Unit 1

• program counter stores address of intruction to be fetched

• instruction is then read by MAR which then gets a copy of the address

• then using data bus, a copy of data is sent to MDR

• Control unit splits up the instruction into opcode and operand code and sends to CIR

• Value in PC is then incramented by 1

• More space for instructions and data in cache

• RAM needs to be accessed less frequently

• cache is faster than RAM, as inside processor

more programs are able to run at the same time

• More instructions can be carried out per second

• More cycles per second

• less time taken to run a program

A high level language which gives a series of instructions in a logical order

• organise use of main memory

• allows programs to allocate memory

• protects programs from each other

• Completes current FDE cycle

• Checks priority of interrupt

• if priority higher than current task

• Remove tasks with less priority and place in temporary stak

• load ISR

• when complete return item from stack and place into registers

• direct link created between two devices which is maintained throughout conversation

• DEVICES MUST TRANSFER AND RECIEVE DATA AT SAME RATE

• data arrives in a logical order meaning can be reconstructred faster

• there is no delay

however,

• bandwith is wasted when no data is sent

• ties up sections of network which cant be used until transmission done

Application Software

designed to be used by user to complete specific task

Utility Software

designed to perform a specific task related to the upkeep / improvement of computer

Open source

• free to use by anyone, user can view source code

• lower security

Closed source

• user needs license, can’t access source code

• higher levels of security

• POST - checks all hardware is working correctly

• Checks CPU clock, memory and processor

• Checks external memory devices connected

• translate and execute line by line, stops at error

• slower than compiler

• good for testing sections of code

• can be used on a range of platforms / devices if interpreter is available

• faster execution

• different bus for for instruction and data

• different physical memory for instructions and data

• single clock cycle to run an instruction

• can read and write whilst accessing instructions

stringname.length - returns length of string

string.substring(start,howmany) - produces letters in range

str() - converts to string

string.upper() / .lower - makes caps or lowercase

string.isupper() / .islower() - returns true or false

• high level code -> machine code : in one go. error sheet at end

• specific to OS / processor so may need to be compiled again for different device

• code can be run without a translator

• longest translator

• same bus for data and instructions

• same physical memory for data and instructions

• cheaper to design

• used in PC and small computers

• can’t read and write whilst accessing instructions

so as many jobs can be processed in the shortest amount of time ,

to make efficient use of recourses and have fast response times

• uses Von Neumann when working with data and instructions

• uses Harvard to divide data and instructions into separate cache

DNS used to resolve corresponding IP to its URL

sends a request to DNS resolver

resolver checks cache if doesnt hold URL passed to TLD which checks amd returns answer or passes to ANS

IP returned to client

or error if no resolution

A set of rules

Ensures devices can communicate with each other

So they interpret data and signals the same way

4 Different layers (ATIL)

Application - decides which protocol will be used

Transport - checks all network data recieved

Internet - sends data to other devices using IP

Link - hardware connection between the devices

a data structure holding multiple pieces of data.

accessible by a single identifier

it holds data of the same type

elements are accessed by an index

Consecutive pieces of data being the same, or else doesn’t offer great reduction in size

Desktop publishing

Word processing

spread sheets

web browsers

antivirus

disk defragment

compression

backup

repeated values removed and replaced with one occurrence along with how many times it should be repeated e.g.

AAAAAABBBCC

A6B32C

bubble sort

insertion sort

faster for smaller data set

• packets deconstructed

• packets sent, with header (containing info e.g. destination)

• packets take different routes (most efficient)

• if one route breaks can take another

• packets reconstructed

• can be transferred over very large networks

however,

• all packets must arrive before data recieved

• takes time to deconstruct and reconstruct

Multicore CPU:

• many independant cores carry instructions seperately

Parallel Sysyem

• Complete tasks w/ single core by using threading

uses 2 states which are represented using binary

• hard disk

• magnetic tape

• floppy disks

pros: high capacity, cost effective durable

cons: slow

uses silicone semi conductors

• e.g. SSD

pros: fast, portable

cons: cost

uses lasers to read and write

• CD

• DVD

• Blu-ray

pros: cheap, portable

cons: risk of loss, slow

stores address of next instruction to be processed

a character set which maps values to characters using 8 bits.

Reduced Instruction Set Computer

• small instruction set

• 1 instruction = 1 line

• takes many lines to complete an instruction such as multiply

temporary storage for data being processed during calculations

decodes instructions

sends control signals

• be 1NF

• no partial key dependencies (can’t depend on a secondary key)

Atomocity

Consistency

Isolation

Durability

A field which has a unique values for each record in that table

using algorithms to predict which instruction soon fetched. Then stored in cache.

Algorithms must be highly accurate + no guarantee it is right

No repeating groups of attributes

(Attributes shouldn’t contain more than a single value)

file.openread(“ “) - opens file to read

file.openwrite(“ “) - opens file to write

file.readline() - reads a line

file.writeline(“ “) - writes to line

file.close()

Frequently occurring data replaced with index and compressed data stored in dictionary

Good for repeating groups of data

E.g.

translates low level language to machine code (one-to-one basis)

operating system

device drivers

Complex Instruction Set Computer

• large instruction set

• used in micro controllers + embedded systems

• 1 line to multiply

• RISC creates more work for the compiler.

• RISC requires more RAM to store code

• RISC has pipelining available

• CISC has less work, requires less RAm and only has a few special instructions

a piece of memory used to store data

within the processor

PAGING

• memory split up into equal size pages

• uses virtual memory

• physical divisions

SEGMENTATION

• memory is divided based on program flow

• logical divisions

• uses virtual memory

VIRTUAL MEMORY

• section of hard drive acts as RAM when not enough space.

• Sections of programs currently not being used moved here to free space in RAM

• PROBLEM CAN HAVE DISK THRASHING (FREEZING) DUE TO SWITCHING BETWEEN HARD DISK AND MEMORY

harvard

• more expensive

• has different memory and bus for data and instructions

• fixed memory size

• buses can transmit and recieve simultaneously

• mainly used in super computers

von neumann

• chaper, faster to develop

• takes more cycles to complete a task

• same bus and memory for data and instructions

• used in PC’s

operand gives the address of a register which holds another address, where the data is located.

An index register is used, which stores a value. The address of the operand is determined by adding the operand to the index register.

operand is the actual value.

operand gives the address which holds the value . Direct addressing is used in LMC.

• Is 2NF

• No non key dependencies (only depends on primary key and nothing else)

one which contains a CPU and GPU

makes use of multiple queues, each ordered based on a different priority.

can be difficult to implement due to deciding which job to prioritise based on a combination of priorities.

Half way between machine and object code - independant of processor architecture so can be used on different OS and machines

Acts as a medium, collecting and sending data on behalf of user

links together two LANS

provides link between two dissimilar networks e.g. LAN and WAN

• safer from interception due to packets using multiple routes

• more efficient as routes are only tied up for short periods of time

Completes all arithmetic and logical operations.

different approaches to using a programming language to solve problems.

Split into imperative and declarative

use code which specifies the action to be performed

e.g. procedural and object orientated such as python

stating desired result rather than exact series of instruction required to perform it.

E.g. functional and logical languages such as java and SQL

BRP could be followed by 2 possible instructions - only determined at execution. So wrong instruction may be fetched or decoded

A numerical address made of 4 numbers between 0 and 255

Uniquely identifies a device on a network

Transaction processed in entirety or not at all

Transaction must maintain referential integrity

Simultaneous executions of transaction should lead to same result

When transaction executed, it remains same regardless of circumstances

• uses a program called a spider which traverses the web

• takes in each word from page and adds an entry under the word in the index

• along with the position of the word in the page