Selection

What is selection?

Selection is the programming structure through which a computer executes one or other set of instructions according to whether a particular condition is met. You can build selection into a sequence of instructions. This ability to do different things, depending on what happens as a program is running, makes programming a powerful tool. At the core of many educational games is a simple selection command: if the answer is right then give a reward, otherwise (else) say the answer is wrong. Selection statements can be “nested” inside one another, allowing more-complex sets of conditions to be used to determine what happens in a program.

An example of how selection can be used to start a script in Scratch.

An example of how selection can be used to start a script in Scratch.

Nested selection and repetition commands in Scratch, to model a clock.

Nested selection and repetition commands in Scratch, to model a clock.

Why is selection important?

In computer science, selection gives us the capacity to write programs that are interactive, responding to inputs and behaving differently each time they run. Selection is integral to programs controlling physical systems. With automatic sliding doors, if an input from the motion sensor above the doors is detected then the doors open, else they stay shut. With burglar alarms, if motion is detected then a siren sounds, else it remains on standby. Electric ovens heat to a desired temperature, thanks to selection within the control program: if the oven temperature is the same as the demand temperature, the oven stops heating up – else, it keeps heating.

What does selection look like in the Primary curriculum?

Selection in programming is referenced in the Key Stage 2 objective “use selection in programs.” However, prior to this, younger pupils develop an understanding of selection in the world around them. For example, EYFS pupils might see examples of selection in the rules of their environment: “If there are fewer than two people in the roleplay area then enter, else choose another activity.” Similarly, they see examples of selection in everyday language and the choices we make: “If it’s cold out I’ll wear my woolly hat, else I won’t.” Some programming languages aimed at Key Stage 1 offer simple selection commands. As pupils progress through Key Stage 2, they use increasingly complex forms of selection commands and even consider combining (nesting) these to achieve a required result. In addition, the conditions which the selection blocks use will become more complex. This might initially be the simple comparison of a single answer, but subsequently progress to several
variable values and the use of AND or OR operators. As pupils progress through Key Stage 2 and gain more experience using selection commands, they should have confidence in identifying, whilst planning an algorithm, which commands to use, and structure it accordingly.

3 - 5 years

Younger pupils often use selection statements: for example, “If you do not give me that toy, I will tell the teacher!” However, when it comes to computing, their experience of selection is limited. Simple programmable toys such as Bee-Bots provide no means at all by which pupils can incorporate selection, the focus instead being on adding commands in simple sequences. When controlling a friend as a ‘human robot’, a child might instruct them to open a door. “If the door is closed then open the door” is the implication here, but it’s unlikely to be explicitly stated in this detailed way.

5 - 7 years

As with Early Years, pupils’ experience of selection is limited because the focus within programming is to understand sequence. However, children may be introduced to selection when using graphical programming apps. In ScratchJr, code can be executed if a sprite is touched. Using Daisy the Dinosaur, the “when” command executes code if a stated condition is met.

Two images showing conditional commands in ScratchJr and Daisy the Dinosaur.

The left image shows that ScratchJr's "when sprite touched" command can be used to execute code. The right image shows that Daisy the Dinosaur's "when" selection command can be used to execute code if the condition is met (here, that the iPad screen is touched).

7 - 11 years

Pupils aged 7–11 should have the opportunity to design, write and debug programs that use selection to accomplish specific goals. In doing so, they will have to design the algorithms for these programs, indicating how and where selection will be used. Ideally, this should be across different programming languages, such as Kodu and Scratch. They may have the opportunity to first tinker with selection commands, to develop an understanding of how these function, before moving on to more-purposeful programming. In any given context, they should think about the conditions upon which to base selection statements, and the commands they’ll trigger.

Selection enabling keyboard inputs to control sprite positions in a Scratch program.

Selection enabling keyboard inputs to control the position of a sprite in a Scratch program.

In Kodu, an object’s behaviour in a game is determined by a set of conditions – for example: when the left arrow is pressed, the object will move left. Similarly, interactions with other objects, variables and environments are programmed as a set of “when, do” conditions. An example is: “When I bump the apple, do eat it and add two points to my score.”

A screenshot of Kodu programming incorporating selection.

Selection in Kodu.

Find out more about selection / Downloads

Computing At School / Naace (2013): “Computing in the national curriculum – a guide for Primary teachers” (opens in a new window)

Wikibooks article on selection (opens in a new window)

Scratch wiki article on IF… THEN command (opens in a new window)

Scratch wiki article on IF…THEN…ELSE command (opens in a new window)

BBC Bitesize on sequence, selection and repetition (opens in a new window)

Activities that are great to get you started:

These activities develop pupils' understanding of selection.

Scratch Maths Quiz Selection

Age:7-11 years
Concepts / Approaches: Debugging, Collaborating, Selection, Programming
Curriculum Links: Maths

Pupils create a maths quiz in Scratch and learn about selection which, in this activity, allows the flow of the program to be altered depending on the player’s answers to questions. Initially pupils will use an ‘If… then…’ selection command, before moving on to using an ‘If…then… else…’ command.