Computer Components Flashcards
Purpose of computer
take data, process it, output it
Created to help process data and complete tasks more efficiently than humans
embed system
computers built onto other devices, system that is part of a larger system
dedicated to a single task, easier to design , cheaper to produce, more efficient at doing their task than a general purpose computer
what is control unit
overall control of the CPU, mangage fetching decoding and executing of program instructions by following the f-e cycle
controls the flow of data inside the CPU and outside the CPU
what is the arithmetic logic unit
does all the calculations
perform simple addition subtraction and compares the size of numbers and can do multiplicationa dndivision using repeated additon…
perform logic operations and binary shifts
contains accumulator reigster
what is cache
very fast memory in the cpu
slower than register faster than ram
stores regularly used data so cpu can access it quickly next time it is used, cpu checks cache first before checking the ram
they have low capacity and are more expensive compared to ram and secondary storage
different levels of cache memory l1 is the quickest and has the lowest capacity. l3 slower more capacity…
Von Neumann architecture
a system where the CPU runs instructions stored in memory
programs consists of instructions and data which are stored in memory address
inside control unit
the program counter which holds the address of the instruction of each cycle
it increments
registers
memory address register MAR
holds memory address about to be used by the CPU. address might point to data or a CPU instruction
memory data register MDR
holds the actual data or instruction
arithmetic and logic unit
accumulator
stores intermediate result of calculation in the ALU
fetch decode execute cycle
fetch instruction
copy memory address from pc to mar
copy instruction stored in mar address to mdr
increment pc
decode instruction
instruction in MDR is decoded by CU, cu them prepair for the next step
execution Instruction
the instruction is performed.
this could be load data from the memory, write data to memory , calculation or logic operation (using the ALU) change address in PC, or halt the program
repeat
Virtual memory
Secondary storage used as RAM
when ram is filled with data it uses secondary storage
it moves data that has not recently being used into secondary storage
used when using memory intensive apps or too many apps opened at once
it slow as data need to be moved back to RAM to be read again by cpu
slow to respond when switching applications
ROM
tells computer how to boot up
contains BIOs
clock speed
number of instruction one processor carry out per second
higher Clock Speed more instruction can be carried out
some CPU can be overclocked it can make CPU overheat /crashes/ permanent damage to system.
cooling system is normally needed to accompany high performance
number of cores
each core process data independently to the rest.
more core means more instructions at once
cache size
data storage inside CPU faster than RAM
larger CPU gives the CPU faster access to more data it need to process
RAM size
volatile
more ram means faster/smoother system
little ram make computer slow due to Virtual Memory being used
more ram means more applications or more memory intensive apps can run smoothly
ram is easy to upgrade - just need to replace the ram stick with higher capacity ones
excess ram makes no performance difference
GPUs
help CPU process image
used to handling graphics and images it relief the processing load on the CPU
computers have GPU integrated into motherboards or CPUs, for better performance dedicated GPU are used
Primary storage
memory CPU can access quickly
CPU registers, cache, ROM, RAM
mostly volatile
Secondary storage
non volatile
HDD (hard disk drive)
- stacks of magnetised metal disks that spin thousands of times per seconds and is read and read by a moving arm
solid state drives
- Faster more Reliable, no moving parts,
- hybrid drives uses SSD for OS and programs
other types of flash storage
USB pen drive and memory card (sd card)
also flash based, solid state storage
slower than ssd
used to expand storage of small devices
high capacity relative to their size
Advantages to using SSD and HDDs
HDDs
- cheaper
- both are high capacity, HDDs are higher
- longer read write life than SSD
SSD
- faster
- don’t need defragmenting
- silent
- shock proof
Optical Disks
CDs, DVDs and blue ray
CDs 700mb
DVDs 4.7gb
BluRay 25gb
3 forms
read only
write once
rewritable
use is declining
very slow not reliable
very cheap wont be damaged by water or shocked (although easily scratched)
Magnetic tapes
much greater storage capacity than HDDs
extremely low cost per GB
used by large organisations in archive libraries to store huge amounts of data
comes in plastic cassettes (containing reels of tape)
read/write sequentially, does it from beginning to end k
slow at finding data but can be quickly read once its found
functions of an OS
- communicate with internal and external devices via device driver
- provide user interface
- provide platform for different applications to run
- manage security
- Multi-tasking by controlling memory resources
- file management, disk management
Device Drivers
- a ‘translator’ for signals between OS and hardware
- os choose correct device drivers for the hardware it detects, new hardware connected will require system to install a new matching driver
- device manufacturer may release new drivers to fix bugs, add feature, or improve performance
defragmentation
In HDDs
when files are moved, deleted, change size small gaps appear on disk,
OS split files into smaller blocks to fill up the gaps,
over time file becomes more and more fragmented this makes reading and writing files slower, as the read/write head need to move back and forth the disk
defragmentation software reorganises data put fragmented files together. It also moves files to collect all the free spaces to prevent further fragmentation
Compression
reduce size of file by permanently or temporarily removing data from them,
compressed files take up less disk space and are quicker to download
format includes .zip and .rar
they need to be extracted before use
encryption
protects data
cypher (scrabbles) data to prevent third party from accessing it.
main benefit is that intercepted or stolen data is still secure as only the intended readers can unscramble them
to decrypt a special key is required; computer uses the key to revert it back to its original form
