IGCSE Computer Science Paper 2 Definitions Worksheet: 8.1b Sequence, Selection and Iteration (Modules 369–378)
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Key terms
Write what each term means, in your own words.
1
IF condition THEN ... ENDIF
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ELSE
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IF Age >= 13 AND Age <= 19 THEN
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ELSE IF
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CASE OF Choice
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OTHERWISE
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1 TO 9 :
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CASE OF
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FOR Count <- 1 TO 10
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FOR Count <- 10 TO 1 STEP -1
Answer Key
IGCSE Computer Science Paper 2 · Modules 369–378 · Student wording will vary for definitions
1IF condition THEN ... ENDIF — Runs the indented statements only when the condition is TRUE. If it is FALSE they are skipped. ENDIF closes the selection and lines up with IF.
2ELSE — Adds a second branch that runs when the IF condition is FALSE, so exactly one of the two branches runs. ELSE has no condition of its own and lines up with its IF.
3IF Age >= 13 AND Age <= 19 THEN — A compound condition joins tests with AND, OR or NOT so one IF checks several things at once. AND needs both tests true; OR needs at least one true.
4ELSE IF — A nested IF placed inside ELSE to choose between 3+ alternatives. Conditions are tested in order, only one branch runs, and every IF needs its own ENDIF.
5CASE OF Choice — Compares one variable (here Choice) with a list of values, runs the statement beside the matching value, and is closed by ENDCASE.
6OTHERWISE — The last clause of a CASE statement. It runs when the variable matches none of the listed values, e.g. OTHERWISE : OUTPUT "Invalid choice". Without it, nothing happens if no value matches.
71 TO 9 : — In a CASE clause, value1 TO value2 matches a whole range, such as 1 TO 9. Indented statements under the clause all run. Ranges in one CASE must not overlap.
8CASE OF — Use CASE OF when one variable is matched against fixed values, like a menu choice. Use IF when you test conditions with <, > or AND/OR, like age or score tests.
9FOR Count <- 1 TO 10 — A count-controlled loop that repeats the indented lines end - start + 1 times, adding 1 to the counter each time. It is closed by NEXT Count, which names the same counter.
10FOR Count <- 10 TO 1 STEP -1 — STEP sets how much the FOR counter changes each repeat. Without STEP the counter goes up by 1. A negative STEP, such as -1, makes the counter count down.