Dissecting Pseudocode

• ICT
• Secondary Education

Pseudocode

Objective

1. To be familiar with the data types in pseudocode.
2. To revise the function of Sequence
3. To write a Sequence pseudocode

Data Types in Pseudocode

String

The String data type is used for data that can be used to store a number of letters, digits and symbols.

"...."

String

When assigning data to a string it should be placed within quotes e.g. name = "Dave"

Strings

Strings are printable, Mathematical operations cannot be performed on strings even if they only contain numbers.

e.g. if you have the following code:

x = "7" 

y = "3"

OUTPUT x + y

The result that is output for the user would be "73" NOT 10. This is known as concatenation, 2 or more strings can be joined together using the + symbol.

Integer

An Integer can be used to store a positive whole number (No decimals numbers)

You'll see this in Exams as Int

REAL

The Real data type will allow you to store decimal numbers (Positive or negative) e.g. Cost = 5.50

​Real data can be used in mathematical operations

CHAR

The Char data type can be used to store one single character.

​e.g. Gender = "M"

BOOLEAN

The Boolean data type can have only two possible values, these are TRUE or FALSE.

​E.g. Accepted = true

Any questions on Data Types for Pseudocode?

Sequence

Sequence refers to

1. code or sections of code that run line by line, in sequential order without deviation.
2. code that repeats a certain number of times.

Question 1

Write a SEQUENCE pseudocode to instruct a user to input their age and name.

Make sure to use OUTPUT,INPUT, and don't forget to use "..." for sentences

SEQUENCE Syntax Instructions in IGCSE

INPUT - prompting your user to put in text or numbers. 

"..." - Strings marks or quotation marks is to indicate the TEXT ONLY sentences in your pseudocode.

OUTPUT/PRINT - To display or show the outcome instructions.

Write a SEQUENCE pseudocode to instruct a user to input their age and name.

Make sure to use OUTPUT,INPUT, and don't forget to use "..." for sentences

Objective

1. To be familiar with the data types in pseudocode.
2. To revise the function of Sequence
3. To write a Sequence pseudocode

Objective

1. To revise the function of Selection
2. To write a IF pseudocode
3. To write a CASE pseudocode

In programming, the term selection means

1. that the program can choose to run different commands based on a condition being true or false.
2. follows a set of instructions that with the order it is given.
3. code that repeats a certain number of times.

Write a pseudocode to instruct a user to input their age and name. If then person is older than 18 then your pseudocode should allow the person input their address and telephone number, else you have to let them know they are too young to drive.

IF and Case - Selection

Create a CASE pseudocode that shows 3 different fruits and their pricing. Output an error message if the user did not select 3 of the options.

Theory Questions

Explain the difference between the programming concepts of sequence and selection.

Include an example of a programming statement for each concept in your explanation (4m)

Objectives

1.  To revise on the function of IF statement.

2. To practice on the function of CASE statement.

3. To distinguish the function between Sequence and Selection.

Objectives

1.  To revise on Selection.

2. To define Iteration 

3. To practise writing FOR...TO...NEXT

A programmer wants to test that the readings from 2000 electricity meters are greater than 400 units and less than 900 units.

Explain, using programming statements, how selection could be used n this program. (2m)

IF... THEN... ELSE... ENDIF is one type of conditional statement used when writing pseudocode

Identify and describe another type of conditional statement that you could use when writing pseudocode. Give a reason why you would use this type of conditional statement.

(4M)

Objectives

1. To revise on Iteration

2. To define Iteration 

3. To practise writing FOR...TO...NEXT

Iteration means

1. that the program can choose to run different commands based on a condition being true or false.
2. it does nothing
3. to repeat something over and over like a loop
4. follows a sequence order

Types of Iteration

For loop

While loop

Repeat until loop

For loop is used when

1. code needs to be repeated a specified number of times
2. will repeat forever while a set condition is true. also known as pre-condition loops.
3. will repeat forever UNTIL a condition becomes true. also known as a Post-condition loop.

Objective

1. Revise on Iteration

2. Practise a few iteration questions

Bob opens his business for 7 days. Create a For loop to calculate the total money made for the 7 days.

WHILE LOOPS

While loops are also known as pre-condition loops. This is because a while loop will repeat forever WHILE a set condition is true. This condition is checked at the start of the loop hence the name "pre-condition".

While loops are particularly useful when you do not know specifically how many times you want the code to repeat.

Example Uses

• A user should be able to use a program as many times as they like until they choose to quit
  
• A dice game will allow the user to roll the dice until they choose to quit
  
• A program should repeat forever (No way for the condition to be false)
  
• Validating a user input e.g. not accepting a password if it is less than 8 characters long.

REPEAT UNTIL LOOPS

A REPEAT UNTIL loop is also known as a Post-condition loop. This type of loop will repeat forever UNTIL a condition becomes true.

REPEAT...UNTIL is one type of loop structure.

Identify and describe TWO other types of loop structure that you could use when writing pseudocode.

What are the two loop structures? Describe them.

Objective

1. Revise on Iteration
2. Practice on For Loops
3. Practice on While Loops
4. Practive on Repeat Loops

Describe the purpose of each statement in this algorithm.

For X <- 1 TO 300
INPUT NAME
NEXT X

Explanation

The instructions requires 300 loops to input Names at each round.

Create a loop, that Input 10 numbers and print out their total

Input some numbers and calculate their total, stop when the total is greater than 20.

An algorithm has been written in pseudocode to input 100 numbers and print out the sum. A REPEAT...UNTIL lopp has been used.

Find the error in the pseudocode and suggest a correction

Rewrite the correct algorithm using a more suitable loop structure.