Structures & Unions
What is the output of this complex code?
char(1 byte) + padding(3 bytes) + int(4 bytes) = 8 bytes due to alignment requirements.
Consider this structure: struct Complex { int real; int imag; }; If you want to create an array of 100 such structures, which declaration is correct?
A
struct Complex c[100];
B
struct Complex *c = (struct Complex *)malloc(100);
C
struct Complex c = {100};
D
struct Complex c[100][100];
Correct Answer:
A. struct Complex c[100];
Option A correctly creates a static array of 100 structures. Option B creates a pointer (and allocates incorrect size).
What is the purpose of using anonymous structures/unions?
A
To reduce memory usage
B
To access members without using the intermediate struct name
C
To improve execution speed
D
To hide members from external access
Correct Answer:
B. To access members without using the intermediate struct name
Anonymous structures allow direct member access without needing to reference the nested structure name.
In a nested structure scenario like struct A contains struct B, how do you access a member of B from A's variable?
A
a_var->b_member
B
a_var.b_var.c_member
C
Both A and B are correct depending on context
D
a_var..c_member
Correct Answer:
C. Both A and B are correct depending on context
If B is embedded in A: a_var.b_var.member. If B is a pointer in A: a_var->b_var->member or a_var.b_ptr->member.
Which of the following is a valid way to pass a structure to a function?
A
Pass by value only
B
Pass by pointer only
C
Both pass by value and pass by pointer
D
Pass by reference only
Correct Answer:
C. Both pass by value and pass by pointer
Structures can be passed by value (copying the entire structure) or by pointer (passing address) for efficiency.
In the context of structures, what does 'self-referential' mean?
A
A structure that contains a member of the same structure type
B
A structure that refers to global variables
C
A structure that contains only pointers
D
A structure defined within another structure
Correct Answer:
A. A structure that contains a member of the same structure type
Self-referential structures contain pointers to their own type, enabling dynamic data structures like linked lists and trees.
Given: struct Node { int data; struct Node *next; }; This represents which data structure concept?
A
Binary Tree node
B
Singly Linked List node
C
Graph adjacency node
D
Hash table bucket
Correct Answer:
B. Singly Linked List node
A self-referential structure with a single pointer member is the fundamental building block of a singly linked list.
What will happen if you try to compare two structures using the == operator directly?
A
It compares all members automatically
B
It results in a compilation error
C
It returns the comparison of the first members only
D
It compares the memory addresses of the structures
Correct Answer:
B. It results in a compilation error
C does not support direct comparison of structures using ==. You must compare members individually or use memcmp().
Consider a structure with bit fields:
A
1 byte
B
2 bytes
C
4 bytes
D
8 bytes
Correct Answer:
C. 4 bytes
Bit fields must fit within an underlying integer type. Total bits = 8, which requires at least 4 bytes (one int on most systems).
In C, what does the 'typedef' keyword do when used with structures?
A
Creates a new data type that is an alias for the structure
B
Allocates memory for the structure
C
Makes the structure accessible globally only
D
Prevents the structure from being modified
Correct Answer:
A. Creates a new data type that is an alias for the structure
typedef creates an alias, allowing you to use the structure name directly without using 'struct' keyword.
