Unit 1 : Components of a computer and their uses Flashcards
1
Q
What is the processor
A
- The processor is the brain of the computer, it executes instructions which allows programs to run
2
Q
What is the Arithmetic and logic unit
A
The ALU carries out all arithmetic and logical operations
3
Q
What is the control unit
A
- The control unit is a processor which directs the operations of the CPU, its jobs are :
- Controlling and coordinating the activities of the CPU
- Managing the flow of data between the CPU and other devices
- Accepting the next instruction
- Decoding instructions
- Storing the resulting data back in memory
4
Q
What is a register
A
- Registers are small memory cells that operate at very high speed. They are used to temporarily store data and all arithmetic, logical and shift operations occur in these registers
5
Q
What are the different registers
A
- Program Counter (PC)
- Accumulator (ACC)
- Memory Address Register (MAR)
- Memory Data Register (MDR)
- Current Instruction Register (CIR)
6
Q
What does the program counter do (PC)
A
- Holds the address of the next instruction to be executed
7
Q
What does the Accumulator do (ACC)
A
- Stores the results from calculations
8
Q
What does the Memory Address Register do (MAR)
A
- Holds the address of a location that is to be read from or written to
9
Q
What does the Memory Data Register do (MDR)
A
- Temporarily stores data that has been read or data that needs to be written.
10
Q
What does the Current Instruction Register do (CIR)
A
- Holds the current instruction being executed, divided up into operand and opcode.
11
Q
What are buses
A
- Buses are a set of parallel wires which connect two or more components inside the CPU.
- There are three buses in the CPU: data bus, control bus, and address bus.
- These buses collectively are called the system bus
12
Q
What does the data bus do
A
- This is a bi-directional bus (meaning bits can be carried in both directions) used for transporting data and instructions between components
13
Q
What does the address bus do
A
- This is the bus used to transmit the memory addresses specifying where data is to be sent to or retrieved from. The width of the address bus is proportional to the number of addressable memory locations
14
Q
What is the control bus
A
- This is a bi-directional bus used to transmit control signals between internal and external components.
15
Q
What are the control buses signals
A
- Bus request: shows that a device is requesting the use of the data bus
- Bus grant: shows that the CPU has granted access to the data bus
- Memory write: data is written into the addressed location using this bus
- Memory read: data is read from a specific location to be placed onto the data bus,
- Interrupt request: shows that a device is requesting access to the CPU
- Clock: used to synchronies operations
16
Q
How does assembly language work
A
- Assembly code uses mnemonics to represent instructions, for example ADD represents addition. This is a simplified way of representing machine code.
- The instruction is divided into operand and opcode in the Current Instruction Register.
17
Q
What does the opcode do
A
- The opcode specifies the type of instruction to be executed.
18
Q
What does the operand do
A
- The operand contains the data or the address of the data upon which the operation is to be performed
19
Q
What is pipelining
A
- The process of completing the fetch, decode, and execute cycles of three separate instructions simultaneously
- Data is held in a buffer in close proximity to the CPU until it’s required
- Pipelining is aimed to reduce the amount of the CPU which is kept idle.
20
Q
What is the Von Neumann architecture
A
- Von Neumann includes a single control unit, ALU, registers and memory units
- Shared memory and data bus used for both data and instructions.
21
Q
What is the Harvard architecture
A
- Physically separate memories for instructions and data
- More commonly used with embedded processors
22
Q
Advantages of Von Neumann Architecture
A
- Cheaper to develop since the control unit is easier to design.
- Programs can be optimized in size
23
Q
Advantages of Harvard Architecture
A
- Quicker since data and instructions can be fetched in parallel.
- Both memories can be different sizes
24
Q
What is contemporary processing
A
- Contemporary processors use a combination of Harvard and Von Neumann architecture. Von Neumann is used when working with data and instructions in main memory, but uses Harvard architecture to divide the cache into instruction cache and data cache
25
What is Reduced Instructions Set computers (RISC)
● Small instruction set
● Each instruction is one line of machine code
● Used in common computers
● Pipelining is possible since each instruction takes one clock cycle
26
What is a Complex Instruction Set Computers (CISC)
● Large instruction set
● Instructions are built into the hardware
● Used in microcontrollers and embedded systems
● The compiler has less work to do
● Less RAM is required to store the code
● Many specialised instructions are made, even though only a few of them are used
27
What is the graphics processing unit (GPU)
● A co-processor made up of lots of independent processors
● Efficient at tasks such as image processing and machine learning
28
What is a Multi core systems
- Multi core CPUs have multiple independent cores that complete separate fetch-execute cycles
29
What is a parallel system
- Parallel systems complete multiple instructions simultaneously using techniques like pipelining, it can be completed using a single core and threading
30
What are some examples of input devices
○ Keyboards
○ Webcams
○ Magnetic stripe readers
○ Barcode readers
- A touch screen is both an input and an output device
31
What are some examples of output devices
○ Speakers
○ Printers
○ Projectors
- A touch screen is both an input and an output device
32
what are some performance factors for both input and output devices
- Speed
- Accuracy
- Cost
- Relevance to task
33
What is optical storage
Read from and written to using lasers
○ Binary information represented by portions of the disc which either reflect or scatter the incident laser light:
■ A pit scatters light and represents a 0
■ A land reflects light and represents a 1
○ Pits and lands are written in spiral tracks on the disc’s surface
34
What are some types of of optical storage
- CD
- DVD
- Blu-Ray
35
What is a CD (optical)
■ Stands for compact disc
■ Use optical technology to store small quantities of information
■ Most commonly used for audio files
■ Can also be used to store text and digital images
■ Small, thin and light so very portable
■ Easily damaged by scratches
■ Limited storage capacity
■ Relatively slow transfer speeds
36
What is a DVD (optical)
■ Stands for digital versatile disc or digital video disc
■ Higher storage capacity than CDs
■ Suited to storing digital videos
37
What is Blu-Ray (optical)
■ More than five times as much storage than traditional DVDs
■ Useful for storing high-resolution films
38
What is Magnetic storage
○ Represent binary information using two magnetic states :
■ Polarised
■ Unpolarised
○ Most common type is hard disk drives
○ Magnetic tape also stores information magnetically
39
What are some types of Magnetic storage
- Hard disk drive
- Magnetic tape
- Floppy disks
40
What is a Hard disk drive (magnetic)
■ Typically have high capacities of between 500GB and 5TB
■ Rotate magnetic platters at high speeds under a read/write head on an actuating arm
■ Most will have multiple platters stacked to maximise storage capacity
■ Have somewhat slow data transfer speeds
■ Many moving parts introduces tendency to be damaged by movement
41
What is magnetic tape (magnetic)
■ First used to record computer data in the 1950s
■ Popular storage medium through to the 1980s
■ Long stretches of tape wound onto reels passed through readers
■ A space consuming way to store data
42
What is a floppy disk (magnetic)
■ A thin magnetic disk enclosed in plastic to protect the disk from dust and dirt
■ Thin size and low weight made them extremely portable
■ Typical storage capacity of 1MB
43
What is Flash Storage
○ Fast and compact
○ Silicon semiconductors form the logic gates NAND and NOR
○ Logic gates used to store electrical charge in one of two states: high or low
○ Information stored in blocks, combined to form pages
○ Preferred logic gate used for storing small quantities of data is NOR
○ NAND is the preferred technology for larger files
○ Can be erased and reprogrammed electronically
○ Is non-volatile
○ Flash memory is generally more expensive per gigabyte than other methods of data storage
44
What are some examples of flash storage
- Solid State Drives
45
What is a solid state drive (flash)
■ Extremely light and portable
■ Have no moving parts
■ Much more resistant to damage from movement than hard disk drives
■ Renowned for high data transfer rates
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■ Primary disadvantage is cost
■ Another disadvantage is limited lifespan
● When a page is written to, the voltage required increases
● Over time, this will become too high
46
What is RAM
○ Random access memory
○ A type of fast, volatile main memory
○ Used to store data and programs that the computer is currently using
○ Speeds up the computer’s execution
○ Higher access speeds than even flash memory
○ More expensive per gigabyte than secondary storage devices
○ Computers often have only 4 or 8 GB or RAM
47
What is ROM
○ Read only memory
○ Non-volatile
○ Cannot be modified
○ Once programmed, the state of the memory cells inside does not changed
○ Useful for storing fixed sequences of instructions like a computer’s startup
(bootstrap) routine
48
What is virtual storage
● Name given to storing information remotely so that it can be accessed by any computer with access to the same system, for example over the Internet
● Examples include cloud storage services and networked storage used in offices and schools
● As internet speeds increase, virtual storage is becoming more popular
● Often an abstraction of multiple drives acting like one
● Disadvantages include limitations of a user’s network speed and high costs
