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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

  • Describe the central processing unit including its role
  • Describe internal memory, i.e. ROM and RAM and the differences between them
  • Define input and output devices and describe the difference between them
  • Define secondary/backing storage

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

Describe the central processing unit including its role

  • The CPU is the 'brain' of the computer.

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  • It is where all the searching, sorting, calculating

and decision making takes place.

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  • The speed of the CPU is measured in Gigahertz

(GHz).

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  • A 1 GHz CPU can carry out 1 billion instructions per

second!

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  • Intel and AMD are the most popular CPU brands.

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

Main Memory

The CPU will again check the Cache for the next piece of data. This time the CPU will be able to get the data from the Cache Memory.

Applications are installed in the Secondary Storage (Hard drive).

​

Temporary data from Applications in use are held in the Main Memory.

The CPU will first check the Cache for the required piece of the data so that it can be processed.

If the data is not in the cache then the CPU will check the RAM and transfer data to the CPU.

The Cache will then transfer the next piece of data from the RAM into Cache.

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

Main Memory

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

Cache

  • Cache is the fastest type of Memory.

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  • It is located between the processor and the RAM.

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  • Cache collects data from the RAM.

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  • Holds onto commonly used data.

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  • The Cache will automatically transfer the next set of data from the RAM in to the Cache so that it can be processed by the CPU.

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

RAM (Random Access Memory)

  • RAM stands for Random Access Memory

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  • RAM is the part of the computer that temporarily stores the instructions that the computer is running whilst the data is being processed by the CPU.

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  • RAM is volatile which means that when the computer is turned off all data is lost

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

ROM (Read Only Memory)

  • ROM stands for Read Only Memory

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  • ROM is a built in memory that can not be changed (Read Only).

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  • ROM normally holds the ‘boot up’ instructions to start the computer – without it the computer wouldn’t know what to do when on button is switched on (e.g. the operating system will not start).

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  • ROM is non-volatile memory which means that memory is not lost when computer is turned off.

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

Describe the difference between the Cache, RAM & ROM?

Exam Question

Cache

Fastest, CPU, Common Data

RAM

Temporary data, volatile (data

lost on startup)

ROM (Read only memory)

Read Only, Bootup & Non-

volatile (Data not lost)

The Cache memory is the fastest type of memory. It is located between the CPU and RAM. It holds commonly used data. RAM (Random Access Memory) is a volatile type of memory which means all data is lost on startup. In contrast ROM (Read Only Memory) is non-volatile which means data is not lost on startup. The ROM memory

boot up

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is Read Only and contains instructions. The RAM memory hold

temporary

data which is processed by the CPU.

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

Input and Output devices

Devices need to be connected to a computer to allow data to be inputted and outputted.

​

The general name for these extra devices is ‘peripheral devices’. They are usually

categorised into input devices, output devices and storage devices.

Input

Output

Storage

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​

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An input device is a device that can pass date into the computer

Devices that take data from the computer are known as output devices.

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

Define secondary/backing storage

Backing storage is also known as secondary storage

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Backing storage is non-volatile which means that

data is not lost when computer is turned off.

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Backing storage is used to store data for a long time (data can be read from and written to)

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Users tend to make copies of original files on backing storage.

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ICT IGCSE Theory – Revision Presentation

1.2 The Main Components of Computer Systems

Chapter 1: Types and components of computer systems

Exam Question

Describe what is backing storage (secondary storage)? Key Words: non-volatile, data, long time, Read, Write & copies

non-volatile

Backing storage also known as secondary storage is which means that

data

is not lost when computer is turned off. An example of backing storage is a fixed hard

Data

drive. is stored for a long time and can be accessed at any point (Read and write).

Users tend to make copies of original files on backing storage.

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