Cambridge IGCSE Computer Science 0478: Command words and keywords

Cambridge IGCSE Computer Science (0478) uses the standard Cambridge command words. The syllabus also defines pseudocode keywords and conventions that must be followed in algorithm questions. Any subject-specific command words are listed in the syllabus—check the 2023–2025 or 2026–2028 version for your exam series.

Command words in Computer Science 0478

Command word	What to do in Computer Science	Common mistake
State	Short answer; one point per mark	Overwriting
Identify	Choose from code/diagram/data	Adding explanation
Define	Precise computing meaning	Vague or everyday language
Describe	What the code/process does; no “why”	Adding explanation
Explain	Why or how; use “because”	Only describing
Suggest	Apply to context; propose solution	Generic answer
Compare	Similarities and differences	Listing separately
Analyse	Break down; show relationships	Only describing
Evaluate	Judge; conclude with evidence	No conclusion
Outline	Main points only	Too much detail
Sketch	Simple diagram; key features	Too detailed
Write	Produce pseudocode/algorithm	Wrong syntax
Trace	Follow through step by step	Missing steps
Calculate	Work out; show working	Wrong formula

Pseudocode and algorithm questions

For Write or algorithm questions, follow the Cambridge pseudocode guide exactly. Keywords, data types and structure matter. Wrong syntax can lose marks even if the logic is correct.

Pseudocode keywords (syllabus)

Data types

Keyword	Use correctly	Avoid
INTEGER	Whole numbers	REAL for integers
REAL	Numbers with decimal part	INTEGER for decimals
CHAR	Single character	STRING
STRING	Sequence of characters	CHAR
BOOLEAN	TRUE or FALSE	”Yes/No” or 1/0

Control structures

Keyword	Use correctly	Avoid
IF … THEN … ELSE	Conditional	Wrong structure
CASE … OF	Multiple selection	Nested IF when CASE better
REPEAT … UNTIL	Post-condition loop	WHILE when REPEAT needed
WHILE … DO	Pre-condition loop	REPEAT when WHILE needed
FOR … TO … STEP	Count-controlled loop	Wrong loop type
ENDPROCEDURE	End of procedure	Missing or wrong
ENDFUNCTION	End of function	Missing or wrong

Input/output

Keyword	Use correctly	Avoid
INPUT	Read from user	READ (not in syllabus)
OUTPUT	Print to screen	PRINT (check syllabus)
GET	Read from file	INPUT (different)
PUT	Write to file	OUTPUT (different)

Pseudocode conventions

• Keywords in UPPER CASE (e.g. IF, REPEAT, PROCEDURE)
• Identifiers in Pascal case (e.g. NumberOfPlayers)
• Indentation by four spaces for nested statements
• Comments preceded by //
• Meta-variables in angled brackets < >
• Statements one per line; numbered if required

Computing keywords examiners look for

Programming concepts

Term	Use correctly	Avoid
Algorithm	Step-by-step solution	”Code”
Pseudocode	Language-independent design	”Code”
Variable	Named storage; value can change	”Box”
Constant	Named storage; value fixed	Variable
Array	Collection of same type	List (Python term)
Procedure	Named block; no return value	Function
Function	Named block; returns value	Procedure
Parameter	Input to procedure/function	”Input”
Return value	Value sent back by function	Output
Iteration	Repeating (loop)	“Loop” (acceptable but iteration preferred)
Selection	Choosing path (IF/CASE)	“If”
Sequence	Steps in order	”Order”

Hardware and software

Term	Use correctly	Avoid
CPU	Central Processing Unit	”Processor”
RAM	Random Access Memory; volatile	ROM
ROM	Read-Only Memory; non-volatile	RAM
Secondary storage	Hard drive, SSD, USB	”Memory”
Operating system	Software managing hardware	”Windows” (example, not definition)
Compiler	Translates whole program	Interpreter
Interpreter	Translates line by line	Compiler
Binary	Base 2	”Off/on”
Hexadecimal	Base 16	”Hex” (acceptable)
Boolean	TRUE/FALSE	”Yes/No”
AND, OR, NOT	Logic operators	Wrong logic

Data and security

Term	Use correctly	Avoid
Bit	Binary digit; 0 or 1	”Digit”
Byte	8 bits	”8 bits” (acceptable)
Character set	Mapping of characters to numbers	”Font”
ASCII	American Standard Code	Unicode (different)
Encryption	Scrambling data for security	”Password”
Validation	Check data is reasonable	Verification
Verification	Check data is correct (e.g. re-enter)	Validation
Decomposition	Breaking problem into sub-problems	”Splitting”
Abstraction	Hiding unnecessary detail	”Simplifying”

What examiner reports say

• Pseudocode—follow the syllabus guide exactly; wrong syntax loses marks.
• Trace—show every step; one error can cascade.
• Describe vs Explain—Describe = what; Explain = why/how.
• Suggest—apply to the scenario; generic answers score poorly.
• Define—precise computing definitions; avoid vague language.

Tips for Computer Science 0478

1. Learn the pseudocode guide—keywords, structure, conventions.
2. Use correct data types—INTEGER, REAL, STRING, CHAR, BOOLEAN.
3. Indent correctly—nested structures need clear indentation.
4. Trace carefully—show each step; check initial values.
5. Define precisely—e.g. “An algorithm is a step-by-step procedure to solve a problem.”
6. Past papers + mark schemes show acceptable pseudocode.

How Tutopiya helps

Tutopiya supports Computer Science 0478 with tutors who use the pseudocode guide and past papers. Explore IGCSE resources or book a free trial.

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Based on Cambridge IGCSE Computer Science 0478 syllabus and pseudocode guide. Check the latest syllabus for your exam series.