WBJECA 2025 — Computer PYQ

Understanding how memory is allocated for user-defined types in C is essential for efficient programming.

• Structures (struct): Each member of a structure has its own unique memory location. The total size of a structure is at least the sum of the sizes of its members, often including additional bytes for memory alignment (padding) to ensure efficient CPU access.

• Unions (union): All members of a union share the same memory location. Therefore, a union can only hold the value of one member at a time. The size of the union is determined by the member with the largest size.

We can represent the memory allocation logic mathematically as:

$$\text{Size of Union}=\max (\text{size}(m_1),\text{size}(m_2),\dots ,\text{size}(m_n))$$

$$\text{Size of Structure}\approx \sum _{i=1}^n\text{size}(m_i)+\text{Padding}$$

• Option (A) is false: This describes a union, not a structure.

• Option (B) is false: This describes a structure, not a union.

• Option (D) is false: Structures often include compiler-added padding bytes to align data members for hardware optimization.

Therefore, statement (C) correctly describes the behavior of a union in C.