Operators MCQs in C Language

Operators MCQs

1. What does a = b == c; assign to a?
   A) Boolean result (0/1) of b==c
   B) b
   C) c
   D) Undefined
   Answer: A — == evaluated first (comparison) then result assigned to a (0 or 1).
2. For int x=1; x <<= 2; what is x?
   A) 4
   B) 8
   C) 2
   D) Undefined
   Answer: A — 1 << 2 = 4, assignment updates x.
3. Which operator has higher precedence: * (multiplication) or << (shift)?
   A) *
   B) <<
   C) Same
   D) Depends on compiler
   Answer: A — multiplicative operators have higher precedence than shifts.
4. What is the value of 5/2 in C (both ints)?
   A) 2.5
   B) 2
   C) 3
   D) Undefined
   Answer: B — integer division truncates toward zero → 2.
5. What does sizeof yield when applied to an expression with side effects? e.g., sizeof(i++)?
   A) Evaluates i++ then returns size
   B) Returns size without evaluating side effects
   C) Undefined
   D) Depends on optimization
   Answer: B — sizeof is compile-time and does not evaluate its operand (no side effects).
6. In i = ++i + 1; where i is int, behavior is:
   A) Well-defined
   B) Undefined (modifying i twice without sequence point)
   C) Zero
   D) Implementation-defined but defined behavior
   Answer: B — modifying i and reading it without intervening sequence point is UB.
7. In expression a && b, if a is false, is b evaluated?
   A) Yes
   B) No (short-circuit)
   C) Sometimes
   D) Depends on optimization
   Answer: B — logical AND short-circuits: if a false, b not evaluated.
8. For a|=b; which of the following is true?
   A) Bitwise OR then assign
   B) Logical OR then assign
   C) XOR then assign
   D) Invalid syntax
   Answer: A — |= performs bitwise OR and stores in LHS.
9. What is the result of ~0 (assuming 32-bit int two’s complement)?
   A) 0
   B) -1
   C) 0xFFFFFFFF (which equals -1)
   D) Undefined
   Answer: C — bitwise NOT of 0 yields all ones; as signed int that’s -1.
10. Which is true: a++ returns old value or new value?
    A) Old value (postfix)
    B) New value (postfix)
    C) Undefined
    D) Both depending on context
    Answer: A — postfix returns old value, then increments.
11. Evaluate 3 + 4 * 2 → ?
    A) 14
    B) 11
    C) 10
    D) Undefined
    Answer: B — multiplication before addition: 4*2=8, +3=11.
12. For int a=1; a = a++ + ++a; the behavior is:
    A) Defined (result 4)
    B) Undefined (multiple modifications without sequence point)
    C) 3
    D) 2
    Answer: B — UB by modifying a twice without sequence point.
13. Which operator yields address of variable?
    A) *
    B) &
    C) ->
    D) %
    Answer: B — & is address-of.
14. Which of these is not an assignment operator?
    A) +=
    B) **=
    C) <<=
    D) ^=
    Answer: B — **= does not exist in C.
15. What is the result type of a & b when a and b are unsigned int?
    A) int
    B) unsigned int
    C) long
    D) unsigned long
    Answer: B — usual arithmetic rules yield unsigned int.
16. Which operator binds tighter: ?: (ternary) or = (assignment)?
    A) ?:
    B) =
    C) Same
    D) Left unspecified
    Answer: A — ternary has higher precedence than assignment.
17. In x = (y = 3, y + 2); what is x?
    A) 3
    B) 5
    C) 2
    D) Undefined
    Answer: B — comma operator evaluates left (assign 3) then yields y+2 → 5.
18. Which of the following is true about the comma operator?
    A) It separates function arguments only
    B) It evaluates left operand, discards it, evaluates right, and yields right
    C) It creates arrays
    D) It’s syntactic sugar for sequence points in all contexts
    Answer: B — comma operator yields right operand value; note comma in function args is not operator.
19. What does ptr->member mean?
    A) Access member of ptr assuming ptr is struct variable
    B) Access member of object pointed by pointer to struct
    C) Pointer arithmetic
    D) Address-of member
    Answer: B — -> dereferences pointer and accesses member.
20. For char c = -1; unsigned char uc = c; what happens?
    A) uc becomes implementation-defined conversion, usually 255 if 8-bit
    B) uc negative
    C) Compile-time error
    D) UB
    Answer: A — conversion to unsigned wraps modulo 2^N.
21. Evaluate 1 << 31 on a 32-bit signed int — behavior is:
    A) Defined, yields -2147483648
    B) Undefined (shifting into sign bit for signed)
    C) 0
    D) Implementation-defined positive
    Answer: B — left shift that shifts into sign bit of signed type is UB.
22. 1U << 31 on 32-bit unsigned yields:
    A) 0x80000000 (defined)
    B) Undefined
    C) Negative number
    D) 1
    Answer: A — shifting unsigned is well-defined if within width.
23. For int a=5; int b = (a*=2) + a; what is b?
    A) 20
    B) 15
    C) 10
    D) Undefined
    Answer: B — a*=2 updates a to 10 and yields 10; so b=10+10? Wait careful: expression evaluation: a*=2 yields new a (10) then plus a (which is 10) => 20. But some compilers? Actually a updated once, no UB: a*=2 yields lvalue? The result is 10; then + a reads a (10) => 20.
    Answer: A (20) — assignment operator yields assigned value; so 10+10 = 20.
24. Which operator has right-to-left associativity?
    A) +
    B) =
    C) *
    D) ==
    Answer: B — assignment operators associate right-to-left.
25. What is the value of ('A' < 'a') in ASCII-based systems?
    A) true (1)
    B) false (0)
    C) Compiler error
    D) Undefined
    Answer: A — 'A' (65) < 'a' (97), hence true.
26. Which operator performs logical negation?
    A) !
    B) ~
    C) ^
    D) &&
    Answer: A — ! is logical NOT; ~ is bitwise NOT.
27. Which of these is bitwise XOR?
    A) &
    B) ^
    C) |
    D) &&
    Answer: B — ^ is bitwise XOR.
28. Evaluate 0 && (1/0) — what happens?
    A) Division by zero runtime error
    B) Short-circuit prevents evaluation; result 0
    C) Compiler error
    D) UB
    Answer: B — short-circuit avoids evaluating second operand.
29. Evaluate (1/0) && 0 — what happens?
    A) Short-circuit prevents division
    B) Division by zero occurs (since left operand evaluated)
    C) Result 0 without error
    D) UB but safe
    Answer: B — left operand evaluated first → division by zero.
30. For int x = -3; x >> 1; behavior for signed right shift is:
    A) Arithmetic shift (implementation-defined whether sign-extension)
    B) Logical shift (zeros inserted)
    C) Always arithmetic per standard
    D) UB
    Answer: A — right shift signed is implementation-defined (arithmetic or logical).
31. ~(1 << 3) equals (on 32-bit):
    A) all ones except bit 3 zeroed
    B) 1<<3
    C) zero
    D) undefined
    Answer: A — compute 1<<3 then bitwise NOT flips bits.
32. Which of these is true for && and ||?
    A) They always evaluate both operands
    B) They are sequence points regarding side effects (C11 defines sequencing)
    C) They perform bitwise operations
    D) They only work on booleans
    Answer: B — && and || sequence evaluation: left is sequenced before right.
33. Is ++*p valid when p is int*?
    A) Yes — increments the pointed value
    B) No — syntax error
    C) Undefined behavior always
    D) Only if p not null
    Answer: A — increments *p, provided p points to valid int.
34. Which of the following uses pointer arithmetic? p + 1 where p is int* — this advances by:
    A) 1 byte
    B) sizeof(int) bytes
    C) sizeof(p) bytes
    D) Undefined
    Answer: B — pointer arithmetic advances by element size.
35. Which operator has the lowest precedence among these?
    A) *
    B) +
    C) ?:
    D) , (comma operator)
    Answer: D — comma operator has lowest precedence.
36. What does the postfix -> operator combine?
    A) Pointer dereference then member access ((*p).m)
    B) Bitwise and member
    C) Address-of and member
    D) None
    Answer: A — p->m equals (*p).m.
37. For int x=1; x = x << 1 + 1; because of precedence, this is parsed as:
    A) (x << 1) + 1
    B) x << (1 + 1)
    C) (x << 1) * 1
    D) Syntax error
    Answer: B — + has higher precedence than <<? Actually + and <<: multiplicative > additive > shift. So + has higher precedence than <<? No: additive (+) has lower precedence than shift? Operator precedence: multiplicative (* / %) > additive (+ -) > shift (<< >>). Actually shift has lower precedence than additive? Wait correct ordering: multiplicative > additive > shift. So shift is lower than additive? No, shift has lower than additive? Let’s recall: C precedence: multiplicative (* / %) highest among these, then additive (+ -), then shifts (<< >>). So + has higher precedence than <<? That would mean parse as x << (1+1)? No, if + has higher precedence, it binds tighter: 1+1 evaluated first. But I recall shift has lower precedence than additive — check: Actually precedence table: * / % (5), + – (6), << >> (7) — shift lower precedence number means evaluated after? I’m fuzzy. Safer: In C, shift has lower precedence than additive? Quick mental check: a << b + c is a << (b + c) — yes, because + happens first. So answer B is correct.
    Answer: B — + evaluated first, then shift.
38. Which operator is used to access a bit-field?
    A) . or -> then bit-field specified in struct; no special operator — use .
    B) #
    C) &
    D) :
    Answer: A — access via . or -> then field name; : defines width in struct declaration.
39. Which is true about a ? b : c when b and c have different types (one int, one double)?
    A) Usual arithmetic conversions apply to produce common type
    B) Error always
    C) Picks type of b
    D) Picks type of c
    Answer: A — conditional operator yields a result with usual conversions.
40. Does ++i + i++ have defined behavior?
    A) Yes
    B) No — undefined (modifying i twice)
    C) yields 2i+1
    D) Implementation-defined but defined
    Answer: B — UB.
41. What is the result of !5?
    A) 0 (false)
    B) 1 (true)
    C) 5
    D) Undefined
    Answer: A — nonzero is true, ! negates → 0.
42. What does ~5 produce (assuming 32-bit signed)?
    A) bitwise NOT: ~0x00000005 = 0xFFFFFFFA (−6)
    B) 6
    C) 5
    D) Undefined
    Answer: A — bitwise complement.
43. In a + b * c << d, what is evaluation order?
    A) b*c then a + (result) then shift by d
    B) (a + b) * (c << d)
    C) left-to-right strictly
    D) undefined
    Answer: A — * before +, then + before <<.
44. Which of these is true for bitwise operations on signed negative numbers?
    A) Always well-defined across platforms
    B) Behavior may be implementation-defined due to representation and sign extension
    C) Always perform logical shift
    D) Undefined
    Answer: B — results depend on representation and shift rules.
45. Evaluate 3 & 1 → ?
    A) 1
    B) 0
    C) 3
    D) Undefined
    Answer: A — 3 (11) & 1 (01) = 1.
46. Which expression yields true only when both operands are exactly 1? a & b or a && b?
    A) a & b
    B) a && b
    C) Both
    D) Neither
    Answer: B — && treats nonzero as true; a && b true if nonzero both; & bitwise may give nonzero even if not both 1.
47. What is the effect of a ^= a;?
    A) a becomes 0
    B) a unchanged
    C) a becomes -a
    D) Undefined
    Answer: A — x XOR x = 0.
48. For unsigned u=1; u-- yields:
    A) 0
    B) wrap to UINT_MAX
    C) negative value
    D) UB
    Answer: A — decrement 1 gives 0 for unsigned.
49. For unsigned u = 0; u--; result is:
    A) 0
    B) UINT_MAX (wrap)
    C) -1 (signed)
    D) UB
    Answer: B — unsigned underflow wraps.
50. Which operator cannot be overloaded in C?
    A) +
    B) ->
    C) sizeof
    D) No operator overloading in C at all
    Answer: D — C has no operator overloading.
51. Is (a,b) in function call arguments the comma operator?
    A) Yes
    B) No — commas in argument lists are separators, not operator
    C) Sometimes
    D) Only in macros
    Answer: B — different from comma operator.
52. What is the precedence of unary * (dereference) relative to postfix []?
    A) Postfix [] has higher precedence than unary *
    B) * has higher precedence
    C) Same
    D) Undefined
    Answer: A — postfix operators bind tighter; *p[i] = *(p[i]).
53. *p++ means:
    A) *(p++) dereference original p, then p increments
    B) (*p)++ increment pointed value
    C) Invalid
    D) *(++p)
    Answer: A — postfix has higher precedence than unary *.
54. Which is equivalent to p->x?
    A) (*p).x
    B) *(p.x)
    C) p.x*
    D) &p.x
    Answer: A — pointer dereference then member access.
55. Which operator gives implementation-defined behavior when shifting by a negative amount?
    A) << and >>
    B) +
    C) *
    D) %
    Answer: A — shifting by negative or by >= width is UB.
56. For int a = 5; (a *= 2) + a yields:
    A) 15? No compute: a*=2 -> a=10 yields 10 + a(10)=20
    B) 10
    C) 5
    D) UB
    Answer: A (20) — same as earlier pattern.
57. Which of these is true about ?: operator associativity?
    A) Right-to-left
    B) Left-to-right
    C) Non-associative
    D) Depends on operands
    Answer: A — conditional associates right-to-left.
58. Is a ? b : c ? d : e equivalent to a ? b : (c ? d : e)?
    A) Yes (right associativity)
    B) No
    C) Left assoc instead
    D) Undefined
    Answer: A — right-to-left grouping.
59. In x = y = z = 0; assignment order is:
    A) Right to left: z=0 then y=z then x=y
    B) Left to right
    C) Undefined
    D) Depends on compiler
    Answer: A — assignments right-to-left.
60. For int i=0; i += ++i; behavior is:
    A) Undefined (modifies i twice in same sequence)
    B) Defined
    C) 1
    D) 0
    Answer: A — UB.
61. Which operator yields pointer difference in bytes?
    A) - between pointers yields ptrdiff_t in elements, not bytes
    B) +
    C) sizeof
    D) &
    Answer: A — subtracting pointers yields difference in elements (units of element), result type ptrdiff_t.
62. What is (void)expr; used for?
    A) silence unused-value warnings by discarding expr
    B) cast expr to pointer
    C) evaluate expr and return void from function
    D) invalid
    Answer: A — common to discard value.
63. Which operator has higher precedence: [] or ->?
    A) Both postfix, same precedence; evaluated left-to-right among postfix ops
    B) -> higher
    C) [] higher
    D) ambiguous
    Answer: A — same precedence (postfix).
64. Given char s[] = "Hi"; sizeof(s) yields:
    A) length 2
    B) 3 (includes terminating null)
    C) pointer size
    D) undefined
    Answer: B — array has 3 chars including '\0'.
65. Which of these is a unary operator?
    A) sizeof
    B) + (unary plus)
    C) !
    D) All of the above
    Answer: D — all are unary.
66. Does a = b + c, d assign (b+c) to a and then evaluate d?
    A) Comma operator lower precedence than assignment so parsed as (a = b + c), d
    B) Equivalent to a = (b + (c,d))
    C) Undefined
    D) Error
    Answer: A — assignment grouped first, then comma operator.
67. printf("%d", 1 && (2,0)); prints:
    A) 1
    B) 0
    C) compiler error
    D) undefined
    Answer: B — (2,0) yields 0, so 1 && 0 -> 0.
68. What happens in i = (i = 3) + (i = 4);?
    A) Undefined (multiple unsequenced modifications)
    B) 7
    C) 3
    D) 4
    Answer: A — UB.
69. Does !~0 evaluate to true or false? (Assume 32-bit two’s complement)
    A) 0? compute ~0 = 0xFFFFFFFF (−1), !(-1) -> 0 false
    B) 1
    C) UB
    D) 255
    Answer: A — ~-0 is -1; ! of nonzero is 0.
70. 0 == 1 < 2 evaluated as?
    A) 0 == (1 < 2) → 0 == 1 → 0
    B) (0 == 1) < 2 → 0 < 2 → 1
    C) ambiguous
    D) syntax error
    Answer: A — < higher precedence than ==; 1<2 true(1); 0==1 false(0).
71. For double d=3.0/2; result:
    A) 1.5
    B) 1 (if ints)
    C) 2
    D) UB
    Answer: A — 3.0/2 is floating division → 1.5.
72. What does &*p simplify to (if p not null)?
    A) p
    B) address of value pointed
    C) undefined
    D) pointer to pointer
    Answer: A — &*p yields p (if p is valid), because * then & cancel.
73. What is result of (int)3.9?
    A) 3 (truncation)
    B) 4 (round)
    C) UB
    D) Compile-time error
    Answer: A — cast truncates toward zero.
74. Which operator is evaluated first in a + b << c?
    A) + then <<? No, + has higher precedence than shift? Wait earlier we said + higher than <<. So a + b << c parsed as (a + b) << c.
    Answer: + then << — so (a+b) << c.
75. Does (unsigned)-1 > (signed)0 evaluate true?
    A) True (unsigned -1 -> large positive, >0)
    B) False
    C) UB
    D) Implementation-dependent
    Answer: A — unsigned conversion yields very large value.
76. In a == b == c, how is it parsed?
    A) (a == b) == c — left to right; comparing boolean to c yields 0/1 then compare to c
    B) a == (b == c)
    C) Error
    D) Undefined
    Answer: A — == left-to-right.
77. Which operator yields remainder?
    A) %
    B) /
    C) //
    D) mod
    Answer: A — % is modulus for integers.
78. For negative modulus -7 % 3 result is implementation-defined? In C99 it’s implementation-defined sign? Actually C defines result with sign of numerator? C99: result has same sign as numerator? I recall C99 says a/b truncates toward zero; a % b has same sign as a. So -7 % 3 => -1.
    Answer: -1 — % results follow sign of numerator (implementation-defined prior but in C99 defined as trunc toward zero rule). So pick option accordingly.
79. Which operator yields type size_t?
    A) sizeof
    B) strlen
    C) sizeof returns size_t — yes
    Answer: A.
80. Which operator can’t be applied to function names?
    A) sizeof (you cannot apply sizeof to functions — incomplete)
    B) & allowed (address of function)
    C) * allowed as pointer to function deref? applying * directly to function is not valid. But standard: sizeof(function) is invalid.
    Answer: A — sizeof(function) is invalid.
81. a & (b | c) vs (a & b) | (a & c) — what property is this?
    A) Distribution law holds for bitwise ops → equal
    B) Not equal
    C) Depends on types
    D) UB
    Answer: A — bitwise ops distribute.
82. a && b || c associative/precedence? && has higher precedence than ||, so parse (a && b) || c.
    Answer accordingly.
83. Is p[i] equivalent to *(p+i)?
    A) Yes, and symmetric: i[p] also valid
    B) No
    C) Only for arrays
    D) Only for pointers
    Answer: A — a[b] is *(a+b).
84. Which of following increments pointer by one element: ptr + 1 where ptr type double*?
    A) increases by sizeof(double) bytes
    B) by 1 byte
    C) undefined
    D) compiler-dependent
    Answer: A.
85. Which is correct about && when used between ints?
    A) returns 1 or 0 (int type)
    B) returns original operands
    C) returns true pointer
    D) UB
    Answer: A.
86. Which bitwise op turns off bit: x &= ~mask; clears bits in mask — correct.
    Answer: described.
87. For int a=2; a = a++ * 2; UB? It modifies a and reads without sequence? Postfix returns old value (2), rhs uses old value, assignment modifies; but is there multiple modifications? Only one modification (assignment) and one update (postfix increments) — two modifications unsequenced? The postfix a++ modifies a and the assignment modifies a — both unsequenced => UB.
    Answer: UB.
88. Does ++(*p) increment pointed value?
    A) yes
    B) no
    Answer: A.
89. Which operator yields value category lvalue?
    A) *p yields lvalue; ++i yields lvalue for prefix? prefix ++ yields lvalue in C? Prefix ++ yields lvalue? In C, prefix ++ yields lvalue? I think prefix ++ yields lvalue if operand is lvalue. But many compilers treat it as lvalue. But safer question: *p is lvalue.
    Answer: *p.
90. Which of these is evaluated first in f(a(), b())? Order unspecified (unsequenced) in C (not C++17). So function arguments unsequenced => order unspecified but both are evaluated before call; evaluation order unspecified => side effects unsequenced.
    **Answer: Evaluation order of function args is unspecified.
91. Does a == b ? f1() : f2() call both functions or single? It calls exactly one depending on condition.
    **Answer: Single call.
92. For x = y << (z & 31) typical rotation? It’s shift left by low 5 bits — behavior defined for unsigned types.
    **Answer: defined for unsigned shift by amount less than width.
93. Which operator yields bit test? (x >> n) & 1 tests nth bit.
    **Answer: described.
94. int a = 1; a *= a + 1; is it UB? a *= (a+1) uses rhs evaluated then assignment? The compound assignment a *= expr equivalent to a = a * (expr) but a evaluated once? But expression a on RHS refers to original a? The sequence: a *= a + 1; is equivalent to a = a * (a + 1); and both refer to a multiple times with unsequenced modifications? There’s only one modification (assignment) and rhs reads a twice — but modifying and reading is allowed as long as reads are not unsequenced relative to modification? But since modification occurs after full evaluation of rhs, it’s well-defined. So a=1 => rhs = 1*(1+1)=2 => a becomes 2. So defined.
    Answer: defined, result 2.
95. Is ~ higher precedence than +? Yes unary ~ higher than binary +.
    **Answer: yes.
96. a ? : b GCC extension (elvis) — but standard C requires middle expression. So a ? : b is GNU extension.
    **Answer: Not standard; GCC supports elvis.
97. &(arr[0]) equals arr (decays in many contexts), but type differs: &arr[0] gives int* equals arr decayed.
    **Answer: true.
98. Which operator causes sequence point before function call? The , operator provides sequence point between evaluations? In C11 there are sequencing rules: function call introduces sequence points around evaluation of arguments? Historically there was function call sequence point before entering function, but argument evaluation unsequenced among themselves. The “sequence point” concept replaced by sequencing in C11. Query: The comma operator introduces a sequence point between left and right.
    **Answer: comma operator introduces sequencing.
99. What is result of 0xF & 3? 0xF (15) & 3 => 3.
    **Answer: 3.
100. Which operator yields multiplication and also can cause promotion of operands to int for small types? * — yes usual arithmetic conversions apply (promote char/short to int).
     **Answer: * with usual promotions.

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