Inputs, processes and outputs of an algorithm

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Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. In the line INPUT Mark, what part of the algorithm is this?

A An input: data is read into the algorithm

B An output: a result is shown to the user

2. Which statement is an OUTPUT in an algorithm?

A Total ← Total + 1

B OUTPUT Total

3. Which line is a process?

A Average ← Total / 5

B INPUT Total

4. Is IF Score >= 50 THEN a process or an input?

A An input: it reads the score from the user

B A process: it makes a decision

5. Where is a value kept while the algorithm uses it between input and output?

A In a variable or an array

B In an OUTPUT statement

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1INPUT Mark		AAn output: the algorithm displays a message and the value of Total to the user
2OUTPUT "Total: ", Total		BThis is a process (counting stored in a variable), not an output. Nothing is shown to the user until an OUTPUT statement such as OUTPUT Count runs.
3A process: a calculation that works on the input data and stores the result in a variable		CIF Mark >= 50 THEN
4A process: a decision that chooses what happens next depending on the input		DThis is a process (a calculation stored in a variable), not an input. The input is the INPUT Mark statement that brings the value in.
5Inputs: Total ← Total + Mark		ETotal ← Total + Mark
6Outputs: Count ← Count + 1		FAn input: the algorithm takes a value from the user and stores it in the variable Mark

Definitions

Input, process, output

Fill in the Blanks

Complete each line of code by filling in the missing parts.

_____ Price Total ← Price * 2 OUTPUT Total

INPUT Price INPUT Qty Total ← Price _ Qty

INPUT Mark __ Mark >= 50 THEN OUTPUT "Pass"

INPUT Age NextAge ← Age + 1 ______ NextAge

FOR Count ← 1 TO 3 INPUT Scores[_____] NEXT Count

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A INPUT Length

B INPUT Width

C Area = Length * Width

D OUTPUT Area

Question 2

A OUTPUT Mark

B IF Mark >= 50 THEN

C OUTPUT "Pass"

D ENDIF

Question 3

A INPUT Price

B INPUT Quantity

C Total ← Price * Qty

D OUTPUT Total

Question 4

A INPUT Cost

B Cost * 0.2 ← Tax

C Final ← Cost + Tax

D OUTPUT Final

Question 5

A DECLARE Marks : ARRAY[1:3] OF INTEGER

B FOR Count ← 1 TO 3

C INPUT Marks[Count]

D ENDFOR

E OUTPUT Marks[1]

Answer Key

Inputs, processes and outputs of an algorithm

Section A: Quick Questions

A — An input: data is read into the algorithm

B — OUTPUT Total

A — Average ← Total / 5

B — A process: it makes a decision

A — In a variable or an array

Section B: Match the Pairs

INPUT Mark → An input: the algorithm takes a value from the user and stores it in the variable Mark

OUTPUT "Total: ", Total → An output: the algorithm displays a message and the value of Total to the user

A process: a calculation that works on the input data and stores the result in a variable → Total ← Total + Mark

A process: a decision that chooses what happens next depending on the input → IF Mark >= 50 THEN

Inputs: Total ← Total + Mark → This is a process (a calculation stored in a variable), not an input. The input is the INPUT Mark statement that brings the value in.

Outputs: Count ← Count + 1 → This is a process (counting stored in a variable), not an output. Nothing is shown to the user until an OUTPUT statement such as OUTPUT Count runs.

Section C: Definitions

Input, process, output — Every algorithm takes INPUT data, carries out processes on it (calculations, decisions, storing in variables or arrays), then gives OUTPUT results.

Section D: Fill in the Blanks

INPUT Price
Total ← Price * 2
OUTPUT Total

INPUT Price
INPUT Qty
Total ← Price * Qty

INPUT Mark
IF Mark >= 50 THEN
  OUTPUT "Pass"

INPUT Age
NextAge ← Age + 1
OUTPUT NextAge

FOR Count ← 1 TO 3
  INPUT Scores[Count]
NEXT Count

Section E: Spot the Error

C — The calculation stores its result in a variable, so it needs the assignment arrow. It should be Area ← Length * Width. A single = is used for comparison.

A — The algorithm needs Mark as its input. Line 1 should be INPUT Mark so the value is read in, not OUTPUT Mark, which would display a value that does not exist yet.

C — Qty was never input or declared. The process must use the input variable Quantity: Total ← Price * Quantity.

B — The variable being assigned to must be on the left of the arrow and the calculation on the right. It should be Tax ← Cost * 0.2.

D — A FOR loop in IGCSE pseudocode ends with NEXT followed by the loop variable, so line 4 should be NEXT Count. ENDFOR is not a pseudocode keyword.