Comments with // (7c)

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Which line is a correct pseudocode comment?

A // Add the marks together

B Add the marks together //

2. What does a comment do when the algorithm is run?

A Nothing - it only explains the code to the reader

B It changes the value of a variable

3. Where can a comment go?

A On its own line above the code it explains

B Only at the very end of the program

4. Which line has a short comment at the end of a line correctly?

A Total ← Total + Mark Add mark to total //

B Total ← Total + Mark // Add mark to total

5. A comment needs 3 lines of explanation. How should it be written?

A Put // on the first line only

B Start every line with //

Match the Pairs

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

Left column		Right column
1// Add the mark to the total		AThe explanation has no // at the start, so it is not marked as a comment and looks like part of the code. It should be: Count ← Count + 1 // Add one to the count
2Total ← Total + Mark // running total		B// Check if the student passed IF Mark >= 50 THEN
3A comment that needs several lines must start each line with //		CThe comment on the second line is fine, but the last line ends with an empty //, which explains nothing. Also the comment lines should describe each statement. Remove the empty // or write a useful comment such as // Show the total
4A comment starts with // and explains the code without being part of the algorithm		DA short comment at the end of a line, explaining that statement without changing it
5Count ← Count + 1 Add one to the count		E// Calculate the average // of the three test marks
6// Read the mark // and add it to Total Input Mark Total ← Total + Mark OUTPUT Total //		FA comment on its own line above the code, explaining what the next statement does

Definitions

Fill in the Blanks

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

__ Ask the user for their age INPUT Age

Total ← 0 __ Start the total at zero

// Add the three marks together __ then divide by three to find the mean Average ← Total / 3

__ Repeat for each of the five students FOR Count ← 1 TO 5 INPUT Mark NEXT Count

OUTPUT Total __ Show the final total

Spot the Error

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

Question 1

A // Double the price

B DECLARE Total : REAL

C Total ← Price * 2 # doubled

D OUTPUT Total

Question 2

A INPUT Age

B / Check for an adult

C IF Age >= 18 THEN

D OUTPUT "Adult"

E ENDIF

Question 3

A DECLARE Total : INTEGER

B Total ← Mark1 + Mark2 + Mark3

C // Divide total by 3 to find

D the average mark

E Average ← Total / 3

Question 4

A Total ← 0

B FOR Count ← 1 TO 5

C // INPUT Num // read it

D Total ← Total + Num

E NEXT Count

Question 5

A /* Area of a rectangle */

B INPUT Length

C INPUT Width

D OUTPUT Length * Width

Answer Key

Comments with // (7c)

Section A: Quick Questions

A — // Add the marks together

A — Nothing - it only explains the code to the reader

A — On its own line above the code it explains

B — Total ← Total + Mark // Add mark to total

B — Start every line with //

Section B: Match the Pairs

// Add the mark to the total → A comment on its own line above the code, explaining what the next statement does

Total ← Total + Mark // running total → A short comment at the end of a line, explaining that statement without changing it

A comment that needs several lines must start each line with // → // Calculate the average // of the three test marks

A comment starts with // and explains the code without being part of the algorithm → // Check if the student passed IF Mark >= 50 THEN

Count ← Count + 1 Add one to the count → The explanation has no // at the start, so it is not marked as a comment and looks like part of the code. It should be: Count ← Count + 1 // Add one to the count

// Read the mark // and add it to Total Input Mark Total ← Total + Mark OUTPUT Total // → The comment on the second line is fine, but the last line ends with an empty //, which explains nothing. Also the comment lines should describe each statement. Remove the empty // or write a useful comment such as // Show the total

Section C: Definitions

// — Starts a comment that runs to the end of the line. It explains the code to the reader but is not part of the algorithm, so it is ignored when run.

Section D: Fill in the Blanks

// Ask the user for their age
INPUT Age

Total ← 0 // Start the total at zero

// Add the three marks together
// then divide by three to find the mean
Average ← Total / 3

// Repeat for each of the five students
FOR Count ← 1 TO 5
  INPUT Mark
NEXT Count

OUTPUT Total // Show the final total

Section E: Spot the Error

C — Pseudocode comments start with //, not #. The line should be Total ← Price * 2 // doubled.

B — A comment needs two slashes. A single / is not a comment. The line should be // Check for an adult.

D — A comment that runs over several lines needs // at the start of every line. The second line is missing its //, so it should be // the average mark.

C — The // at the start of the line turns the whole statement into a comment, so the number is never input. The line should be INPUT Num // read it.

A — /* ... */ is not the pseudocode comment style. A comment starts with //, so the line should be // Area of a rectangle.