Writing an algorithm in pseudocode from a problem

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Quick Questions

Shade in the A or B circle for each question.

1. A problem says: 'Input two numbers and output their total.' Which line should come first in your algorithm?

A OUTPUT Total

B DECLARE Num1, Num2, Total : INTEGER

2. Which is the correct order for writing an algorithm from a problem?

A DECLARE, INPUT, process, OUTPUT

B OUTPUT, process, INPUT, DECLARE

3. A problem says: 'Output 'Pass' if the mark is 50 or more, otherwise output 'Fail'.' Which structure fits?

A FOR ... TO ... NEXT

B IF ... THEN ... ELSE ... ENDIF

4. A problem says: 'Input 30 test marks and output the total.' Which structure should you choose for the process?

A A FOR loop that repeats 30 times

B A CASE statement with 30 branches

5. A problem says: 'Input a menu choice of 1, 2 or 3 and output a different message for each.' Which structure is the neatest choice?

A CASE Choice OF ... ENDCASE

B REPEAT ... UNTIL Choice = 3

Match the Pairs

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

Left column		Right column
1DECLARE Total : INTEGER		AFOR Count ← 1 TO 5 INPUT Score NEXT Count
2INPUT Mark IF Mark >= 50 THEN OUTPUT "Pass" ENDIF		BThe statements are in the wrong order and the IF is incomplete. The IF must come before the OUTPUT, wrap it, and end with ENDIF.
3The problem has several fixed choices for one value, so a CASE structure suits the process step		CDeclare the variable and its data type at the start, before it is used in the algorithm
4The problem says to repeat an action a set number of times, so a FOR loop is used for the process step		DInput a value, process it with a selection test from the problem, then output the result
5Total ← 0 INPUT Mark Total ← Total + Mark		EThe variables Total and Mark are used but never declared. DECLARE Total : INTEGER and DECLARE Mark : INTEGER must come first.
6INPUT Age OUTPUT "Adult" IF Age >= 18 THEN		FCASE OF Choice 1 : OUTPUT "Start" 2 : OUTPUT "Quit" ENDCASE

Definitions

DECLARE, INPUT, process, OUTPUT

Fill in the Blanks

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

_______ Mark : INTEGER INPUT Mark OUTPUT Mark

DECLARE Age : INTEGER _____ Age OUTPUT Age

IF Mark >= 50 THEN OUTPUT "Pass" _____

FOR Count ← 1 TO 5 INPUT Score ____ Count

DECLARE Total : INTEGER Total ← 0 ______ Total

Spot the Error

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

Question 1

A DECLARE Num1 : INTEGER

B DECLARE Num2 INTEGER

C INPUT Num1

D INPUT Num2

E OUTPUT Num1 + Num2

Question 2

A DECLARE Mark : INTEGER

B INPUT Mark

C IF Mark > 50 THEN

D OUTPUT "Pass"

E ENDIF

Question 3

A DECLARE Total : INTEGER

B DECLARE Num : INTEGER

C Total ← 1

D INPUT Num

E Total ← Total + Num

F OUTPUT Total

Question 4

A DECLARE Choice : INTEGER

B INPUT Choice

C CASE OF Choice

D 1 OUTPUT "Start"

E OTHERWISE : OUTPUT "Stop"

F ENDCASE

Question 5

A DECLARE Price : STRING

B DECLARE Total : REAL

C INPUT Price

D Total ← Price * 3

E OUTPUT Total

Answer Key

Writing an algorithm in pseudocode from a problem

Section A: Quick Questions

B — DECLARE Num1, Num2, Total : INTEGER

A — DECLARE, INPUT, process, OUTPUT

B — IF ... THEN ... ELSE ... ENDIF

A — A FOR loop that repeats 30 times

A — CASE Choice OF ... ENDCASE

Section B: Match the Pairs

DECLARE Total : INTEGER → Declare the variable and its data type at the start, before it is used in the algorithm

INPUT Mark IF Mark >= 50 THEN OUTPUT "Pass" ENDIF → Input a value, process it with a selection test from the problem, then output the result

The problem has several fixed choices for one value, so a CASE structure suits the process step → CASE OF Choice 1 : OUTPUT "Start" 2 : OUTPUT "Quit" ENDCASE

The problem says to repeat an action a set number of times, so a FOR loop is used for the process step → FOR Count ← 1 TO 5 INPUT Score NEXT Count

Total ← 0 INPUT Mark Total ← Total + Mark → The variables Total and Mark are used but never declared. DECLARE Total : INTEGER and DECLARE Mark : INTEGER must come first.

INPUT Age OUTPUT "Adult" IF Age >= 18 THEN → The statements are in the wrong order and the IF is incomplete. The IF must come before the OUTPUT, wrap it, and end with ENDIF.

Section C: Definitions

DECLARE, INPUT, process, OUTPUT — To write an algorithm from a problem, DECLARE variables first, then INPUT, process with IF, CASE or a loop, then OUTPUT. Check each part against the problem and use the exam format.

Section D: Fill in the Blanks

DECLARE Mark : INTEGER
INPUT Mark
OUTPUT Mark

DECLARE Age : INTEGER
INPUT Age
OUTPUT Age

IF Mark >= 50 THEN
  OUTPUT "Pass"
ENDIF

FOR Count ← 1 TO 5
  INPUT Score
NEXT Count

DECLARE Total : INTEGER
Total ← 0
OUTPUT Total

Section E: Spot the Error

B — A DECLARE statement needs a colon between the identifier and the data type. It should be DECLARE Num2 : INTEGER.

C — The problem says a mark of 50 or more passes, but > leaves out a mark of exactly 50. The condition should be Mark >= 50.

C — A running total must be set to 0 before anything is added, otherwise the answer is wrong by 1. It should be Total ← 0.

D — Each CASE branch needs a colon between the value and the statement. It should be 1 : OUTPUT "Start".

A — Price is used in a calculation and can have decimals, so it must be REAL. A STRING cannot be multiplied. It should be DECLARE Price : REAL.