IGCSE Computer Science Hardware

What are the 4 components of a computer

input, output, processing, storage

What is the purpose of the CPU

it processes the data and controls the flow of data between the computer's other units

Von Neumann Architecture

This is when data and instructions are stored in the same memory (RAM) in binary as a stored program.

The Control Unit

Component of a processor that directs and coordinates most of the operations in the computer.

And decodes instruction

Arithmetic Logic Unit (ALU)

The part of the central processing unit that performs arithmetic computations and logical operations.

Registers

Small, high-speed storage locations that temporarily hold data and instructions.

Program Counter (PC)

The register that contains the address of the next instruction to be executed

Memory Address Register (MAR)

Holds memory address for data or a instruction about to be used by the CPU

Memory Data Register (MDR)

holds the data that is being transferred either to or from the memory unit

Current Instruction Register (CIR)

holds the instruction currently being executed or decoded

Accumulator (ACC)

holds the result of an instruction before it is transferred to memory

CPU architecture
Unit 3 Computer architecture and

Fetch-Decode-Execute Cycle

The process that the CPU uses to retrieve and execute instructions

Buses

Collection of wires that carry signals between various components of the computer system

The three buses that make up the system bus are

The Address Bus, The Data Bus, The control Bus

The Address Bus

transfers addresses from the CPU to memory

Data Bus

transmits data from the CPU to memory or input/output controllers

Control Bus

transfers control signals from the control unit to other components in the computer system such as memory or input/output controllers

Memory Unit (MU)

Store's instructions and processes that the computer needs regularly while processing

Random Access Memory (RAM)

Temporary memory a computer uses to store information while it is processing.

What are the 3 factors that affect a CPU's performance

Clock Speed, CPU cores, Cache

Cores

The Number of Processing units

Cache

A component that is faster than the ram, but slower than the Registers

Clock Speed

Cycles per second measured in hertz

Instruction Sets

A set are commands and operations that the central processing unit can process.

Opcodes

Gives the CPU a precise job to happen

Operands

The actual data required for a specific job

What is an embedded system?

a computer implemented as part of a larger system.

What is an input device?

Device that inputs data into the computer

keyboard

An input device that enters data with letters, numbers, symbols, and special function keys.

optical mouse

uses optical sensors that emit and sense light to detect the mouse's movement

What is a microphone?

An audio input device that allows a user to enter sounds into the computer system.

What is a touch screen?

A special type of screen which reacts to human touch.

What are the types of touch screens

Resistive, Capacitative, infra red

What is an automatic input device

A device that functions on little to none human reaction

Examples of automatic input devices

Sensors, scanners, digital cameras

What is a sensor

An input device that takes readings from the environment such as temperate or light.

What is a barcode

A series of dark and light parallel lines of varying thickness

What are QR codes?

a type of 2D code that is used to provide easy access to info through a smart phone

What is an output device?

a device that outputs data from the computer

Examples of output devices

Monitors, touch screens, projectors, printers, speakers, actuator

What is the the difference between memory and storage

Memory is the microchips and transistors that the computer needs to operate,

Storage refers to the device used to store documents and files

Primary Storage

The main storage area in a computer where data is stored for quick access by the CPU.

magnetic hard drive

A hard drive consisting of

(Platters) Circular metal plates covered in a magnetic material
A electromagnetic read write head
A spindle
A track and sector

How is a HDD written into

The hard drive spins the metal disk(s) at a high speed using a motor
A read/write arm, controlled by an actuator, moves the head over the surface of the disc to the location of the data
The data is read/written using electromagnets

Solid State Hard Drive

Very fast storage drive with no moving parts. Faster than traditional spinning hard drive. Currently more expensive.

What is a flash drive

A collective term used to refer to any drive (typically usb) that uses flash technology

Optical Drives

A drive that is used to read disc drives

What is virtual memory?

a portion of the hard disk designated to function as additional RAM

what are Network interface Cards

A component used in computers to give them the ability to connect to the internet wired or wirelessly

What is a Mac Address

is a unique number stored in each NIC so it can be used to identify a device on a network.

What is an IP address?

a unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network.

What is a character set

All the characters and symbols that can be represented by a computer system where Each character and symbol is assigned a unique value;

What is sample resolution

Number of bits per sample

What is the sample rate

the number of samples taken per second

Define resolution

the number of pixels in the image

What is colour depth?

the number of bits used to represent each colour

serial simplex

Data is transmitted one bit at a time in a single direction on one wire

Serial-Half-duplex

Data can be transmitted in both directions on a single wire but only one bit at a time can be transmitted in one direction at a time

Serial-Full-duplex

Data can be transmitted in both directions at the same time on a single wire one bit at a time

Parallel-Simplex

Multiple wires transmit one bit at a time in one direction

Parallel-Half-duplex

Multiple wires send multiple bits of data in both directions but only one direction at a time

Parallel-Full-duplex

Multiple wires send multiple bits of data in both directions at the same time

Advantages of serial data transmission

The data will arrive in the order it is sent
It is less likely to have errors
Serial transmission is cheap over short and long distances as the cost of wire is fairly inexpensive

Disadvantages of serial

Data transmission is slow, especially over long distances as only small quantities of data can be transmitted at a time
Serial transmission is expensive over very long distances as the cost of wire dramatically increases

Advantages of parallel

Parallel transmission is fast as large quantities of data can be transmitted at any one time

Disadvantages of parallel

transmission is expensive over short distances as multiple wires need to be purchased. Transmission is very expensive over long distances as the cost of wires dramatically increases with the distance

How are packets transfered

Data is broken/split/divided into packets
Each packet (could) take a different route
A router controls the route/path a packet takes
... selecting the shortest/fastest available route/path
Packets may arrive out of order
Once the last packet has arrived, packets are reordered
If a packet is missing/corrupted, it is requested again

How does aysmetric encryption work

In asymmetric encryption two keys are used:

Public key: a key known to everyone
Private key: a key known only to the receiver

Both keys are needed to encrypt and decrypt information
Where
Person A uses a public key to encrypt their message
Person A sends their message over the network or internet
Person B decrypts the message using their secret private key

Symmetric encryption

Use a key + algorithm to encrypt data
uses the same key to encrypt and decrypt data
The aglorythm is used to convert plain text to ipher text

What are the characteristics of a robot

Mechanical structure
Electrical compinets
Are programable

Expert Systems

Have a knowlage base, a rule base, interference engine and an interface

Machine learning

When a program has the ability to automatically adapt toits own procceses and or data

How does antivirus work

Scans for viruses on computer
Using a record of known viruses
Removes any viruses found.

How do Led screens work

consist of two conductive layers. The top layer is flexible. When the screen is touched the two layer connect, completing a circuit

How do capacitative screens work

Made up of a protective layer, a transparent conductive layer and a glass substrate. Touching the screen changes the electrostatic field of the conductive layer

Benefits of resistive and uses

+ Cheap to produce.

+ Resistant to surface contaminants

+ Can be activated with nearly every object (stylus, finger, gloved hand)

Ised in kiosks

Advantages of infrared

+ Excellent image quality,

+ high precision

+ durable

+ allows for multiple touches at the same time

- Requires a bare finger or stylus for activation

Used in smartphones

Dlp projectors

DLP systems use millions of micro-mirrors arranged in a grid on a microprocessor within the projector.

Light is shone through colour filters and the mirrors. The position of the mirrors can be altered to change the intensity of the light

LCD projectors

LCD projectors use three mirror filters to separate an image into red, green and blue wavelengths. The three images are then combined to produce the full colour image which is passed through the lens on to the wall/screen

How do inkject printers work

Have a print head which moves across the page

Spray liquid ink droplets from ink cartridges through very fine nozzles onto the paper (these are in the print head)

The droplets can be piezoelectric or thermal bubble technology

Inkjet printers produce high quality hard copies of digital images or documents

Laser printers

Are very fast when making multiple copies of a document

Are useful for high volume print jobs for example producing leaflets

LCD screens

LCD screens are made up of millions of tiny liquid crystals.
The display is made of pixels arranged in a matrix

Led screen

Light emitting diodes (technology);

Similarity between phishing and pharming

Both are methods of social engineering, where you pose as a real person to steal people's information

Why is HDD a good storage device

It is cheaper per unit has longevity

How do USB drives flash data

Data is flashed onto silicone chips
Uses nand nor technology and transistor to controlo electrons

How do cookies work

Web server sends cookie to browser. Users infor is stored on an encrypted file
The cookie is stored in the hdd

Why is SSD usefal

Small and compact
High capacity
High speed

What is a url

Text based version of a web addres

What are methods of preventing spying

Drop down boxkes
On screen keyboard

Blockchain

A block chain acts as a ledger

How does RLE work?

a data compression technique that replaces repeated values with a count and the value itself

System software

Provides the services the computer requires e.g operating system and utility software

Application Software

Software that provides the services the user requres

Functions of os

Managing memory
Managingperipherals
Managing files
Managing profiles
Multitasking

Functions of a web browser

Stores bookmarks
Allows multiple tabs
Provides navigation tools.
Stores cookies