Computer Science UNIT1
- Computing
- Computer systemsHardwareNetworksProgrammingSoftwareSystems development lifecycleThe InternetETHICAL, ECONOMICAL, LEGAL, PRIVATE ISSUES
- GCSE
- OCR
- Created by: ellielewisss
- Created on: 13-03-18 11:32
COMPUTER SYSTEMS
a computer is a machine that processes data.
the purpose of a computer is to take, process and then output data.
a computer system consists of hardware and software that work together
EMBEDDED SYSTEMS
embedded systems are computers built into other devices, like a dishwasher
they are usally dedicated systems
they are usally dedicated to a single task
they are usally used as control systems- they control and monitor machinery
CPU
CENTRAL PROCESSING UNIT
CPU
CPU is the brain of a computer system
it processes all of the data and instructions that make the system work
the processing power depends on different characteristics; clock speed, core number and cache size
the CPU architecture describes the main components of the CPU and how they interact with eachother.
MAIN PARTS OF CPU
THE CONTROL UNIT (CU)
THE ARITHMETIC LOGIC UNIT (ALU)
THE CACHE
MEMORY
VOLATILE- temporary memory, needs power to keep data
NON-VOLATILE- permanent memory, keeps when power is off
RAM (RANDOM ACESS MEMORY) is used as the main memory in a computer, it can be read and written
RAM is volatile
ROM (READ ONLY MEMORY) can only be read, cant write onto it
ROM is non-volatile
VIRTUAL MEMORY
is secondary storage used as extra RAM
virtual memory may be needed if there are too many aplications open at once
using virtual memory can make a computer slow to repond when switching between aplications
ROM
tells the CPU how to boot up
ROM is a small chip built into the motherboard
it contains all the instructions a computer needs to boot up properly
these instructions are called BIOS (BASIC INPUT OUTPUT SYSTEM)
CPU can only read ROM, it is possible to update ('flash') the BIOS on a ROM chip.
ROM often uses flash memory.
CLOCK SPEED
this is the number of instructions a single processor can carry out per second
higher the clock speed = the greater number of instructions that can be carried out per second
some CPUs have a overclocked to make them run at a higher slock speed, it can make systems overheat causing crashes and permanant danage to the system
NUMBER OF CORES
each core in a CPU can process data independantly of the rest
the more cores CPU has the more instructions it can carry out
most pcs and smartphones have 4 or more cores now
CACHE
the cache is data storage inside the CPU thats much faster than ROM
a larger CPU cache gives the CPU faster access to more data it needs to process
GPU
GPU (GRAPHICS PROCESSING UNITS) are used for specialised circuits for handling graphics and image processing
computers have basic GPUs integrated omto the motherboard and CPU
for better graphics a graphics card is often used
STORAGE
PRIMARY STORAGE- refers to the memory areas that the CPU can access very quickly, primary storage has the fastest read/write speeds and is mostly volatile
SECONDARY STORAGE- is non-volatile. its where data is scored when not in use. includes magnetic hard disk, solid state drives, CDs and SD cards. much slower to program
MAGNETIC HARD DISKS
HDD (HARD DRIVE DISKS) are traditionally internal storage in PCs and laptops
data is stored magnetically in really small areas called sectors within circular tracks
portable HDDs are popular for backing up and transporting large amounts of data
despite it having moving parts it is genuienly very long lasting and reliable but they can be damaged by large impacts such as being dropped
SOLID STATE DRIVES
SSDs (SOLID STATE DISKS) are storage devices with no moving parts
same purpose as HDD and internal storage
faster read and write time than HDD, can boot up programs and files quicker than HDDs
HYBIRD DRIVES exist which use solid state storage for the OS and programs and a hard disk for data
like HDDs SDDs are portable and can be used to transfer data.
OPTICAL DISKS
are cheap and robust secondary storage
optical disks are things like CDs, DVDs and BLU-RAY disks
they come in 3 forms- read only, write only and rewriteable
advantages- cheap, portable, not damaged by water or shocks
disadvantages- scratch easily, low capacity, slow read/write time
MAGNETIC TAPES
advantages- greater storage capacity, low cost
disadvantages- can be easily lost, breaks easily
often used by large orginisations, can store lots of data
it is read/write from begining to end
MAGNETIC TAPES
advantages- greater storage capacity, low cost
disadvantages- can be easily lost, breaks easily
often used by large orginisations, can store lots of data
it is read/write from begining to end
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