41. What is the output of: printf("%d", sizeof(main()));
- a) 2
- b) 4
- c) Compilation error
- d) Runtime error
Answer: C - sizeof cannot be applied to function calls, only to types or expressions.
42. Which of these is NOT a valid C standard header file?
- a) stdalign.h
- b) stdnoreturn.h
- c) stdthread.h
- d) stdatomic.h
Answer: C - stdthread.h is not a standard C header (C11 added threads.h instead).
43. What is the purpose of the _Generic keyword in C11?
- a) Generic programming
- b) Memory allocation
- c) Error handling
- d) Thread synchronization
Answer: A - _Generic provides type-generic expressions (similar to function overloading).
44. What is the output of: printf("%d", 1 && -1);
- a) 0
- b) 1
- c) -1
- d) Undefined
Answer: B - Logical AND returns 1 (true) since both operands are non-zero.
45. Which function properly compares two strings case-insensitively?
- a) strcmp()
- b) strncmp()
- c) stricmp()
- d) strcasecmp()
Answer: D - strcasecmp() is the POSIX standard (stricmp() is common but non-standard).
46. What is the value of: 5["abcdef"]
- a) 'a'
- b) 'e'
- c) 'f'
- d) Compilation error
Answer: C - Array indexing is commutative in C (equivalent to "abcdef"[5]).
47. Which qualifier prevents compiler reordering of operations?
- a) const
- b) volatile
- c) static
- d) atomic
Answer: B - volatile tells compiler not to optimize accesses to the variable.
48. What is the output of: printf("%d", 7 & 3);
- a) 1
- b) 3
- c) 5
- d) 7
Answer: B - Bitwise AND of 7 (0111) and 3 (0011) is 3 (0011).
49. Which of these is NOT a valid C11 feature?
- a) Anonymous structures
- b) Type-generic macros
- c) Lambda expressions
- d) Static assertions
Answer: C - Lambda expressions were not added in C11 (they exist in C++).
50. What is the purpose of the 'aligned_alloc' function?
- a) Allocate aligned memory
- b) Allocate array memory
- c) Allocate thread memory
- d) Allocate atomic memory
Answer: A - aligned_alloc(size_t alignment, size_t size) allocates memory with specific alignment.
51. What is the output of: printf("%d", !!10);
- a) 0
- b) 1
- c) 10
- d) -1
Answer: B - First !10 gives 0, then !0 gives 1 (double negation converts to boolean).
52. Which function should be used to safely copy strings?
- a) strcpy()
- b) strncpy()
- c) memcpy()
- d) snprintf()
Answer: D - snprintf() is safest as it guarantees null-termination and bounds checking.
53. What is the value of: (int[]){1,2,3}[1]
- a) 1
- b) 2
- c) 3
- d) Compilation error
Answer: B - This is a compound literal accessing the second element (index 1).
54. Which of these is NOT a valid C99 feature?
- a) Variable-length arrays
- b) Designated initializers
- c) Range-based for loops
- d) Flexible array members
Answer: C - Range-based for loops are a C++ feature, not in C.
55. What is the output of: printf("%d", 1 << 1 + 1);
- a) 1
- b) 2
- c) 3
- d) 4
Answer: D - Addition has higher precedence than shift, so 1 << (1+1) = 1<<2 = 4.
56. Which function converts a wide character string to a multibyte string?
- a) wctomb()
- b) wcstombs()
- c) mbtowc()
- d) mbstowcs()
Answer: B - wcstombs() converts wide character strings to multibyte strings.
57. What is the purpose of the 'static_assert' declaration?
- a) Runtime assertion
- b) Compile-time assertion
- c) Debug assertion
- d) Thread assertion
Answer: B - static_assert (from C11) performs compile-time assertion checking.
58. What is the output of: printf("%d", 0x10 == 16);
- a) 0
- b) 1
- c) 16
- d) Compilation error
Answer: B - 0x10 is hexadecimal for 16, so the comparison is true (1).
59. Which of these is NOT a valid C floating-point constant?
- a) 1.0e-5
- b) 0x1.0p-5
- c) 1.0d-5
- d) 1.0F
Answer: C - C doesn't use 'd' suffix (it's from other languages), 'f' or 'F' is used instead.
60. What is the purpose of the 'fenv.h' header?
- a) File environment
- b) Floating-point environment
- c) Function environment
- d) Format environment
Answer: B - fenv.h provides access to floating-point environment and control modes.