systems software

what is an embedded system

computers that are built into other devices

usually dedicated systems

3 advantages of embedded systems

as they are dedicated to a single task, hey are easier to design, cheaper to produce and more efficient at doing their task than a general computer

what are peripherals

computer hardware that exists externally

what is the cpu and what does it do

the cpu is the brain of the computer

it processes all the data and instructions to make the computer work

what does the control unit do

manages the fetch decode execute cycle

controls the flow of data inside and outside the cpu

what does the alu do

control all calculations

contains the accumulator register

what is does the cache do

stores regularly used data so the cpu can access it quickly

what is cache (3)

very fast memory in the cpu

slower than registers but faster than ram

low capacity but expensive

what are cache levels

L1 L2 L3

L1 is the fastest but has the lowest capacity

L3 is the slowest but has the highest capacity

what are registers and what are 4 examples

extremely small and fast memory in the cpu

programme counter, accumulator, memory address register, memory data register

what does the cpu processing power depend on

cache size, clock speed, number of cores

what is von neumann architecture

a system where the cpu runs programs stored in memory

what does the accumulator do

stores results of calculations from the alu

what does the program counter do

holds the memory address of the instruction for each cycle

what does the memory address manager do

holds any memory address about to be used by the cpu

the address might point to data or an instruction

what does the memory data register do

holds the actual data or instruction that has been fetched from memory or is waiting to be written to memory

describe the fetch part of the fetch-decode-execute cycle (4)

memory address is copied from the PC to the MAR

the instruction stored in the MAR is copied to the MDR

the PC is incremented to point to the address of the next instruction for the next cycle

describe the fetch part of the fetch-decode-execute cycle

describe the decode part of the fetch-decode-execute cycle (2)

the instruction in the MDR is decoded by the CU

the CU prepares for the next step by loading values into the MAR or MDR

describe the execute part of the fetch-decode-execute cycle

the instruction is performed

e.g. loading data from memory, write data to memory, do a calculation or logic operation, change the address in the PC or halt the program

what does volatile mean

power is required to retain its data

what is clock speed and what is a typical value

the number of instructions carried out per second by a single processor - usually around 3.5GHz

what is overclocking

when a CPU is made to run at a faster clock speed than the factory-set rate

what are disadvantages of overclocking

if not done properly, CPUs may overheat, causing crashes or permanent damage so high performing cooling systems are needed

why is increasing the number of cores useful and how many are there typically

each core can process data independently so the more cores, the more instructions it can carry out at once - usually 4 or more cores

what is cache and why is it useful

data storage in the CPU that’s faster than RAM

a larger cache gives the CPU faster access to more data it needs to process

what are graphics processing units

specialised circuits for handling graphics and image processing that relieve the processing load on the CPU

what are 6 functions of an operating system

communicate with internal and external hardware via device drivers

provide a user interface so the user and computer can interact

provide a platform for various applications to run

allow multi-tasking by controlling memory resources and the CPU

deal with file and disk management

manage system security and user accounts

what are device drivers

translators that send signals to allow communication between the OS and hardware

advantage of graphical user interfaces

easy for everyday use as they are visual, interactive and intuitive

4 features of graphical user interfaces

WIMP - windows, icons, menus, pointers

what is a command-line interface

a text based interface used by entering specific commands

2 advantages of a command-line interface

less resource heavy than GUIs

for advanced users, more efficient and powerful and can be used to automate processes using scripts

how is multi-tasking carried out efficiently using memory managing and CPU processing times (5)

when an application is opened, necessary parts are moved to memory and removed when deemed unnecessary

a memory manager allocates certain applications to certain memory addresses to avoid applications overwriting and interfering with each other

CPU time is divided up between open applications according to the priority

data is moved to and from virtual memory

memory buffers are used to manage the flow of data so data is transmitted and processed at different speeds and times

what 3 ways does the OS use to manage files and disks

names, saves, deletes. moves and edits data

splits physical disks into storage sectors, decides which sectors to write to and keeps track of free space

uses utility software

what does compression software do

reduces the size of files by removing data from them as they’ll take up less disk space and be quicker to download

what does encryption software do

scrambles data to stop third-parties from accessing it so intercepted data remains secure

how is data decrypted

a key which only the intended users have and set of instructions are used to unscramble the data

why is defragmentation bad

reading and writing times become slower as the read-write head has to move back and forth across the disk

what does defragmentation do

reorganises data on the hard drive to put fragmented files together and collects all the free space together to prevent further fragmentation

why do SSDs not get fragmented

they use flash storage with no moving parts so data can be quickly accessed no matter how it’s arranged