Which storage class has global scope and external linkage by default?

The correct answer is C: extern. Global variables with extern keyword have global scope and external linkage across translation units.

What happens when you increment a pointer? int arr[5] = {1,2,3,4,5}; int *p = arr; p++;

The correct answer is B: p points to the next element of the array. When a pointer is incremented, it moves to the next element based on the data type size (pointer arithmetic).

What is the purpose of using fflush() in file handling, and when is it critical to use it?

The correct answer is B: To write buffered data to the actual file on disk. fflush() writes any buffered data to the underlying file. It's critical when you need to ensure data is written to disk before continuing, especially before reading the same file.

What will this code output? int x = 10; int* getAddress() { return &x; } main() { int *ptr = getAddress(); printf("%d", *ptr); }

The correct answer is A: 10. Since x is static (global scope), returning its address is safe and the pointer remains valid. The output is 10. If x were local, it would be undefined behavior.

What happens when you try to free a pointer that was not allocated by malloc/calloc/realloc?

The correct answer is A: Undefined behavior - likely crash or memory corruption. Calling free() on a pointer that wasn't returned by malloc/calloc/realloc causes undefined behavior, potentially corrupting the heap and crashing the program.

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C Programming
Basics & Syntax

C language from basics to advanced placement prep

40 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 40

Topics in C Programming

All Basics & Syntax 86 Data Types & Variables 97 Control Flow 100 Functions 99 Arrays & Strings 100 Pointers 99 Structures & Unions 100 File Handling 100 Dynamic Memory 98 Preprocessor 99

Q.11 Medium Basics & Syntax

What will be printed by: int arr[3] = {1, 2, 3}; printf("%d", *(arr + 1));

A 1

B 2

C 3

D Undefined

Correct Answer: B. 2

EXPLANATION

arr + 1 points to the second element, so *(arr + 1) dereferences it to give 2.

Test

Q.12 Medium Basics & Syntax

Which of the following statements about NULL is correct?

A NULL is a keyword in C

B NULL is typically defined as (void *)0

C NULL and 0 are interchangeable for pointers

D Both B and C

Correct Answer: D. Both B and C

EXPLANATION

NULL is a macro (not a keyword) typically defined as (void *)0, and can be used interchangeably with 0 for pointer assignments.

Test

Q.13 Medium Basics & Syntax

In C, what is the difference between #include and #include "stdio.h"?

A They are identical

B searches standard directories; "" searches current directory first

C "" is only for user-defined headers

D is only for system headers

Correct Answer: B. searches standard directories; "" searches current directory first

EXPLANATION

Angle brackets search standard include directories, while quotes search the current directory first, then standard directories.

Test

Q.14 Medium Basics & Syntax

Which of the following is a correct way to initialize a character array with a string?

A char str[] = "Hello";

B char str[5] = "Hello";

C char *str = "Hello";

D All of the above

Correct Answer: D. All of the above

EXPLANATION

All three are valid ways to work with strings in C, though they differ in memory allocation and mutability.

Test

Q.15 Medium Basics & Syntax

What will be printed by: printf("%d", sizeof(float));

A 2

B 4

C 8

D Compiler dependent

Correct Answer: B. 4

EXPLANATION

On most systems, sizeof(float) is 4 bytes. Though technically implementation-defined, 4 bytes is standard.

Test

Q.16 Medium Basics & Syntax

What is the correct syntax to define a macro with arguments in C?

A #define MAX(a, b) ((a) > (b) ? (a) : (b))

B #macro MAX(a, b) ((a) > (b) ? (a) : (b))

C #define MAX a, b ((a) > (b) ? (a) : (b))

D define MAX(a, b) ((a) > (b) ? (a) : (b))

Correct Answer: A. #define MAX(a, b) ((a) > (b) ? (a) : (b))

EXPLANATION

The correct syntax uses #define followed by macro name and parameters, with the replacement text in parentheses.

Test

Q.17 Medium Basics & Syntax

What does the 'extern' keyword indicate in C?

A A variable exists in another source file

B A variable is local to a function

C A variable cannot be modified

D A variable is allocated on the stack

Correct Answer: A. A variable exists in another source file

EXPLANATION

'extern' declares a variable or function that is defined in another translation unit (source file).

Test

Q.18 Medium Basics & Syntax

What will be the result of the bitwise operation: 5 & 3 in C?

A 1

B 7

C 6

D 4

Correct Answer: A. 1

EXPLANATION

5 (binary 101) & 3 (binary 011) = 001 (binary) = 1. Bitwise AND operates on each bit position.

Test

Q.19 Medium Basics & Syntax

In C, what is the correct way to pass a variable by reference using pointers?

A void func(int var) { var = 10; }

B void func(int &var) { var = 10; }

C void func(int *var) { *var = 10; }

D void func(int *var) { var = 10; }

Correct Answer: C. void func(int *var) { *var = 10; }

EXPLANATION

C uses pointers for pass-by-reference. The dereference operator '*var' accesses the actual variable. C++ supports references (&var), but C does not.

Test

Q.20 Medium Basics & Syntax

What is the difference between 'break' and 'continue' statements in C?

A 'break' stops execution while 'continue' skips iteration

B Both have the same function

C 'continue' stops execution while 'break' skips iteration

D Neither has practical use in loops

Correct Answer: A. 'break' stops execution while 'continue' skips iteration

EXPLANATION

'break' terminates the loop entirely, while 'continue' skips the current iteration and moves to the next one.

Test

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