High-level vs low-level languages

Programming languages sit on different levels:

• High-level languages (e.g. Python, Java) — close to human language, easy to read/write and portable across machines. Must be translated before running.
• Low-level languages — close to the hardware. This includes machine code (binary, 1s and 0s — the only language the CPU runs directly) and assembly language (mnemonics like ADD, LDA that map to machine code).

Trade-off: high-level = easier for humans & portable; low-level = harder to write but gives fine control and can be more efficient/faster.

Which level?

Machine code & assembly language

Two low-level forms:

• Machine code — instructions as binary (0s and 1s). Runs directly on the CPU but is extremely hard for humans to write.
• Assembly language — uses short mnemonics (e.g. ADD, SUB, LDA, STA) instead of binary. Easier than machine code but still specific to a processor. It is turned into machine code by an assembler (one-to-one).

Nail it: assembly is a low-level language translated by an assembler; it is one step above raw machine code.

Translators: compiler, interpreter & assembler

A translator converts source code into machine code. Three types:

• Compiler — translates the whole program at once into machine code before it runs, creating an executable. Fast to run afterwards; errors are reported all together at the end.
• Interpreter — translates and runs the program one line at a time. Great for finding errors as you go, but slower to run and needs the interpreter each time.
• Assembler — translates assembly language into machine code (one-to-one).

Compiler vs interpreter: a compiler translates the whole program in one go; an interpreter translates line by line as it runs.

Which translator?

Language or translator?

Tap an item, then tap what it is.

The Integrated Development Environment (IDE)

An IDE is software that gives programmers all the tools they need in one place:

• Editor — where you write code, with features like syntax highlighting, auto-complete and auto-indent.
• Error diagnostics / debugger — helps find and fix bugs (e.g. breakpoints, step-through, showing variable values).
• Run-time environment — lets you run/test the program from within the IDE.
• Translator — a built-in compiler/interpreter to turn your code into machine code.

Why use an IDE: it speeds up writing, testing and debugging by combining the editor, translator, run-time environment and error tools in one program.

Which IDE feature?

Compiler benefit

Match tool to its job

Tap a term on the left, then its matching job on the right.

The big ideas to know

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