Components of a computer sytem

Components of a computer sytem

1. Computer systems

   • hardware is the physical components
     • Software is the programs or the applications that the computer runs
   • Embedded systems are computers built into other devices
     • E.g. dishwashers, microwaves, TVs
     • often used to control and monitor machinery
   • Components
     • power supply
     • case cooling fan
     • heat sink
     • CPU
     • graphics card
     • optical drive
     • RAM sticks
     • Hard disk drive
     • Motherboard
   • The CPU
     • made of the control unit (CU), arithmetic logic unit (ALU), cache
       • CU executes all the instructions and controls the flow of data
       • ALU does all the calculations and logic operations, it also contains the accumulator
       • Cache stores regularly used data so it can be quickly accessed
         • has low capacity; very expensive and has 3 tiers
   • Von Neumann design
     • Fetch-> copy memory address from MAR to program counter, Copy instruction stored in MAR to MDR, Increment the program counter
       • Decode-> Instruction in the MDR is decoded by the Cu
         • Execute-> Instruction is performed

2. Memory

   • Ram
     • Random access memory
     • Volatile -> temporary memory, requires power to retain
     • operating system is copied from secondary storage to Ram when computer is booted
     • Is slower than cache
   • Virtual memory
     • when RAM is full , computer sends data to virtual memory
     • has to move data back and forth between RAM and virtual memory which is very slow
     • can make computer slow to respond when switching between apps
   • ROM
     • Read only memory
     • built into motherboard
     • Contains instructions to boot up computer
     • Can't be edited
     • Non-volatile ->permanent memory

3. Performance

   • Clock speed
     • number of instructions a single processor core can carry out per second
     • normally around 3.5 GHz
     • overclocked is faster then factory rate
       • can be risky and cause overheating, crashes or damage
   • cores
     • Each processes data independently
     • Most computers have 4
   • cache
     • larger allows faster access to data
   • GPU
     • graphics processing unit
       • handles graphics and image processing
       • greatly improve gaming and design software

4. Secondary Storage

   • all non-volatile
   • HDDs (Hard disk drives)
     • data stored magnetically in sectors within circular tracks
     • moving arm reads data to access sectors
     • portable for backing up and transporting large amounts of data
     • long-lasting and reliable but can be damaged when droppped
   • SSD(Solid state drives
     • no moving parts, use flash memory
     • faster than HDDs
     • portable for transporting a lot of data
   • Optic discs
     • CDs, DVDs, Blu-ray
     • can hold around 700MB of data or 4.7GB or 25GB
     • use is declining
     • cheap, portable and not damaged by water or shocks, but can get scratched
   • Magnetic tape
     • bigger storage capacity than HDDs and very cheap
     • comes in plastic cassettes
     • very slow to read but fast write speed

5. Operating systems

   • interactive systems allow users to interact with the programs and change the result of them whlie they are running
     • multi-tasking systems can run many programs at the same time
       • multi-user systems allow many people to log into a computer at the same time.
         • Real-time systems run programs that need to react in a specific time like weather or stock-markets.