Computer Science UNIT1

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 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

CENTRAL PROCESSING UNIT

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.

THE CONTROL UNIT (CU)

THE ARITHMETIC LOGIC UNIT (ALU)

THE CACHE

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

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

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.

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

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

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 (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

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

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

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.

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

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

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