L3 Compilers & Interpreters for Translation

Key Terms

• Translator – A program that turns source code into machine code.

• Compiler – Translates the whole program at once into machine code.

• Interpreter – Translates and runs the program line by line.

• Syntax Error – A mistake in your code that breaks the rules of the language.

Why Do We Need Translators?

Your Python code (source code) looks easy to read:

print("Hello")

But the computer’s CPU only understands 1s and 0s (machine code). A translator helps convert the code into something the computer can run.

What is a Compiler?

A compiler looks at your entire program, checks it, and then translates all of it into machine code before running anything.

Example: You write a 50-line Python program. The compiler checks all the lines and then makes one file that can run.

Pros:

• Faster once compiled

• No need for Python to be installed to run the compiled file

Cons:

• If there’s even one error, the program won’t run

• Takes longer to test small changes

What is an Interpreter?

An interpreter runs the program one line at a time. If it finds a mistake, it stops right there.

Example: You write:

print("Start")

print(5 + "x")

print("End")

The interpreter will run the first line, then crash on the second line.

Pros:

• Great for testing and debugging

• Easier to find errors line by line

Cons:

• Slower to run the whole program

• Needs the interpreter installed to run the code

Comparing Compiler and Interpreter

Real-Life Context

Think of a compiler like a bakery baking all cookies before the shop opens—they’re ready to sell fast. An interpreter is like making cookies one by one as people order them—it’s slower, but easier to fix if something goes wrong.

Common Mistakes to Avoid

🚫 Mistake: Thinking both do the same thing. 

✅ Tip: Use an interpreter (like Python) when you’re learning and testing. Use a compiler for finished software you want to share.