Quiz for Unions definition and usage

Q1: What is a union in C?

A. A special data type where all members share the same memory location B. A data structure with separate memory for each member C. A function pointer D. A dynamic array

Q2: What is the size of a union?

A. Equal to the size of its largest member B. Sum of all member sizes C. Always 4 bytes D. Always 8 bytes

Q3: How do you define a union named "Data"?

A. union Data { int i; float f; }; B. struct Data { int i; float f; }; C. typedef union Data; D. union Data();

Q4: Can union members be accessed like struct members?

A. Yes, using dot operator B. No, only pointers C. Only using arrow operator D. No, must use special functions

Q5: What happens if you assign value to multiple union members?

A. Only the last assigned value is retained B. All values are retained separately C. Compiler error D. Undefined behavior

Q6: Which use case is typical for unions?

A. Saving memory by overlapping variables B. Grouping unrelated variables C. Function parameter passing D. File handling

Q7: Can a union contain other unions?

A. Yes, nested unions are allowed B. No, unions cannot be nested C. Only structs can be nested D. Only pointers to unions

Q8: Is it legal to define pointers to unions?

A. Yes B. No C. Only with typedef D. Only in C++

Q9: How to declare a variable "d" of union Data?

A. union Data d; B. Data d; C. struct Data d; D. typedef Data d;

Q10: Which of these operators accesses union members?

A. Dot operator (.) B. Arrow operator (->) C. Both A and B D. Neither

Q11: Can unions have member functions?

A. No, C unions cannot have functions B. Yes, like C++ C. Yes, always D. Only static functions

Q12: Are unions useful for type punning?

A. Yes, commonly used for this B. No, only structs C. Only in C++ D. Only in macros

Q13: Can you use sizeof on a union variable?

A. Yes, returns size of largest member B. No, not allowed C. Only for structs D. Only for arrays

Q14: How many members can a union hold at the same time?

A. Only one member value at a time B. All members simultaneously C. Depends on compiler D. Only static members

Q15: What happens if you read a different member than last written?

A. Result is implementation-dependent B. Always the last written value C. Compiler error D. Runtime error

Q16: Can unions have bit-fields?

A. Yes, unions can include bit-fields B. No, only structs C. Only with special compiler flags D. Only in C++

Q17: Can unions be initialized at declaration?

A. Yes, but only the first member B. No initialization allowed C. All members must be initialized D. Only with typedef

Q18: Is it possible to assign one union variable to another?

A. Yes, direct assignment is allowed B. No, use memcpy only C. Only pointers can be assigned D. Only with typedef

Q19: What is a common application of unions in embedded systems?

A. Memory-efficient hardware register mapping B. Dynamic memory management C. File handling D. Network programming