IGCSE Computer Science Paper 2 Definitions Worksheet: 8.1b Sequence, Selection and Iteration and 8.1c Procedures and Functions (Modules 389–398)
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Key terms
Write what each term means, in your own words.
1
nested IF
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CASE OF ... IF ... ENDIF ... ENDCASE
3
IF inside a loop
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IF...THEN FOR...NEXT...ENDIF
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nested loop
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nesting
7
sequence, selection, iteration
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subroutine
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PROCEDURE
10
FUNCTION
Answer Key
IGCSE Computer Science Paper 2 · Modules 389–398 · Student wording will vary for definitions
1nested IF — An IF placed inside the THEN or ELSE branch of another IF. It is only checked when that outer branch runs, and each IF needs its own ENDIF, with the inner ENDIF written first.
2CASE OF ... IF ... ENDIF ... ENDCASE — A CASE clause can hold an IF, and an IF branch can hold a CASE. Close the inner structure first with its own ENDIF or ENDCASE, then close the outer one.
3IF inside a loop — An IF or CASE placed in a loop body is tested again on every repeat, so each pass can take a different branch depending on the current value.
4IF...THEN FOR...NEXT...ENDIF — A loop written inside an IF branch only runs when that branch is chosen. If the condition is FALSE, it is skipped. NEXT ends the loop first, then ENDIF ends the IF.
5nested loop — A loop placed inside another loop. The inner loop completes all its repeats for every single repeat of the outer loop, so a 3 by 4 nest runs the inner body 12 times.
6nesting — Putting one structure inside another, three levels deep. Indent each level and close them in reverse order: innermost first, e.g. ENDIF, ENDIF, then NEXT.
7sequence, selection, iteration — Set counters to 0 first (sequence), loop to read input (iteration), use IF inside the loop to pick values to count or total (selection), then OUTPUT the result after the loop.
8subroutine — A named block of code, written once, that runs whenever it is called. Procedures and functions are the two kinds, and they break a program into parts.
9PROCEDURE — A named subroutine that does a job, like outputting a line, but does not return a value. It is called as a full statement and can have parameters or none.
10FUNCTION — A named subroutine that returns a single value to the place where it is called, so the call can be used inside an expression, such as x ← Total(2, 3).