C++ Data Types MCQs: 12 Fundamental and Derived Type Questions Solved

C++ data-type questions go beyond naming int, bool, or char. They combine case-sensitive keywords, representation assumptions, Boolean conversion, pointer declarations, precedence, and reference aliasing. Choose an option before reading each explanation.

Question-specific pages are unavailable, so each answer opens the C++ Data Types lesson for concept review after your attempt.

C++ data types: build the map before solving

Use bool ready = true;, int marks[3] = {64, 72, 81};, int *ptr = &marks[1];, and int &alias = marks[1];. Initially, *ptr and alias read 72; after alias = 75, marks[1], *ptr, and alias read 75. Array, pointer, and reference are derived; const is a qualifier, not a fundamental type.

For Question 4, C++ guarantees sizeof(char) == 1, but int and float byte sizes are implementation-dependent. The stated 8-bit-byte, 4-byte int, and 4-byte float model makes 1, 4, 4 valid here, not universally.

C++ Data Types MCQs 1-3: valid types, bool, and wide characters

Question 1 (IBPS 2025)

Which of the following is not a valid data type in the C++ programming language?

• A. Float

• B. Int

• C. Real

• D. Char

• E. Double

Correct answer: C. Real.

C++ has the fundamental keywords float, int, char, and double, but no standard built-in keyword real. The answer is C under the question's intended interpretation. The wording has a flaw: C++ is case-sensitive, making the capitalised spellings non-keywords too unless separately declared. Treat those spellings here as labels for the lowercase types.

Question 2 (DSSSB 2021)

In C++, bool data type is used to hold how many values?

• A. n²

• B. 2

• C. 2n

• D. 2ⁿ

Correct answer: B. 2.

A bool represents only false and true. Integer conversion maps them to 0 and 1, but adds no Boolean values. The expressions n², 2n, and 2ⁿ vary with n. The stem asks for a fixed cardinality, which is exactly 2 logical values in this type.

Question 3 (DSSSB 2021)

In C++ a wide-character constant begins with the letter _____.

• A. W

• B. C

• C. L

• D. S

Correct answer: C. L.

'A' is a character literal; L'A' is a wide-character literal. Uppercase L sits before the opening quote, making C correct. W, C, and S are distractors. This syntax does not give wchar_t a fixed byte width across implementations.

C++ Data Types MCQs 4-6: size, round-off, and Boolean conversion

Question 4 (TCS 2024)

What will be the output of the following C++ code, assuming 8-bit bytes, a 4-byte int, and a 4-byte float?

#include<iostream>
using namespace std;
int main()
{
cout << sizeof(char) << " ";
cout << sizeof(int) << " ";
cout << sizeof(float);
return 0;
}

• A. 1 4 4

• B. 1 4 8

• C. 1 8 8

• D. 1 8 2

Correct answer: A. 1 4 4.

Under the stated model, sizeof(char) = 1, sizeof(int) = 4, and sizeof(float) = 4, producing 1 4 4. Only the char result is universally fixed at one C++ byte; the question explicitly supplies the int and float sizes.

Question 5 (Indian Space Research Organization 2008)

Repeated execution of simple computation may cause compounding of

• A. round-off errors

• B. syntax errors

• C. run-time errors

• D. logic errors

Correct answer: A. round-off errors.

Ten additions give 10 × 0.1 = 1.0 mathematically. Binary floating-point may store 0.1 approximately, so repetition can accumulate round-off error. Syntax, run-time, and logic errors are different fault classes; they do not compound in this numerical sense.

Question 6 (BPSC 2023)

What is the value of ‘p’ in the following C++ code snippet?

 #include <iostream>
 using namespace std;
 int main()
 {
     int p;
     bool a = true;
     bool b = false;
     int x = 10;
     int y = 5;
     p = (x || y) + (a + b);
     cout << p;
     return 0;
 }

• A. 12

• B. 16

• C. 2

• D. More than one of the above

• E. None of the above

Correct answer: C. 2.

Because x = 10 and y = 5 are non-zero, (x || y) is true, contributing integer 1. Next, a + b becomes 1 + 0 = 1. Thus p = 1 + 1 = 2. The magnitudes 10 and 5 are not directly added.

C++ Data Types MCQs 7-8: const and declaration compatibility

Question 7 (MPPSC 2025)

In C++, using const keyword we can declare

• A. "I promise not to change this value"

• B. "I promise to change this value"

• C. "I promise to double this value"

• D. "I promise to exchange this value with other value"

Correct answer: A. "I promise not to change this value".

With const int limit = 25;, assignment limit = 30; is not allowed through that name. Option A summarises this no-modification contract. The keyword qualifies a type; it neither creates a fundamental type nor promises doubling or exchange.

Question 8 (DSSSB 2018)

Which of the following is not a correct declaration statement in C++?

• A. int *ptr=0, p;

• B. int p, *ptr = 0;

• C. int p; double *fp = &p;

• D. int *p, *q, r;

Correct answer: C. int p; double *fp = &p;.

In A and B, ptr is an int* and p an int. In D, p and q are int*, while r is an int. In C, &p is an int*, which cannot initialise a double*; these types are incompatible.

C++ Data Types MCQs 9-10: pointer assignment and precedence

Question 9 (DSSSB 2018)

Consider the following C++ code segment:

int a = 10, b = 20;

int *p = &a, *q = &b;

p = q;

With respect to the code segment mentioned above, which of the following statement is correct?

• A. Both a and b will contain 10

• B. Both a and b will contain 20

• C. Both p and q will point to a

• D. Both p and q will point to b

Correct answer: D. Both p and q will point to b.

Place a = 10 at 0x1000 and b = 20 at 0x2000. Initially, p stores 0x1000 and q stores 0x2000. Assignment p = q copies 0x2000 into p without changing either integer. Both pointers then designate b; a remains 10 and b remains 20 unchanged.

Question 10 (RSSB 2022, Computer Science, BCI-Paper2)

*ptrdata is a pointer to a data type.

The expression *ptrdata++ is evaluated as (C++) –

• A. *(ptrdata++)

• B. (*ptrdata)++

• C. *(ptrdata)+

• D. Depends on compiler

Correct answer: A. *(ptrdata++).

Postfix ++ binds before unary *, so the parse is *(ptrdata++). Let ptrdata point to 7 at 0x1000, followed by 9 at 0x1004. The expression yields 7, then advances the pointer to 0x1004. It does not increment stored value 7, which would require (*ptrdata)++ instead.

C++ Data Types MCQs 11-12: pointer-to-pointer and reference traces

Question 11 (TCS 2026)

Predict the output of the following program:

#include<iostream>
using namespace std;
int main()
{
    const char* p = "12345";
    const char **q = &p;
    *q = "abcde";
    const char *s = ++p;
    p = "XYZWVU";
    cout << *++s;
    return 0;
}

• A. Compiler Error

• B. c

• C. b

• D. Garbage Value

Correct answer: B. c.

Because q points to p, *q = "abcde" redirects p to a. Then s = ++p advances p to b and copies that address to s. Redirecting p to "XYZWVU" leaves s unchanged. Finally, ++s advances from b to c, which is printed by the program.

Question 12 (TCS 2024)

Output of following C++ program?

#include <iostream>
using namespace std;
int main()
{
int x = 10;
int& ref = x;
ref = 20;
cout << "x = " << x << endl ;
x = 30;
cout << "ref = " << ref << endl;
return 0;
}

• A.

  x = 20
  ref = 30

• B.

  x = 20
  ref = 20

• C.

  x = 10
  ref = 30

• D.

  x = 30
  ref = 30

Correct answer: A. x = 20, then ref = 30.

A reference is an alias, not a copy. int& ref = x binds both names to one int. Thus ref = 20 changes x from 10 to 20, producing the first line. Then x = 30 changes the same object, so reading ref produces 30 on the second line.

C++ data types: diagnose the misses and choose the next step

Misses on Questions 1 to 3 call for reviewing fundamental types and literal syntax. For Questions 4 to 6, practise assumptions and conversions. For Questions 7 or 8, rewrite declarations one variable per line. For Questions 9 to 12, trace addresses and aliases first.

Redo all 12 tomorrow in 12 minutes: allow 2 minutes each for Questions 11 and 12, and 8 minutes for the other ten. Follow C++ Programming for a dedicated language sequence, Coding For Placements for a multi-language path, or browse Coding & Skills. Compare the type system with Data Types and Operators in C, then use C Programming MCQs if you also need C declaration practice.