Lesson 2:

Under the hood

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Year 8 – Computing systems

Starter activity

Question .

What is the main task of a general-purpose computing system?

1. The main task is to execute programs.
2. There is no main task. It can perform any task prescribed by a program.
3. The main task depends on the system. Different systems may perform a different main task.
4. The main task depends on the user. Different users may need the system to perform a different main task.

Starter activity

A machine playing noughts and crosses

In the previous lesson,

a human executed a program for noughts and crosses.

Question What do you think it would take for a machine to be able to execute that program?

Starter activity

A machine playing noughts and crosses

In the previous lesson,

a human executed a program for noughts and crosses.

Question What do you think it would take for a machine to be able to execute that program?

It needs to ‘understand’ the program.

Language

It needs to ‘read’ the board and ‘write’ on it.

Input and output

Starter activity

A machine playing noughts and crosses

The physical components of a computing system are called hardware.

Hardware is any component of a computing system that you can touch.

The programs of a computing system are called software.

Objectives

Lesson 2: Under the hood

In this lesson, you will:

• Describe the hardware components used in computing systems and how they work together in order to execute programs
• Highlight how all computing systems, regardless of form, are similar in structure (‘architecture’)

Activity 1

Check the specs

Specifications or ‘specs’: a table of hardware components and technical characteristics

Your handout contains specs for a range of modern computing devices.

Question .

What are the components that are present in every one of these computing systems?

They must be important, right?

Activity 1

Check the specs – Answers

Activity 1

Check the specs – Answers

Answer . Computing systems need a processor, memory, and storage. Modern systems also rely heavily on communication between them.

Activity 1

Check the specs – Answers

Systems without input/output devices can connect to such devices. Input and output is always present in computing systems.

Activity 1

Insight

Diverse computing systems have strikingly similar components:

all computing systems are similar in structure (‘architecture’).

Let’s examine:

What the common components do

How they function together in order to execute programs

Activity 2

What does it do?

The storage (secondary memory) is the set of components that stores programs and data.

Storage is persistent: it retains its contents when the power is off.

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Question . Name a few common storage devices.

Answer . Hard disk drives (HDD), solid-state drives (SSD), USB flash drives or USB sticks, SD cards

Storage technology evolves over time.

The concept of storage is a constant.

Activity 2

What does it do?

The storage (secondary memory) is the set of components that stores programs and data.

Storage is persistent: it retains its contents when the power is off.

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Question . Name a few common storage devices.

Storage technology evolves over time.

The concept of storage is a constant.

Activity 2

What does it do?

The storage (secondary memory) is the set of components that stores programs and data.

Storage is persistent: it retains its contents when the power is off.

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storage

stores

Activity 2

What does it do?

The main memory is the component that stores the programs and data currently in use.

Memory is volatile: its contents are lost when the power is off.

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Terminology: The main memory is commonly referred to as RAM (random-access memory).

Activity 2

What does it do?

The main memory is the component that stores the programs and data currently in use.

Memory is volatile: its contents are lost when the power is off.

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How it works with other components

When a program must be executed,

it is loaded from storage in memory, along with the data required.

Any new or modified data must be saved from memory to storage.

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Terminology: The memory is commonly referred to as RAM (random-access memory).

Activity 2

What does it do?

The main memory is the component that stores the programs and data currently in use.

Memory is volatile: its contents are lost when the power is off.

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Terminology: The memory is commonly referred to as RAM (random-access memory).

storage

stores

Activity 2

What does it do?

The main memory is the component that stores the programs and data currently in use.

Memory is volatile: its contents are lost when the power is off.

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Terminology: The memory is commonly referred to as RAM (random-access memory).

saved into

storage

memory

programs

under execution

data

under processing

stores

stores

Activity 2

What does it do?

The processor is the component that executes program instructions.

An instruction may:

• Perform arithmetic or logic operations on data
• Perform input/output of data
• Control program flow

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Terminology: The processor is commonly referred to as the CPU (central processing unit).

Activity 2

What does it do?

The processor is the component that executes program instructions.

An instruction may:

• Perform arithmetic or logic operations on data
• Perform input/output of data
• Control program flow

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Terminology: The processor is commonly referred to as the CPU (central processing unit).

How it works with other components

Instructions are fetched one by one from memory into the processor, along with any required data.

The processor decodes and executes each instruction.

Any resulting data is moved into memory.

Activity 2

What does it do?

The processor is the component that executes program instructions.

An instruction may:

• Perform arithmetic or logic operations on data
• Perform input/output of data
• Control program flow

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Terminology: The processor is commonly referred to as the CPU (central processing unit).

memory

stores

Activity 2

What does it do?

The processor is the component that executes program instructions.

An instruction may:

• Perform arithmetic or logic operations on data
• Perform input/output of data
• Control program flow

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Terminology: The processor is commonly referred to as the CPU (central processing unit).

moved into

memory

processor

program instructions

resulting

data

stores

decodes

executes

generate

Activity 2

An analogy

Knitting patterns, yarn supplies, half-finished and finished projects are kept on the shelves.

This is the storage for programs and data.

Activity 2

An analogy

When the knitter works on a project, the knitting pattern and materials are transferred to the work area, where they can be kept handy for quick access.

This is the memory, where the program under execution is stored temporarily, along with the required data under processing.

Activity 2

An analogy

The knitter reads from the knitting pattern, one instruction at a time, and carries out the instruction, operating on the material at hand.

The knitter is the processor.

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Activity 2

What does it do?

Computing systems exchange information and form networks using communication components.

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Programs and data are transferred between computing systems, when required.

This allows:

• Input to be obtained remotely
• Data to be stored on remote systems
• Programs to be executed remotely

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Activity 2

What does it do?

Computing systems exchange information and form networks using communication components.

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storage

programs

data

stores

Activity 2

What does it do?

Computing systems exchange information and form networks using communication components.

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Question . Name different ways for computing systems to communicate.

Hint: Think about networks

Activity 2

What does it do?

Computing systems interact with the user and their surroundings through devices for input and output .

Input: data received by a system

Output: data transmitted from a system

transfer

user

memory

data

stores

surroundings

Activity 2

What does it do?

Computing systems interact with the user and their surroundings through devices for input and output .

Question . Name a few common input devices.

Input: data received by a system

Output: data transmitted from a system

Input and output devices evolve over time.

The concepts of input and output are constants.

Activity 2

What does it do?

Computing systems interact with the user and their surroundings through devices for input and output .

Question . Name a few common output devices.

Input: data received by a system

Output: data transmitted from a system

Input and output devices evolve over time.

The concepts of input and output are constants.

Plenary

Wearable computing

Google Glass is a wearable computing system. Use the worksheet to label its components.

Input

Output

Program execution

Program & data

(volatile storage)

Program & data (persistent storage)

Data exchange with other systems

Summary

In this lesson, you...

Next lesson, you will...

Explore how the processor, memory, and storage interact to execute programs in real scenarios

Define what an operating system is, and provide an overview of what it does

Described the hardware components used in computing systems and how they work together in order to execute programs

Highlighted how all computing systems, regardless of form, are similar in structure (‘architecture’)