What will be the size of the following structure? struct test { char c; int i; float f; };

The correct answer is D: Depends on padding and alignment. Size depends on compiler's padding and alignment rules. Typically 12 bytes with padding, but varies by system.

A program reads structured data: fread(ptr, sizeof(struct), count, fp). If fread() returns a value less than 'count', what could be the reason?

The correct answer is A: End of file reached before reading all items. fread() returns the number of items actually read. If less than 'count' is returned, it indicates EOF was reached or a read error occurred before completing the request.

Which scenario is most likely to cause a segmentation fault in dynamic memory?

The correct answer is B: Accessing memory beyond allocated size. Buffer overflow by accessing beyond allocated boundaries causes segmentation fault as it accesses invalid memory pages.

Consider union u { int i; char c; float f; }; What is the size of this union?

The correct answer is A: 4 bytes. Union size equals the largest member size. float is typically 4 bytes, which is largest.

Which statement is true about the goto statement in modern C programming?

The correct answer is B: It is legal but generally discouraged for code clarity. goto is valid in C but discouraged in modern programming as it reduces code readability. However, it has legitimate uses in cleanup code and error handling.

Home

Home › Subjects › C Programming › Arrays & Strings

C Programming
Arrays & Strings

C language from basics to advanced placement prep

21 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 21

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.1 Hard Arrays & Strings

What does the strspn() function do?

A Finds substring in a string

B Spans the initial segment containing only characters from specified set

C Compares two strings

D Reverses a string

Correct Answer: B. Spans the initial segment containing only characters from specified set

EXPLANATION

strspn(str, charset) returns length of initial segment of str containing only characters from charset. Useful for token parsing.

Test

Q.2 Hard Arrays & Strings

In what scenario would you use memcpy() instead of strcpy()?

A memcpy() is always faster

B When copying binary data or strings without null terminators

C When the destination is smaller

D memcpy() is safer

Correct Answer: B. When copying binary data or strings without null terminators

EXPLANATION

strcpy() assumes null-terminated strings. memcpy() copies exact number of bytes, suitable for binary data or embedded nulls.

Test

Q.3 Hard Arrays & Strings

Which of the following correctly declares a pointer to an array (not array of pointers)?

A int *arr[5];

B int (*ptr)[5];

C int [5]*ptr;

D int &arr[5];

Correct Answer: B. int (*ptr)[5];

EXPLANATION

Parentheses change precedence. int (*ptr)[5] is pointer to array of 5 ints. int *arr[5] is array of 5 pointers.

Test

Q.4 Hard Arrays & Strings

In string handling, what is the difference between fgets() and gets()?

A fgets() is slower

B fgets() includes newline character, gets() doesn't

C fgets() takes size parameter and is safer; gets() is unsafe (removed from C11)

D gets() works only with integers

Correct Answer: C. fgets() takes size parameter and is safer; gets() is unsafe (removed from C11)

EXPLANATION

gets() has no buffer overflow protection and was removed in C11. fgets(str, size, stdin) is the safer alternative with size limiting.

Test

Q.5 Hard Arrays & Strings

For a 3D array int arr[2][3][4], what is arr[1][2][3] equivalent to?

A arr + 2*3*4 + 2*4 + 3

B arr + 1*3*4 + 2*4 + 3

C arr + 3 + 2 + 1

D arr + 1 + 2 + 3

Correct Answer: B. arr + 1*3*4 + 2*4 + 3

EXPLANATION

In row-major order: address = base + (i*m*n + j*n + k) where m=3, n=4. So arr[1][2][3] = base + 1*12 + 2*4 + 3 = base + 23.

Test

Q.6 Hard Arrays & Strings

What potential issue exists with this code: char *ptr = "Hello"; ptr[0] = 'h';?

A Compilation error

B Attempting to modify a string literal (undefined behavior)

C Memory leak

D Syntax error in character assignment

Correct Answer: B. Attempting to modify a string literal (undefined behavior)

EXPLANATION

String literals are stored in read-only memory. Attempting to modify them causes undefined behavior or segmentation fault at runtime.

Test

Q.7 Hard Arrays & Strings

What is the relationship between pointer arithmetic and array indexing in C?

A Pointer arithmetic is faster than array indexing

B arr[i] is equivalent to *(arr + i) - both are mathematically identical

C Array indexing is only for static arrays, pointer arithmetic for dynamic

D No relationship - they are completely different operations

Correct Answer: B. arr[i] is equivalent to *(arr + i) - both are mathematically identical

EXPLANATION

C standard defines arr[i] as *(arr + i). Both notations access the same memory location and perform identically.

Test

Q.8 Hard Arrays & Strings

What is the most efficient way to copy one array to another in C?

A memcpy(dest, src, sizeof(src));

B strcpy(dest, src);

C for loop with element-by-element assignment

D Array assignment dest = src;

Correct Answer: A. memcpy(dest, src, sizeof(src));

EXPLANATION

memcpy() is the most efficient as it performs block memory copy. strcpy() is only for strings, and array assignment doesn't work in C.

Test

Q.9 Hard Arrays & Strings

How should dynamic 1D array of strings be declared for 5 strings of length 20?

A char **str = (char**)malloc(5 * sizeof(char*)); for loop to allocate each string

B char str[5][20];

C char *str[5];

D Both A and C after proper allocation

Correct Answer: A. char **str = (char**)malloc(5 * sizeof(char*)); for loop to allocate each string

EXPLANATION

For dynamic allocation, use double pointer char** and allocate memory for each string separately. Options B and C are static allocations.

Test

Q.10 Hard Arrays & Strings

What will the following code print?
int arr[3] = {10, 20, 30};
int *p = arr;
printf("%d %d", *p++, *++p);

A 10 20

B 10 30

C 20 20

D Undefined behavior

Correct Answer: D. Undefined behavior

EXPLANATION

This code exhibits undefined behavior due to lack of sequence points between modifications and access of p. Different compilers may produce different results.

Test

1 2 3

All Subjects & Topics

Govt. Exams

Entrance Exams

Teacher Exams

Subjects

Quick Links

C Programming Arrays & Strings

C Programming
Arrays & Strings