What does null-terminated string mean in C?

It means the character array ends with a special null character (\0) that marks the end of the text data for functions like printf and strlen.

How is a .NET string different from a null-terminated C string?

A .NET string stores the length of the text explicitly and supports Unicode, while a C string is a series of characters followed by a null terminator.

What is a Null-Terminated String? | FullStackPrep.Dev

💡 Concept Name

Null-Terminated String – A sequence of characters in memory that ends with a special null character ('\0'), used by C and C++ to mark where a string finishes.

📘 Quick Intro

In C, text is stored as an array of characters, but the language needs a way to know when the text stops. That’s why every C string ends with the '\0' (null) character. This null-terminator signals the end of the string so functions don’t read past the real data.

🧠 Analogy / Short Story

Imagine a row of parked cars in a garage, but there’s no line to mark the end. Now, add a big “STOP” sign after the last car—the null character acts as this stop sign, telling everyone: “this is where the row ends.”

🔧 Technical Explanation

💡 The last element of a C string array is always '\0' (ASCII code 0).
🔍 String functions like strlen, printf("%s"), and strcpy scan characters until they hit '\0'.
⚠️ If you forget the null terminator, programs may read garbage data or even crash due to buffer overruns.
🖥️ This approach is specific to C/C++. Other languages like .NET or Java store the string’s length instead.
🌐 .NET strings are not null-terminated—they use a length prefix and Unicode encoding for safety and flexibility.

🎯 Purpose & Use Case

✅ Used in C programming for text processing and system-level code.
✅ Fundamental for many operating system APIs and embedded firmware.
✅ Still relevant when interoping between C/C++ and higher-level languages.

💻 Real Code Example

// Null-terminated string in C
#include <stdio.h>

int main() {
    char language[] = "C Programming"; // Automatically null-terminated
    printf("%s\n", language);          // Output: C Programming
    return 0;
}

❓ Interview Q&A

Q1: How do you know a string ends in C?
A: It ends with a null character ('\0').

Q2: What’s the risk if a string isn’t null-terminated?
A: String functions may keep reading memory until a random zero is found, leading to bugs or security issues.

Q3: Do .NET strings use null-termination?
A: No, .NET strings store length internally and support Unicode.

Q4: Why does C use null-terminated strings instead of storing the length?
A: To save memory and keep things simple for low-level operations (at the cost of safety and efficiency).

Q5: How do you print a null-terminated string in C?
A: Use printf("%s", stringVariable) and C will print up to the null character.

Q6: Can null-terminated strings cause security vulnerabilities?
A: Yes, missing null terminators can lead to buffer overflows.

Q7: How does .NET avoid buffer overflows with strings?
A: By storing string length separately, it avoids reading beyond the string.

Q8: What is a downside of null-terminated strings?
A: Functions must scan for the null terminator, which can be inefficient.

Q9: Are C strings Unicode by default?
A: No, C strings are arrays of bytes, typically ASCII or platform dependent.

Q10: How do you safely handle strings in C to avoid errors?
A: Always ensure the string is properly null-terminated and buffer sizes are checked.

📝 MCQs

Q1. Which character ends a C string?

\0 (null)
\n (newline)
EOF
Space

Q2. Which language depends on null-terminated strings?

Python
C
C#
Java

Q3. How does .NET store string length?

Null-terminated
Fixed size
Length-prefixed
Double nulls

Q4. What can happen if null-terminator is missing?

Faster code
Buffer overflow or garbage read
Shorter string
No effect

Q5. Is null-termination safe for Unicode?

Yes
No, can cause errors
Only in Linux
Only with ASCII

Q6. What is the risk of not null-terminating a C string?

Performance gain
Security vulnerabilities
No risk
Compilation error

Q7. How do .NET strings represent characters?

ASCII
UTF-8
UTF-16 encoding
ISO-8859-1

Q8. Why does C use null-terminated strings?

Speed
Memory saving and simplicity
Unicode support
Thread safety

Q9. How do you print a C string safely?

Use puts() only
Ensure null termination before using printf
Use cout instead
Use strcpy()

Q10. What is a downside of null-terminated strings?

Memory overhead
Potential buffer overflows
Fixed string length
Unicode limitation

💡 Bonus Insight

Many bugs in C come from mishandled null-terminated strings—always double-check that you have a '\0' at the end before passing strings to low-level APIs!

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What is a Null-Terminated String?