Checked and unchecked arithmetic in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the checked keyword do in C#?

The checked keyword forces the runtime to throw an OverflowException if an arithmetic operation exceeds the limits of the data type.

beginner

What happens when arithmetic overflow occurs inside an unchecked block?

The overflow is ignored and the result wraps around without throwing an exception.

intermediate

Give an example of when you might want to use checked arithmetic.

Use checked when you want to catch errors caused by values exceeding the limits, such as in financial calculations where accuracy is critical.

beginner

What is the default behavior of arithmetic overflow in C# if neither checked nor unchecked is specified?

By default, arithmetic overflow in C# does not throw an exception and behaves like unchecked, wrapping around silently.

intermediate

How can you apply checked or unchecked to a single expression?

You can wrap the expression inside checked(expression) or unchecked(expression) to control overflow checking for just that expression.

What exception does checked arithmetic throw on overflow?

A OverflowException

B NullReferenceException

C IndexOutOfRangeException

D DivideByZeroException

checked arithmetic throws OverflowException when the result exceeds the data type limits.

What is the default overflow behavior in C# if no keyword is used?

A Throws OverflowException

B Program crashes

C Throws NullReferenceException

D Wraps around silently

By default, overflow wraps around silently, like unchecked.

Which keyword forces overflow checking only for a specific expression?

A checked(expression)

B unchecked(expression)

C overflow(expression)

D safe(expression)

You can use checked(expression) to check overflow for just that expression.

When would you prefer unchecked arithmetic?

A When debugging errors

B When you want exceptions on overflow

C When performance is critical and overflow is acceptable

D When working with strings

unchecked avoids exceptions and can be faster when overflow is expected or acceptable.

Which of these is true about checked and unchecked blocks?

A <code>checked</code> disables overflow checking

B <code>checked</code> enables overflow exceptions

C <code>unchecked</code> enables overflow exceptions

D Both behave the same

checked enables overflow exceptions; unchecked disables them.

Explain the difference between checked and unchecked arithmetic in C#.

Think about what happens when numbers get too big.

Describe how to use checked and unchecked for controlling overflow in expressions and blocks.

Consider both whole blocks of code and single calculations.