; };   int main() {     union test t;     t.x = 0;     t.arr[1] = 'G';     printf("%s", t.arr);     return 0; }

Predict the output of above program. Assume that the size of an integer is 4 bytes and size of character is 1 byte. Also assume that there is no alignment needed.

	Nothing is printed
	G
C	Garbage character followed by 'G'
D	Garbage character followed by 'G', followed by more garbage characters
E	Compiler Error

Question 1 WRONG

Which of the following is not a storage class specifier in C?

A	auto
B	register
C	static
D	extern
	volatile
	typedef

Discuss it

Question 1 Explanation: 

volatile is not a storage class specifier. volatile and const are type qualifiers.

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