Type modifiers in C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a type modifier in C++?

A type modifier changes the meaning of a basic data type to alter its size or behavior. Examples include signed, unsigned, long, and short.

beginner

What does the unsigned modifier do when applied to an integer type?

It makes the integer type store only non-negative values (zero and positive numbers), effectively doubling the maximum positive range by removing negative values.

beginner

How does the long modifier affect an integer type?

The long modifier increases the size of the integer type, allowing it to store larger numbers than the default int.

beginner

What is the difference between signed and unsigned modifiers?

signed allows storing both negative and positive numbers, while unsigned stores only zero and positive numbers.

intermediate

Can you combine multiple type modifiers? Give an example.

Yes, you can combine them. For example, unsigned long int means an integer type that is both unsigned and long, allowing only positive large numbers.

Which type modifier allows only non-negative integer values?

A short

B signed

C long

D unsigned

The unsigned modifier restricts the integer to non-negative values only.

What does the long modifier do to an integer type?

A Increases its size to store larger numbers

B Makes it store only negative numbers

C Decreases its size

D Changes it to a floating-point type

The long modifier increases the size of the integer type to hold larger values.

Which of these is a valid combination of type modifiers?

A signed float

B unsigned short int

C long double int

D unsigned char long

unsigned short int is valid. signed float and long double int are invalid combinations.

What is the default sign of an int if no modifier is specified?

A unsigned

B short

C signed

D long

By default, int is signed, meaning it can hold negative and positive values.

Which modifier would you use to store very large integer values?

A long

B unsigned

C short

D signed

The long modifier increases the size of the integer type to store larger values.

Explain what type modifiers are and list the common ones used with integer types in C++.

Think about how you can change the size or sign of numbers.

Describe how combining type modifiers affects the data type, giving an example.

Consider how two modifiers together change the range of values.

Practice

1. Which of the following type modifiers in C++ makes a variable value unchangeable after initialization?

easy

A. long

B. unsigned

C. volatile

D. const

Solution

1. Step 1: Understand the role of const

   The const modifier makes a variable's value fixed after it is set.

2. Step 2: Compare with other modifiers

   unsigned changes number sign, volatile affects optimization, long changes size, but none prevent value change.

3. Final Answer:

   const -> Option D

4. Quick Check:

   const = unchangeable value [OK]

Hint: const means value cannot be changed after set [OK]

Common Mistakes:

• Confusing const with unsigned
• Thinking volatile prevents changes
• Assuming long affects constness

2. Which of the following declarations correctly uses the unsigned modifier for an integer variable named count?

easy

A. unsigned count int;

B. count unsigned int;

C. unsigned int count;

D. int count unsigned;

Solution

1. Step 1: Recall correct syntax for unsigned int

   The correct order is unsigned int followed by the variable name.

2. Step 2: Check each option

   unsigned count int; invalid order; count unsigned int; places variable before type, invalid; unsigned int count; correct; int count unsigned; invalid.

3. Final Answer:

   unsigned int count; -> Option C

4. Quick Check:

   unsigned int before variable name [OK]

Hint: Put unsigned before int and then variable name [OK]

Common Mistakes:

• Placing unsigned after variable name
• Mixing order of type and modifier
• Using invalid syntax like unsigned count int

3. What is the output of the following C++ code?

unsigned int x = 10;
int y = -5;
if (x + y > 5)
    std::cout << "True";
else
    std::cout << "False";

medium

A. True

B. False

C. Compilation error

D. Undefined behavior

Solution

1. Step 1: Understand unsigned and signed addition

   Adding signed -5 to unsigned 10: -5 promotes to unsigned (large value, e.g., 4294967291u on 32-bit).

2. Step 2: Calculate the result and compare

   10u + 4294967291u = 4294967286u (wraps around mod 2^32). 4294967286u > 5u is true, so prints "True".

3. Final Answer:

   True -> Option A

4. Quick Check:

   unsigned + negative int promotes and wraps to large unsigned > 5 true [OK]

Hint: Mixing unsigned + signed negative promotes and wraps around [OK]

Common Mistakes:

• Assuming -5 stays negative (ignores promotion)
• Expecting True (ignores wraparound)
• Thinking this causes compile error

4. Identify the error in this code snippet:

const int x;
x = 5;

medium

A. Missing initialization of const variable

B. Incorrect use of int type

C. Assignment operator is wrong

D. No error, code is correct

Solution

1. Step 1: Check const variable initialization rules

   A const variable must be initialized when declared.

2. Step 2: Analyze the code

   Here, const int x; is declared without initialization, then assigned later, which is invalid.

3. Final Answer:

   Missing initialization of const variable -> Option A

4. Quick Check:

   const must be initialized immediately [OK]

Hint: const variables need immediate initialization [OK]

Common Mistakes:

• Trying to assign const after declaration
• Ignoring initialization requirement
• Thinking assignment operator is wrong

5. You want to store a large positive number that can never be negative and might exceed 2 billion. Which type modifier combination is best for the variable score?

hard

A. const int score;

B. unsigned long score;

C. short unsigned score;

D. volatile int score;

Solution

1. Step 1: Understand the data requirements

   We need a large positive number, no negatives, possibly > 2 billion.

2. Step 2: Match type modifiers to needs

   unsigned ensures no negatives; long increases size to hold large values; const fixes value; short limits size; volatile affects optimization, not size.

3. Step 3: Choose best option

   unsigned long fits the need best.

4. Final Answer:

   unsigned long score; -> Option B

5. Quick Check:

   unsigned long = large positive number [OK]

Hint: Use unsigned long for large positive numbers [OK]

Common Mistakes:

• Choosing const which fixes value
• Using short which limits size
• Using volatile which doesn't affect size