Char type and Unicode behavior in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of char and Unicode code point conversion

What is the output of this C# code snippet?

C Sharp (C#)

char ch = '\u0041';
int code = ch;
Console.WriteLine(code);

A 65

B 41

C A

D Syntax error

💡 Hint

Remember that '\u0041' is a Unicode escape for a character, and casting char to int gives its code point.

The character '\u0041' is 'A'. Its Unicode code point is 65. Casting char to int returns this numeric value.

❓ Predict Output

intermediate

Output of char arithmetic with Unicode characters

What does this C# code print?

C Sharp (C#)

char ch = 'A';
ch = (char)(ch + 2);
Console.WriteLine(ch);

A B

B C

C D

D Runtime error

💡 Hint

Adding 2 to 'A' moves two characters forward in Unicode.

The character 'A' has code 65. Adding 2 gives 67, which is 'C'.

❓ Predict Output

advanced

Output when using surrogate pairs in char arrays

What is the output of this C# code?

C Sharp (C#)

string s = "\U0001F600"; // Unicode emoji 😀
Console.WriteLine(s.Length);

A 2

B 1

C 4

D 0

💡 Hint

Some Unicode characters use two char units called surrogate pairs in .NET strings.

The emoji 😀 is represented by two UTF-16 code units, so Length is 2.

❓ Predict Output

advanced

Behavior of char.IsSurrogate method

What does this C# code print?

C Sharp (C#)

char high = '\uD83D';
char low = '\uDE00';
Console.WriteLine(char.IsSurrogate(high));
Console.WriteLine(char.IsSurrogate(low));

A False\nFalse

B True\nFalse

C True\nTrue

D False\nTrue

💡 Hint

Both high and low surrogate halves are considered surrogate chars.

Both '\uD83D' and '\uDE00' are surrogate code units, so IsSurrogate returns true for both.

🧠 Conceptual

expert

Understanding char and Unicode code points in C#

Which statement about C# char type and Unicode is TRUE?

A The char type can store any Unicode character without needing surrogate pairs.

B A char represents a full Unicode code point, including those outside the Basic Multilingual Plane.

C C# strings store Unicode code points directly as 32-bit integers.

D A char is a 16-bit value representing a UTF-16 code unit, which may be a surrogate half for some characters.

💡 Hint

Think about how UTF-16 encoding works and how C# char relates to it.

C# char is a 16-bit UTF-16 code unit. Characters outside the Basic Multilingual Plane use two chars (surrogate pairs).

Practice

1. What does the char type in C# represent?

easy

A. A single Unicode character enclosed in single quotes

B. A string of characters enclosed in double quotes

C. An integer number representing ASCII code

D. A floating-point number representing character code

Solution

1. Step 1: Understand the char type

   The char type stores exactly one character, not multiple characters or numbers.

2. Step 2: Recognize the syntax for char

   In C#, a char is written with single quotes, like 'A', representing a Unicode character.

3. Final Answer:

   A single Unicode character enclosed in single quotes -> Option A

4. Quick Check:

   char = single Unicode character [OK]

Hint: Remember: char holds one character in single quotes [OK]

Common Mistakes:

• Confusing char with string type
• Thinking char stores numbers directly
• Using double quotes for char

2. Which of the following is the correct way to declare a char variable with the letter 'Z' in C#?

easy

A. char letter = "Z";

B. char letter = Z;

C. char letter = 'Z';

D. char letter = (char)"Z";

Solution

1. Step 1: Check the syntax for char declaration

   In C#, a char must be assigned a single character enclosed in single quotes.

2. Step 2: Evaluate each option

   char letter = "Z"; uses double quotes which is for strings, char letter = Z; misses quotes, char letter = (char)"Z"; tries casting a string which is invalid.

3. Final Answer:

   char letter = 'Z'; -> Option C

4. Quick Check:

   Single quotes for char = char letter = 'Z'; [OK]

Hint: Use single quotes for char, double quotes for string [OK]

Common Mistakes:

• Using double quotes instead of single quotes
• Assigning char without quotes
• Casting string to char incorrectly

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

char c = 'A';
int code = c;
Console.WriteLine(code);

medium

A. Syntax error

B. A

C. 0

D. 65

Solution

1. Step 1: Understand char to int conversion

   Assigning a char to an int converts the character to its Unicode numeric value.

2. Step 2: Find Unicode value of 'A'

   The Unicode (and ASCII) value of 'A' is 65, so code becomes 65.

3. Final Answer:

   65 -> Option D

4. Quick Check:

   char 'A' to int = 65 [OK]

Hint: Casting char to int gives Unicode number [OK]

Common Mistakes:

• Expecting character 'A' to print instead of number
• Thinking char stores ASCII only, not Unicode
• Assuming syntax error on implicit conversion

4. Identify the error in this code snippet:

char c = "B";
int code = (int)c;
Console.WriteLine(code);

medium

A. Cannot convert string to char using double quotes

B. Casting char to int is invalid

C. Missing semicolon after declaration

D. Console.WriteLine cannot print integers

Solution

1. Step 1: Check char assignment syntax

   Assigning a char requires single quotes, but double quotes were used, which is a string.

2. Step 2: Validate other parts

   Casting char to int is valid, semicolons are present, and Console.WriteLine can print integers.

3. Final Answer:

   Cannot convert string to char using double quotes -> Option A

4. Quick Check:

   char needs single quotes, not double [OK]

Hint: Use single quotes for char, double quotes cause error [OK]

Common Mistakes:

• Using double quotes for char
• Thinking casting char to int is wrong
• Ignoring syntax errors in assignment

5. Given the code below, what will be the output?

char c1 = '\u03A9'; // Greek capital letter Omega
char c2 = 'Ω';
Console.WriteLine(c1 == c2);

hard

A. Compilation error

B. True

C. False

D. Runtime exception

Solution

1. Step 1: Understand Unicode escape and character literal

   \u03A9 is the Unicode escape for Greek capital Omega, same as the character 'Ω'.

2. Step 2: Compare the two chars

   Both c1 and c2 represent the same Unicode character, so the comparison returns true.

3. Final Answer:

   True -> Option B

4. Quick Check:

   Unicode escape equals character literal = True [OK]

Hint: Unicode escape and char literal can represent same character [OK]

Common Mistakes:

• Assuming escape and literal differ
• Expecting false due to different syntax
• Thinking Unicode escape causes error