Chap 3 - Hardware

CPU

central processing unit, processes all the instructions and data in a computer so that a result can be output

integrated circuit

is a complete system that combines multiple parts working together to preform tasks together.

arithmetic and logic unit

ALU, the component of the CPU that carries out all arithmetic and logical operations

acumulator

ACC, temporary general-purpose register that stores numerical values at any part of a given operation

memory address register

MAR, a register that stores the address of the memory location currently being read from or written to

program counter

Holds the memory address of the next instructions to be executed. Increments by 1 as the fetch-decode-execute cycle runs

current instruction register

CIR, a register that stores the current instruction being decoded and executed

memory data register

MDR, a register that stores data that has been read from memory or data that is about to be written to memory

control unit

the component of a computers CPU that ensures synchronisation of data flow and programs throughout the computer by sending out control signals along the control bus

system clock

produced timing signals on the control bus to ensure synchronisation takes place

clock cycle

clock speeds are measured in terms of GHz, this is the vibrational frequency of the system clock which sends out pulses along the control bus, for example a 3.5GHZ clock cycle means 3.5 billion clock cycles a second

immediate access store

IAS, memory that holds all data and programs needed to be accessed by the control unit

backing store

a secondary storage device (HDD OR SSD) used to store data permanently even when the computer is powered down

cache

is temporary memory using static RAM to hold frequently used data/instructions by the CPU thereby increasing CPU performance. More generally, cache means any area of storage used to quickly access frequently used data (web cache, database cache, DNS cache)

register

a temporary component in the CPU which can be general or specific in its use, it holds data or instructions as part of the Fetch-Decode-Execute cycle

address bus

unidirectional, carries addresses, data is written to/read from

data bus

bidirectional, the system bus that allows data to be carried from CPU to memory or to and from input/output devices

control bus

bidirectional, carries commands and control signals to tell components when they should be receiving reads or writes

over clocking

changing the clock speed of a system clock to a value higher than the factory/recommended setting

core

a unit on a CPU made up of an ALU control unit and registers a CPU may contain a number of cores

Fetch-Execute-Decode

a cycle in which instructions and data are fetched from memory, decoded and finally executed

Basic Input/Output System (BIOS)

a suite of programs on firmware that are used to perform the initialisation of a computer system during the boot-up process

opcode

part of a machine code instruction that identifies what action the CPU has to perform

operand

part of a machine code instruction that identifies what data is to be used

instruction set

a list of all the commands that can be processed by a CPU and the commands are machine code

embedded system

a combination of hardware and software designed to perform a dedicated function

Barcode scanner (input)

reads barcodes to capture product information, used in supermarkets, warehouses, libraries
quickly and accurately retrieves product details

Digital camera (input)

captures photographs/videos as digital images, used for photography, smartphones, webcams
high quality visual content

Keyboard (input)

inputs text and commands by pressing keys, used in computers, tablets, laptops
type documents, enter data and control software

Microphone (input)

captures analogue sound and converts it into digital signals, used in recording studios, smartphones and computers
audio recording and voice communication

Optical mouse (input)

moves the cursor on the screen based on hand movements over a surface, used in computers and laptops
precise control and navigation on a computer screen

QR code scanner (input)

reads QR codes to access stored information, used in retail shops and mobile apps
quickly retrieves data from QR codes

touch screen (resistive) (input)

detects touch by pressing a flexible screen layer, used in ATMs, older smartphones
direct interaction with device

touch screen (infra-red) (input)

detects touch by interrupting infrared light beams across the screen, used in kiosks and large touch displays
accurate touch detection and works will in various lighting conditions

touch screen (capacitive) (input)

detects touch through changes in electrical charge on the screen surface, used in modern smartphones and touch monitors
smooth, responsive touch experience with multi-touch capabilities

two-dimensional (2D) scanner (input)

captures flat, 2D images of documents or photos for offices, libraries,
digitise documents and photos for storage, editing

three dimensional (3D) scanner (input)

captures detailed 3D shapes and dimensions of objects used for manufacturing, design and medical imaging
creates digital models of objects for design

actuator (output)

converts energy into motion, makes things move and performs physical taks based on instructions from a computer or control system. Used to make a robots arm move and rotate a motor
essential in any system that requires movement

digital light processing (DLP) projector (output)

projects images onto a screen, shows images or video by shining light through tiny mirrors, used in classrooms, cinemas.
high quality images

inkjet printer (output)

prints text and images onto paper by spraying tiny droplets of ink, used in schools and offices
low cost compared to other types of printers

laser printer (output)

heat from a laser fuses toner (fine powder) onto paper, used in schools and offices
high quality and fast printing

light emitting diode (LED) screen (output)

displays images and video using tiny lights called LED’s , used in televisions, computer monitors and smartphones
high quality images and energy efficient

liquid crystal diode (LCD) projector (output)

projects images or videos onto a screen by shining light through liquid crystal panels, used in home cinemas and classrooms
bright, good quality and affordable

liquid crystal display (LCD) screen (output)

displays images and videos using liquid crystal with a backlight, used in monitors and laptops. energy efficent, thin, lightweight

speaker (output)

converts electrical signals into analogue sound waves to play music, used in televisions and radios
multiple sizes and shapes

3D printer (output)

adds thin layers of plastic, one on top of another to form a three dimensional object, used in manufacturing, medicine and education

DAC

digital to analogue converter, device that converts digital data into electric currents (for motors, actuators)

ADC

analogue to digital converter, a device that converts analogue data into a form understood by a computer

random access memory (RAM)

• is primary storage that is directly connected to the CPU and holds the data and instructions that are currently in use

• RAM is volatile 

• For the CPU to access the data and instructions they must be copied from secondary storage

• RAM is very fast

• RAM is read/write

• Much larger capacity than ROM

• Stores part of the OS and programs that are currently running

read only memory (ROM)

• ROM is primary storage that holds the first instructions a computer needs to start up (Bootstrap)

• ROM contains the BIOS (Basic Input Output System)

• ROM is fast memory, but slower than RAM

• ROM is non-volatile

• ROM is read only

• smaller capacity than RAM

magnetic storage (description + pros and cons)

secondary storage that used platters which are divided into tracks and sectors which contain 0s and 1s. A read/write arm, moves the head over the surface of the disc to the location of the data which is read/written using electromagnets
examples - HDD, floppy disk
pros - high storage, cheap
cons - not reliable or portable, loud

optical storage

uses lasers to burn the surface of a disk, creating pits and lands suitable for storing binary 0s and 1s shining a laser across the surface of the disk and processing the reflection. The laser is also used to read the data from the pits and lands
examples - CD, Blu-ray, DVD
pros - portable, durable, not loud, cheap

cons - low capacity, slow

virtual memory

extension of primary storage (RAM). If RAM is almost full, virtual memory can be used to keep the computer operational. Programs and data not currently being executed are transferred to virtual memory. Programs are stored as pages of data. Pages of data are transferred between RAM and virtual memory when needed

pros - good backup, extends temporarily

cons - slow, negatively impacts performance

solid state (flash memory)

uses electronic circuits to store binary 0s and 1s. It uses NAND and NOR gates in electrical circuits to persistently control the flow of electrons. Transistors are used as control gates and floating gates.
examples - SSD, USB flash memory
pros - silent, fast, portable, durable, high capacity
cons - unreliable and expensive

cloud storage

long-term (secondary) storage of data that resides in a remote location, accessible only via a wide area network (Internet). Data is stored on remote servers

pros - reliability, security, capacity, collaboration
cons - expensive, availability

network interface card (NIC)

The Network Interface Card (NIC) is required for a computer to connect to a network. A NIC can be both wired and wireless and allows your computer to send and receive data over a network

router

sends data to a specific destination on a network
can assign IP addresses
can connect a local network to the internet

static and dynamic IP address

static IP addresses dont change, dynamic do

IP address

address is a unique identifier given to devices which communicate over the Internet. IP addresses make it possible to deliver data to the right device. A device connecting to a network will be given an IP address, if it moves to a different network then the IP address will change

IPv4 and IPv6

IPv4
- 32-bit address length
- lacks enhanced security
IPv6
- 128-bit address length
- generates more addresses

MAC address

a unique identifier which acts as a network address for a device. A network interface card is given a MAC address at the point of manufacture

Dynamic host configuration protocol

DHCP, is a server that automatically provides and assigns an IP address

microprocessor

a type of integrated circuit on a single chip

program counter

holds the address of the next instruction to be executed