SCD - Unit 1.1.2 + 1.1.3

Multipurpose Machines - Early Machines, only able to calculate an output using one set of instructions

Stored Program Concept - Programs are loaded into RAM, instructions go through FDE cycle sequentially, sequence can only be changed by a conditional or unconditional jump instruction

Von Neuman is the most common architecture (used in computers) Instructions and data are sorted in a common main memory, only 1 bus (shared), Cheap and not complex, simple CU design, data from memory and devices are accessed in the same way

Harvard separates data and instructions, separate buses (no competition for bus), used in phones and simple systems, more complicated and expensive CU.

Modern CPU's uses a combination, VN in RAM and Harvard for cache, some digital signal processors have multiple parallel data buses (prevents bottlenecks)

CISC - Large instructions set, uses as few lines of assembly, combines instructions, quick to code, computer has to translate less, requires less RAM

RISC - Opposite to CISC, min number of very simple instructions, each takes 1 clock cycle (no bottleneck), used to complete instructions in multiple general-purpose registers, simpler hardware (fewer circuits), RISC uses RAM and software to allow better CPU performance at less cost.

Multi-Core + Parallel Systems - Can distribute workload across multiple cores, better performance as tasks are being performed in parallel. Home PC's have 2-4 cores, Supercomputers have 1000's. Software has to be written to take advantage of multiple cores

Co-processor systems have an extra processor, supplements functions of the CPU has limited functions, may be used for floating-point arithmetic, graphics + digital signal processing, etc.

GPU - Specialised circuit, very efficient at manipulating computer graphics and image processing, has thousands of small efficient cores, process large blocks of visual data simultaneously, may be on a graphics card

Function of a GPU - Acts with a CPU to accelerate scientific, engineering, etc. applications. Used in many devices e.g. mobile phones, tablets, cars, drones, robots, etc.

Input devices sends signal to the computer/CPU, devices include keyboard, mouse, microphone, accelerometer, etc. Specialist Keyboards can be programmed for specific functions, mice can have a tackboard, whiteboards can have touchscreen/drawing device.

Barcode Readers use UPC-A (numbers only, retail+warehouses) or Code 128 (letters+numbers, transport + shipment tracking)

Scanners: 2D - converts paper document into computer-readable format | 3D - scan buildings, structures, medicine, tomography can be used (object sliced into <1mm thick slices)

QR codes - 2D barcodes that can be read by smartphones to link to websites or information

Sensors - collects data in analogue form and convert to digital, used in monitoring and control applications (a thermometer is a dedicated system)

Cameras - Used for photos, videos, facial recognition, etc.

Analogue - no discrete value, smooth changes, converted using analogue-to-digital converter (ADC)

Monitoring - Device will not make any changes to the process, only reports

Control - Device can alter a process, next value can be changed, output from device can affect the next input

Dedication systems - Pressure, acoustic, infra-red sensors, Gas, pH, Temperature, Moisture/humidity, light 

Monitoring Systems - Intruder detection + alarm system in a building, activated/armed by PIN code or alarm fob

Input > Process > Memory > Process > Output

Printers: Inkjet - Most common, sold at/below production cost, ink are dramatically marked up, uses CMYK (Cyan, Magenta, Yellow, Black), smudges easily with moisture and water | Laser - Fast, reliable, excellent quality, use dry powdered ink (toner), common in businesses | Dot Matrix - uses a matrix of dots instead of seamless line, poor quality, expensive, work effectively in dirty and damp conditions.

3D Printers - Use plastic filament/powdered resin that produces solid objects of any design, can have hollow parts. Medical applications - prosthetics, orthotics, surgery. Manufacturing and art - car parts, prototyping. Future - home needs, marketing, architecture, education, archaeology. Issues - a file for a working 3D gun was available in 2013 for everyone

RFID - Input/Output devices, use a transponder or receiver. Passive tags - bank cards, use radio waves from the receiver to get powered, needs to be close to receiver. Active - Uses large + battery-powered beacon, broadcasts signal up to 300m away (Shipping, toll stations, etc.)

RFID Uses - Security points, Identification, shipping, banking, payment, could replace barcode systems.

Actuator - Motors activated by an input sensor to control a mechanism (starting a pump, moving a washing machine)

Loudspeakers + Headphones - Digital data is sent from the PC to a DAC (Digital-to-Analogue Converter), converted to analogue, signal is then boosted using an amplifier.

LCD Monitors - (Liquid crystal display) contains groups of RGB diodes to form each pixel, Requires a backlight using LED's or Cold Cathode Fluorescent Lamps (CCFL's), LED's are more advantages as they reach max brightness almost immediately, sharper image, more realistic and vivid colours, brighter, small, last almost indefinitely, low power consumption.

OLED - Much thinner and lighter than LCD/LED screens, use plastic instead of glass (can be curved and much brighter), Generate own light so no backlight needed, consume less power and make less heat, larget FOV than LCD's

Multimedia Light Projectors - Compact, high-resolution, full colour, projects anything, usually has speakers, takes video signal and converts into a viewable image which is then projected onto a screen

RAM - Holds running parts of OS, running programs, data in use, volatile, can read and write to it, very fast

ROM - BIOS held here, Non-volatile, Data can only be read, needed as it holds boot-up instructions, without it the computer wouldn't boot up

On boot up. start-up instructions load the OS from the hard drive into RAM, with applications and programs they are copied into RAM from secondary storage

Virtual Memory - Part of the hard drive is used as an extension of RAM when it is full, slower as it is physically farther away from the CPU and has slower read/write speeds

Primary Storage - Volatile and usually refers to RAM

Secondary Storage - refers to non-volatile storage (magnetic, optical, SSD, tape), devices can have different technologies that have their own advantages and disadvantages (Durability, speeds, capacity, portability, cost, reliability

MB/s = Megabytes (Bigger), Mb/s = Megabits (8x larger number than MB/s), 200Mb/s = 25MB/s

Hard disks - concentric tracks on magnetic disk, sectors, spinning platters read by drive heads, high RPM: 3600-7200, data is written as sector moves under the head

Cloud Storage - Big servers of high-capacity hard disks, fast speeds, relatively cheap per TB

SSD's - Electronically programable non-volatile flash memory (e.g. USB), no moving parts (can survive extreme pressure, temperature, vibrations), faster than hard disks, limited life, durable, portable, expensive.

USB Drives - cheap, high-capacity, portable, can be password protected/encrypted, good for transferring data between devices.

Disks - Different wavelengths burn smaller pits (more tightly wound track which is longer), metal layer under plastic substrate (protections), can be read-only, recordable, rewritable

Software Mailing - suited to optical disks, cheap to manufacture and distribute, robust during transport, lightweight

CD-ROM (Read-only) - pressed at manufacturing (Software distribution) | CD-R (Recordable) - Written to once (Copying files) | CD-RW -Written, read and erased many times (Short/medium term backup, file transferring) | DVD + Blu-Ray (Feature-length films)

Hard disk - 12TB+, 100-200MB/s

CD-ROM - 700mb, 150KB/s

DVD - 4.7-8.5GB, 10Mb/s

Blu-Ray - 25-50GB+, 36Mb/s

SSD - 4TB+, 200-550MB/s +

Flash Storage - Data is written to a pool of NAND (NOT AND gate) flash so it can retain data when there is no power, used by flash drives and SSD's which has allowed high-capacity at a low cost