Lesson Objective

To learn how to use if else statements to make alternative decisions

Success Criteria

  • I know about booleans
  • I know about negation
  • I know about ‘not equal to’
  • I know how to use selection for strings
  • I know about the if else patterns
  • I know how to use the if else pattern in a Go program

Key Vocabulary

  • if
  • else
  • else if
  • selection
  • true
  • false
  • boolean
  • negation
  • negate
  • bool
  • comparison
  • program flow

Period of Study

KS2 Emerging

Co2/1.1 design, write and debug programs that accomplish specific goals, including controlling or simulating physical systems; solve problems by decomposing them into smaller parts

Co2/1.2 use sequence, selection, and repetition in programs; work with variables and various forms of input and output

Co2/1.3 use logical reasoning to explain how some simple algorithms work and to detect and correct errors in algorithms and programs

Maths - The pupils must have covered less than, less than or equal to, greater than, greater than or equal to, equal to and not equal to for numeric values. This is a prelude to full blown boolean algebra.

History of Science/Maths - See the wikipedia entry for George Boole, who invented boolean algebra. See also the Wikipedia entry for Claude Shannon, the father of information theory: Shannon’s master’s thesis showed how Boole’s idea from 100 years before could be put to practical use to solve any numeric or logical question, a discovery which opened the field of digital electronics.

SMSC

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Resources/Homework

The pupils will need to have Go installed on the school computers. They will also need a text editor installed. For Windows/MacOS X and Linux they should install Atom. For RaspberryPi they should install liteIDE. See the install guides on the website for more details.

The simpleio package needs to be downloaded and installed on the pupils computers.

The random package needs to be downloaded and installed on the pupils computers.

Both packages are required to run the timesquestion program.

Prerequisites

The example program uses the times tables up to 12, so the pupils must be familiar with these.

The lesson builds on earlier lessons so the pupils should have covered Lessons 1-8 in the series

Starter Activity

Show the pupils the compassion operators. Can they remember what each operator does? Can the pupils remember what is special about the question that an if statement asks? Can the pupils remember the rules for the if pattern?

Main teaching points

  • Introduce booleans and show that the result of an comparison can be assigned to a boolean type.
  • Introduce the idea of negation i.e. true is the opposite of false
  • Introduce the negation and not equals to operator
  • Show selection used with strings
  • Show the if else patterns
  • Explain the timesquestion Go program

For High Achievers

The pupils should understand that a boolean value represents true and false.

The pupils should understand that the result of a comparison operator is a boolean and can be assigned to a variable.

The pupils should understand that negation reverses the value of a boolean -> true becomes false and false becomes true.

The pupils should recognise and understand the negation and not equals operators.

The pupils should be able to use all if comparison operators with strings.

The pupils should recognise and understand the if else pattern.

The pupils should be able to enter the timesquestion program and run it without support.

For Middle Achievers

The pupils should understand that a boolean value represents true and false.

The pupils should understand that the result of a comparison operator is a boolean and can be assigned to a variable.

The pupils should understand that negation reverses the value of a boolean -> true becomes false and false becomes true with support.

The pupils should recognise and understand the negation and not equals operators with support.

The pupils should be able to use all if the comparison operators with strings with support.

The pupils should recognise and understand the if else pattern with support.

The pupils should be able to enter the timesquestion program and run it without support.

For Low Achievers

The pupils should understand that a boolean value represents true and false.

The pupils should understand that the result of a comparison operator is a boolean and can be assigned to a variable.

The pupils should understand that negation reverses the value of a boolean -> true becomes false and false becomes true with considerable support.

The pupils should recognise and understand the negation and not equals operators with considerable support.

The pupils should be able to use all if the comparison operators with strings with considerable support.

The pupils should recognise and understand the if else pattern with considerable support.

The pupils should be able to enter the timesquestion program and run it with support.

Plenary

The plenary asks the pupils to think (or guess) at what repetition is used for. Repetition is the subject of the next lesson. At the minute, the only way to run the program again is to run it from the start. There is no way to repeat just part of the program - the part that asks the question and then checks the answer. We will show them how to do this next.

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