Compiler vs Interpreter

Compiler vs Interpreter is one of the most common Compiler Design interview and viva questions. It is asked because it quickly checks whether you understand how high-level programs are executed.

What is a Compiler?

A compiler translates the full source code into machine code or target code before execution starts.

Examples:

• C
• C++
• Go

What is an Interpreter?

An interpreter translates and executes the program line by line during runtime.

Examples:

• Python
• JavaScript
• Ruby

Compiler vs Interpreter Table

| Feature | Compiler | Interpreter | | --- | --- | --- | | Translation | Full program at once | Line by line | | Error reporting | Often after full compilation | Usually during execution | | Speed | Faster execution | Slower execution | | Output | Produces target code/executable | No separate target program in basic form | | Debugging | Less immediate | More immediate |

Simple Example

If a program has 100 lines:

• a compiler checks and translates the whole program first
• an interpreter runs one line, then the next, during execution

Why compiled programs are faster

Because the translation work is already done before running the program.

Why interpreters are useful

Because they:

• make testing easier
• allow quick debugging
• support rapid development

Interview-style answer

A compiler translates the complete program before execution and usually produces target code, while an interpreter translates and executes the program line by line. Compiled programs are usually faster, while interpreted execution is more flexible for debugging and scripting.

Quick Revision Points

• compiler = full translation first
• interpreter = line-by-line execution
• compiler output runs faster
• interpreter is easier for quick testing

Viva Questions

1. What is a compiler?
2. What is an interpreter?
3. What is the difference between compiler and interpreter?
4. Why are compiled programs faster?
5. Give examples of compiled and interpreted languages.