Readable programs

Courses GCSE Computer Science Python Coding Readable programs

Why Layout Matters

Edexcel Paper 2 marks programs that other people can follow. Use indentation for blocks, white space around operators, and meaningful identifiers such as total_score instead of x.

Add short comments where the intent is not obvious from the names. A comment should say why, not repeat the code. Layout, names and comments do not change the answer the CPU computes, but they change how fast a human can find a logic error.

A meaningful identifier is a name that

{"answers": {"A": "Describes what the variable or subprogram is for", "B": "Is always a single letter", "C": "Must be written in CAPITALS", "D": "Is ignored by the interpreter"}, "question_text": "A meaningful identifier is a name that", "correct_answer": "A"}

Comments versus Identifiers

Identifier

minutes_left = 10 already tells you the unit. You do not need a comment that says “this is minutes”.

Comment

Use a comment for a non-obvious choice, such as why a loop stops at 59 rather than 60. If you rename a variable, update comments that mention the old name.

Use [[indentation]] for blocks and [[meaningful]] names such as total_score instead of x.

{"cloze_text": "Use [[indentation]] for blocks and [[meaningful]] names such as total_score instead of x."}

{"keyword": "meaningful identifier", "definition": "A variable, constant or subprogram name that describes its purpose"}

Question Type: fill in the blanks

{"paragraph": "Comments should explain [[why]] something is done, not copy the [[code]] line by line."}

Question Type: short answer

{"answer": "Indentation/white space, meaningful identifiers, or comments.", "rubric": {"0": "Incorrect or no response", "1": "Partial credit", "2": "Indentation/white space, meaningful identifiers, or comments."}, "question": "Name two techniques that make a program easier to maintain."}