ALU
Arithmetic Logic Unit
-Performs calculations and logical operations
- Includes float point multiplication, integer division, comparison tests
CU
Control Unit
- The control unit manages machine code execution
- Signals sent via control bus to connected devices
- Sychronises instructions using the processor’s internal clock
Control Bus
- Used by the CPU to communicate with devices that are contained within the computer
- Connects internal components to the motherboard.
Registers
PC - Stores address of next instruction. Increments with each new instruction
MAR - Contains address of instruction to be fetched
MDR - Contains fetched instruction
CIR - Contains instruction being decoded/executed
Accumulator - Stores ALU results
General Purpose Registers
- Used while programs are running. Can be used for any purpose programmer chooses
Pipelining
- An instruction being fetched while an instruction being executed
Cache
- Minimises wasted clock cycles when a program is loading necessary instructions and data
- Faster access than RAM
- Stores frequently accessed data
Cache Miss
- A piece of data is not found in the cache
- Slows to execution time
Cache Levels
1: Fast, Small, Embedded in CPU
2: Bigger capacity, Slower, On a chip to avoid slowing down traffic
3: Improves on level 1 and 2, Shared by cores
Parallel Processing
- Splits the FDE cycle into threads, multitasked by cores, speeds up execution time.
- Some time lost to organising/communication.
Core
- A unit which can execute instructions.
Optical Character Recognition
- Turns printed documents into editable text.
- Digitises books.
- Allows written documents to be edited.
- Special characters might be missed.
- Has to be read after to ensure accuracy.
Optical Mark Recognition
- Scans for marks on a form.
- Efficient for marking multiple choice exams.
- Efficient for mass amounts of data.
- Might miss marks that have been amended/not drawn on in a certain way.
Magnetic Ink Character Recognition
- Checks for iron oxide ink.
- Detects fraudulent cheques.
- Quickly reads cheques.
- Someone within the bank could pass.
- Cheques are outdated.
Touch Screens
- Send co-ordinates to the operating system depending on where has been touched on the screen.
- Resistive screen cheaper, Capacitive (more efficient version) available.
- Easy to use.
- Capactivie doesn’t work with gloves.
- Can only register one touch at a time.
Magnetic Storage
- Read/Stored on arm with a special read/write head.
- As the disc spins, head travels across it, transfers data on disc in binary.
- Cheap, Good capacity.
- Faster ones more expensive, Develops errors overtime.
Flash Storage
- Retains state without power.
- Electronically Erasable Programmable Read Only Memory.
- Better performance than a hard drive, No moving parts.
- More expensive, Lower capacity.
Optical Storage
- Lasers burn indents into disc.
- ‘Pits and Lands’ binary.
- Capacity, Cost, Size for mass media is good.
- Rewritable discs are expensive/slow, Fragile, Sun damage.
Fragmentation
- When memory is rewritten, data gets split up in memory.
- Slows down execution time, Disc head has to physcically travel further to reassemble file segments.
- Defragmentation prevents this.
- SSD is direct access memory, Only bonus is ‘trimming’ speeding up execution slightly, Will shorten life.
Peer-To-Peer
- Every device on the network has the same access level.
- They are all connected to each other directly.
Client-Server
- Every device is connected to the server. Server has highest access level.
- Every request goes through server.
Network Interface Card
- Allows a device to connect to a network.
- Every network devices needs one.
- NICs have a port to allow the device to connect a cable.
- WNIC for portable computers. ‘Wireless enabled’.
Hub
- For smaller networks. Low traffic.
- Each packet is broadcasted to every connected device. Only the device with the desired destination of the packet takes it.
- Cheap to set up.
- Devices connect using a cable.
Switch
- Connects devices together on a network.
- Switches receive data packets from a connected node, read the destination address, and send the packet to its designated node directly.
- The switch determines the route using the route table.
- MAC address.
