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Computer Science: All Topics
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Edexcel IGCSE Computer Science
Computer Science: All TopicsComplete deck
01·1.1 Algorithms
What is an algorithm?
Answer
A finite, ordered set of unambiguous instructions for solving a problem or completing a task.
02·1.1 Algorithms
Why are algorithms used in computer science?
Answer
They describe the logical steps needed to process inputs and produce required outputs; those steps can be implemented in a program.
03·1.1 Algorithms
What are four ways to represent an algorithm?
Answer
A written description, a flowchart, pseudocode or program code.
04·1.1 Algorithms
What is pseudocode?
Answer
A structured, code-like description of an algorithm that is not tied to a specific programming language.
05·1.1 Algorithms
What is a flowchart?
Answer
A diagram showing the steps, decisions and direction of control flow in an algorithm using standard symbols and arrows.
06·1.1 Algorithms
Which flowchart shape represents START or END?
Answer
A terminator: an oval or rounded-ended shape.
07·1.1 Algorithms
Which flowchart shape represents a processing step?
Answer
A rectangle, for an operation such as SET Total TO Price * Quantity.
08·1.1 Algorithms
Which flowchart shape represents a decision?
Answer
A diamond, with branches identified by conditions such as YES and NO.
09·1.1 Algorithms
Which flowchart shape represents input or output?
Answer
A parallelogram, for input from a keyboard or output to a display.
10·1.1 Algorithms
What do arrows represent in a flowchart?
Answer
The direction of control flow between algorithm steps.
11·1.1 Algorithms
Which flowchart symbol indicates a subprocess?
Answer
A rectangle with extra vertical lines at its left and right sides, representing a subprocess defined separately.
12·1.1 Algorithms
Why must instructions in an algorithm be unambiguous?
Answer
Each instruction must have one clear interpretation so a computer or a person following it knows exactly what action to take.
13·1.1 Algorithms
How does an algorithm differ from a program?
Answer
An algorithm describes the solution steps; a program implements the algorithm using the syntax of a programming language.
14·1.1 Algorithms
Why might a programmer choose a flowchart before writing code?
Answer
It makes control flow and the different decision paths easy to visualise and check before implementation.
15·1.1 Algorithms
Why might a programmer prefer pseudocode over a flowchart?
Answer
Pseudocode presents complex steps compactly in a form that can be translated into high-level program code.
16·1.1 Algorithms
Interpret: RECEIVE Length FROM (INTEGER) KEYBOARD. What happens?
Answer
An integer is read from the keyboard and assigned to the variable Length.
17·1.1 Algorithms
Interpret: SEND Price * 2 TO DISPLAY when Price = 7. What is displayed?
Answer
14; the expression is evaluated before its result is displayed.
18·1.1 Algorithms
What does SET Score TO Score + 1 mean in Pearson pseudocode?
Answer
Assign Score its previous value plus 1, thereby incrementing it by one.
19·1.1 Algorithms
What is the purpose of the ampersand (&) operator in Pearson pseudocode?
Answer
It appends/concatenates values in data structures; for strings it joins text, coercing a non-string value to text when needed.
20·1.1 Algorithms
A flowchart contains START → INPUT age → decision age >= 18 → YES: display Adult; NO: display Minor → END. What does it do?
Answer
It classifies the entered age as Adult when age is at least 18 and Minor otherwise.
21·1.1 Algorithms
Interpret: SET Scores TO [6, 9, 3]; SEND Scores[1] TO DISPLAY. What is output?
Answer
9, because Pearson arrays use zero-based indexing: Scores[0] = 6 and Scores[1] = 9.
22·1.1 Algorithms
Which description is clearer for a computer algorithm: “wait until hot” or “WHILE Temperature < 80 DO ... END WHILE”, and why?
Answer
The explicit temperature condition is clearer: it gives a measurable stopping rule rather than an ambiguous judgment of “hot”.
23·1.1 Algorithms
What is sequence in an algorithm?
Answer
Instructions executed one after another in their specified order.
24·1.1 Algorithms
What is selection in an algorithm?
Answer
Choosing which instruction or branch to execute according to a condition.
25·1.1 Algorithms
What is iteration in an algorithm?
Answer
Repeating a block of instructions while or until a condition is met, or for a specified number of repetitions.
26·1.1 Algorithms
Which Pearson pseudocode command assigns a value to a variable?
Answer
SET variable TO value, for example SET Count TO 0.
27·1.1 Algorithms
Which Pearson pseudocode command displays output?
Answer
SEND expression TO DISPLAY, for example SEND Total TO DISPLAY.
28·1.1 Algorithms
Which Pearson pseudocode command reads an integer from the keyboard?
Answer
RECEIVE Number FROM (INTEGER) KEYBOARD.
29·1.1 Algorithms
Which pseudocode construct selects between two alternatives?
Answer
IF condition THEN ... ELSE ... END IF.
30·1.1 Algorithms
Which pseudocode loop checks its condition before the body?
Answer
WHILE condition DO ... END WHILE; the loop body may execute zero times.