IGCSE Computer Science Paper 2 Definitions Worksheet: 7c Pseudocode and Flowcharts (Modules 216–231)
Name:
Date:
Class:
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Key terms
Write what each term means, in your own words.
1
for i in range(1, n + 1):
2
while True:
3
scores[i - 1]
4
purpose
5
Input, process, output
6
trace table
7
Tracing a loop
8
dry run
9
Describe the processes
10
Describing a loop
Answer Key
IGCSE Computer Science Paper 2 · Modules 216–231 · Student wording will vary for definitions
1for i in range(1, n + 1): — Python for FOR i ← 1 TO n. range() stops before its end value, so use n + 1 to include n. A third argument is the STEP; a negative step counts down.
2while True: — Python's version of REPEAT ... UNTIL: the body runs at least once, then an if with break at the end stops the loop when the UNTIL condition is True.
3scores[i - 1] — A pseudocode array starting at index 1 becomes a Python list starting at 0, so element Scores[i] is written scores[i - 1] in Python.
4purpose — What the whole algorithm achieves, stated in one sentence, such as 'finds the largest of ten numbers'. It is not a line-by-line description. Check the OUTPUT and identifier names for clues.
5Input, process, output — Every algorithm takes INPUT data, carries out processes on it (calculations, decisions, storing in variables or arrays), then gives OUTPUT results.
6trace table — A table used to dry-run pseudocode: one column per variable plus OUTPUT, and a new row each time a statement changes a value. INPUT values come from the question.
7Tracing a loop — Work through the loop body once per pass, recording changed values in a new row each time. Test the condition before the body for WHILE and after it for REPEAT. Check the final row.
8dry run — Running an algorithm by hand with test values, then comparing the inputs with the final outputs to work out its purpose, such as totalling, counting or finding the largest.
9Describe the processes — State, in order and in plain words, what each part of the algorithm does with the data: set up variables, what the loop repeats, what the decision does, then the output.
10Describing a loop — State how many times the loop repeats or the condition it stops on, and what happens to the data each time round, e.g. each mark is added to Total.