Topic 5-Computer Hardware Flashcards
Central processing unit (CPU)
- The CPU (central processing unit) is often referred to as the ‘brain’ of the computer
- Its main role is to process programs and data
- It does this by repeatedly fetching an instruction from memory and executing it (fetch-execute cycle)
Component-Control unit
- Decides which instruction to carry out next
- Fetches it from memory
- Decodes the instruction and executes (or obeys) the instruction
- Repeats the process (fetch-execute cycle)
Component-Arithmetic and logic unit(ALU)
- Carries out arithmetic calculations,e.g addition,multiplication,subtraction,division
- Preforms logical comparisons to assist with decision-making by using the operators AND,OR and NOT
Component-Immediate access store (IAS)
- Stores all programs and data temporarily while they are in use
- During the fetch-execute cycle,instructions are fetched from their specific storage location in the IAS using an address
Fetch-execute cycle
- The CPU includes a number of registers
- These are high-speed memory locations,each used for specific purposes
- The registers below have an important role during the fetch-execute cycle
Registers-Program Counter (PC)
- A PC stores the address (memory location reference) of the next instruction to be fetched.
- It is automatically incremented by 1 every time wn instruction is fetched
Register-Memory Address register (MAR)
The address of the current instruction or data being executed is temporarily stored in the MAR
Register-Memory data register (MDR)
This register will temporarily store data being fetched from or written to the main memory of the CPU
Register-Instruction Register (IR)
This register temporarily stores the current instructions to be decoded and then executed
Accumulator
When calculations take place on data,the results are initially stored in the accumulator before being transferred and stored in the main memory
Factors that influence the speed of processing-Clock speed
- The clock speed measures the number of instruction cycles the CPU can deal with in a second
- The standard unit of measurement for clock but speed is gigahertz (Ghz)
Factors that influence the speed of processing-Cache
- Cache temporarily frequently used instructions and data
- It is quicker to search cache memory than RAM,thus increasing processor speed
Factors that influence the speed of processing-Processor Core
- A core can be defined as a single processor
- More advanced CPUs contain more than one core,which will increase their ability to run many programs at the same time,for example,a ‘quad core’ processor has four processors
The purpose of a microphone
- Accepts sound input or human voice into a computer system
- A voice recognition system can convert sound to text
Advantages of a microphone
- Faster to speak using a microphone than typing words using a keyboard
- It is hands free,allowing users to carry out other activities at the same time as voice input
Disadvantages of a microphone
- The recognition rate of spoken words can be low if there is background noise
- Sound files require greater storage capacity than text files
Purpose of a mouse
- Used to control the pointer/cursor on a VDU
- Uses built in sensors to detect movements and send corresponding signals back to the computer
- Also includes buttons used to make selections on the screen
Advantages of a mouse
- Easy to use and requires little or no training
- Quicker to select menus and icons compared to using a keyboard
Disadvantages of using a mouse
- Experienced users find it slow compared to using ‘hot keys’
- Need a flat service (additional space) to function properly
Purpose of a graphics designer
- Allows a user to hand-draw images,which are captured by the computer
- Consists of a flat electronic sensitive surface and a stylus pen
Advantages of using a graphics designer
- More natural to draw diagrams with a stylus than with a mouse
- Using a stylus produces more accurate and detailed drawings
Disadvantages of using a graphics designer
- Not suitable for selecting menus snd pointing at menu items
- More expensive than a mouse
Purpose of a touchscreen
- Looks similar to ordinary computer screens,with a touch-sensitive surface/membrane
- When the screen is touched the position is calculated as a (x,y) co-ordinate
Advantages of a touchscreen
- User does not require much ICT competence compared to using a keyboard
- Users can select and enter options much faster than using a keyboard
Disadvantages of a touchscreen
- Limited number of options available on screen
- Screens can become dirty quickly
Purpose of a speaker
- Allows sound to be outputted
- May be internal or external speaker
- In addition to the hardware,a sound card needs to be fitted inside the computer
Advantages of a speaker
- Useful for visually impaired users:text or figures can be spoken by the computer
- Natural way to communicate with users
Disadvantages of using a speaker
- External speakers require additional desk space connected to using headphones
- Speakers can distract other users in the same office who are doing other tasks
Purpose of a laser printer
- A laser beam is used to scan the image of the page to be printed onto a drum by building a pattern of static electricity
- This attracts toners (printer ink) to reproduce the page
