What are the fundaments of a computer system
1) data is input
2) data is converted into an internal representation
3) the data is processed
4) the results of processing are converted from the systems internal representation to a user friendly out put by an output device
5) the data may be stored
6) the data may be used
7) the data may be transmitted to an additional computer while still holding the form of the computers internal representation
Define a computer system
A computer system is hardware and software working together to create a coded solution. It must be able to receive inputs process these and then produce an output
General purpose system
A general purpose system is usually found on laptops tablets and apart phones. A general purpose system is designed to perform a range of tasks and does not have one specific purpose.
Dedicated system
A dedicated system is a system used to perform single functions or a minuscule range of functions.
Embedded systems
Emmbeded systems are computer systems that are part of a larger system
Expert systems
Expert systems are systems that have a clear focus on a single task
Control systems
Control systems are systems that control machines , they are normally used in the manufacturing industry
Management systems
Management Systems collect data from several other smaller systems
What is the importance of computer systems in the modern world ?
1) they allow us to contact and work with people regardless of location
2) they mean data can be accessed securely from a range of locations
3) they improve quality of life , those without limbs can have them replaced by bionics
4) they save time thus services such as that of the fire , police and ambulance can coordinate responses quickly and swiftly implement resources using computer systems
What is the reliability of a computer system
The reliability of a computer system is how dependable it is to do the job you entrust it with.
Computer systems need to be reliable as technology is not worth possessing if it does not function correctly or puts your previous work at risk
Factors which can affect the reliability of a computer system include
- human error
- virus
- hardware malfunction
Professional standards
It is important that manufacturers of computer systems implement professional standards to ensure there is an element of quality control . It is the responsibility of the manufacturer to make the computer system safe for the consumer . The system must work within range of a suitable efficiency and hence must function correctly which can be ensured by obliging by professional standards
Ethics
When developing a computer system ethics must be considered hence the privacy of a user becomes a pressing question , can governments access user data , can peers access user data or is the data maintained as confidential . There also must be user access levels to ensure no sensitive information can be accessed by unauthorised personal which would be an ethical injustice in the case of computer stores of medical records and such alike
Environment
Computer systems must oblige by government energy regulations which consequently means they must coincide with a set standard of efficiency
Laws
Legal issues must be considered this a system must not violate laws such as those of copy right
what does CPU stand for
Central Processing Unit
What is the purpose of the CPU
The CPU is a piece of HARDWARE within a computer system whose purpose is to process data
What is the function of the CPU
Fetch - The CPU searches and retrieves instructions from the computers memory
Decode - the CPU breaks down the problem to enemies the computer can gain an understanding of the task
Execute - the CPU runs a task meaning the instruction the is ‘fetched’ is carried out
What is the importance of the CPU
1) the CPU connects items in a computer system together such as the memory and output devices
2) it is the central processor hence it has the capacity to dictate the response of a system based on an input
3) it can carry out several tasks within a period of time as it processes them sometimes simultaneously
How does the Number of cores affect the performance of the CPU
A CPU can have multiple cores , these allow for multiple instructions to be executed simultaneously . If a program is optimised to use more cores it will mean the program will run faster
What is the measurement of processor speed ?
Giga hertz (GHz)
How does the clock speed affect the performance of the CPU
The CPU needs to complete a certain number of ‘cycles’ to execute each task . The clock speed is the amount of cycles that can be executed in one second , the faster Jesé cycles complete the more tasks can be carried out per second . Increased clock speed in the CPU means increased performance of the computer system . Clock speed is measured in the same way as processor speed - in giga hertz (GHz)
How does the size of the cache memory affect the performance of the CPU
Cache is the type of memory that stores frequently accessed instructions so that they can be quickly fetched and executed when requested by the user . If the CPU has more cache memory it will have a better performance as more data will have a quicker retrieval time.
How would you explain our number system
Our number system is that which we call base 10 it has 10 digits
We refer to this number system as deanery
Explain binary
Binary is a base two system as it only uses two digits
0 and 1
In a computer system everything is represented by binary digits as they symbolise a voltage 1 being on while 0 is off
Boolean logic / logic gates
NOT gate
In a not gate the input is reversed as the gate is an inverter
Input. Output
- 0
- 1
Boolean logic / logic gates
AND gate
The gate revives two inputs and produces a single output , both inputs must be true in order for the out put to be be true
a AND b must switched on in order for a positive output to prevail
Input A. Input B. Output
1. 1. 1 0. 0. 0 0. 1. 0 1. 0. 0
Boolean logic / logic gates
OR gate
The gate revives two inputs and produces a single output , at least one of the inputs must be true in order for the out put to be be true
a OR b OR both must switched on in order for a positive output to prevail
Input A. Input B. Output
1. 1. 1 0. 0. 0 0. 1. 1 1. 0. 1
RAM
RAM = random access memory
- it’s a form of memory which can be accessed quickly
- it is volatile memory , every thing is lost if the device looses power
- it’s purpose is to store all the data associated with programs that are currently open
- it is a form of temporary storage
- if a computer has more ram it will run more quickly
- large capacity
- can be accessed and changed by the computer
- more RAM means better performance
ROM
ROM - Read Only Memory
- a form of storage that contains pre recorded data
- data in the ROM cannot be edited only read
- ROM is non volatile all data is retained even when the device looses power
- small capacity
- programmed during the manufacturing of the device
- the ROM contains essential programs such as Ines which allow the computer to start up
Virtual memory
Virtual memory is used when all of the RAM has been used up . It is an extension of the RAM
Data that has been held in the RAM that has not been opened in a while may move into the virtual memory. Data in the virtual memory can be accessed far more slowly than data in the RAM . Having a larger RAM means less is stored in the virtual memory this is a benefit as fetching from the virtual memory takes a lot longer
Cache Memory
Data that is frequently used is stored in the cache memory this means future requests can be served more quickly however it is a very expensive type of memory
Flash memory / solid state memory
Flash memory is a type of non volition memory that uses solid state technology . Flash memory has no moving parts this means the form of memory is more durable . The benefit to this type of memory is it can be accessed quickly and also can transfers data between devices as it can be easily moved around (memory sticks)
Advances in memory technology
As memory technology advances data retrieval is becoming much faster . The storage capacity of devices are increasing while the actual size of the storage device is getting smaller this means a computer can store more without increasing its size . It also means because of the reduced size Meier can be transferred between devices as it can be physically moved . Increased memory capacity increases the performance of a computer
Input devices
An input device enters data for processing it may include
- keyboard
- mouse
- scanner
- microphone
- light sensor
Output devices
An output device is something that delivers an output after the processing of an input
Some out put devices may include :
- printer
- speaker
- Monitor (non interactive touch)
- heater
Devices for people with specific needs
Brail keyboard (input) - to help users that are blind or visually impaired to type
Voice recognition (input) those who are physically incapable of using physical inputs can control the computer via the use of their voice
Brail printer (output) users whom are blind or visually impaired are this capable of reading the output of the computer system
Computational narration (output ) those whom have visual impairments are able to understand the display of the computer and Coke to know the results of the execution of the task
Secondary storage
Secondary storage is a physical attrition to the computer system it is not internal but rather added to the system
Secondary storage is important as it is able to retain the data stored in the RAM when the device looses power . Secondary storage is non volotile
Optical storage
Optical storage devices store data in patterns of dots that are burnt in to the disk usually using a powerful laser
These dots can be read through bouncing a laser beam over the surface of the medium . If the beam hits a dot the light is refracted back differently this difference can be detected thus the data can be read. Types of optical storage include
- CDs
- DVDs
- Blue-ray disks
Solid state storage
Solid state storage is essentially a type of storage that has no moving parts , they are formed using large electrical circuits . Solid state memory is fast , reliable and portable . It can be found in devices such as
- USB memory sticks
- memory cards
- SD cards in cameras
- SIM card in phones
Magnetic storage
Magnetic storage holds data in the form of tiny magnetised dots , these can be read using magnetic field s which are created using tiny electro magnets . Magnetic storage normally had a large capacity . It can be found in devices such as
- hard drives
- Magnetic tapes
- Floppy disks
When choosing a type of storage the following considerations should be made
Capacity - how much data can be stored
Speed - how quickly can data be read as written
Portability - how easy is it to travel with / can it be removed
Durability - how easily damaged is it
Reliability - how likely is it to malfunction
What is hardware
Hardware is the physical parts that make up the computer system
What is software
Software is the range of programs used to control the computer system
What is an operating system
An operating system is the essential peice of software that links hardware and other software applications together, some common operating systems include
- Android
- iOS
- windows
What are the functions of an operating system ?
Memory management - the operating system transferred programs in and out of various forms of storage , it also keeps track of memory usage per program and allocates free space
Peripheral management - the operating system opens closes and communicates with peripheral devices (additions / connected devices) to ensure the attached software works with the hardware
User interface - the operating system provides the user interface which is the screen the user perceives , this allows them to interact with the computer system without having to read the code and make additions
Multi tasking - the operating system allows multiple applications to run at the same time
Security - the operating system provides security through ensuring requests are legitimate and that users accounts are protected by passwords
What is a utility program ?
A utility program is an addition to the operating system that is designed to do one particular job
Utility programs - security
Utility programs can be added to secure a computer system
Anti virus software - antivirus software is a program which detects and eliminates malicious software
Fire walls - firewalls are a piece of software which filter in going and outgoing traffic to ensure nothing suspicious or harmful occurs
Spyware protection - spyware protection blocks threats that aim to gather and send information about the host
Utility programs - disk organisation
Utility programs can also be implemented as additions to the operating system in order to support in disk organisation
Formatting software - formatting software partitions sections of a secondary storage before files are stored
Defragmentation software - defragmentation software is that which reorganises data that is related so they are stored together and Janice can be accessed more quickly
File transfers - file transfer utility allows files in the storage devices to be copied moved and deleted
Utility programs - system maintenance
Utility programs can aid in the maintenance of a computer system
System clean up - speeds up performance by deleting old files
Automatic updating - searches online to find downloads and instantly updates when they are released
System information diagnostics - the specifications of hardware are kept and can be checked to ensure hardware is functioning in the correct manor
Types of software
Custom written - custom written software is software which is designed to meet singularly the requirements of a person or organisation
Off the shelf software - generic software designed to meet the needs of lots of people for instance Microsoft word
Open source software - a type of software that is free to download too anyone and which can be modified
Proprietary software - a closed source software that cannot be be modified or reverses engineered because he source code is not made public . Often you need a special license to purchase this type of software
Computing units
Bit = one binary digit
Nibble = four bits
Byte = 8 bits
Kilo byte = 1000 bytes
Mega byte 1000^2 bytes
Giga byte 1000^3 bytes
Terra byte 1000^4 bytes
What is an over flow error
An over flow error is an error that occurs when a calculation is ran by a computer but the answer is too large to be stored correctly . All computers have a predicted range of values they can represent and store , over flow errors occur when the calculation produces a value outside of this range.
In binary …
- +. 0. =. 0
- +. 1. =. 1
- +. 1. =. 10
- +. 1. +. 1. = 11
Hexadecimal
Hexadecimal is a base 16 system
0 1 2 3 4 5 6 7 8 9 A B C F
if you wanted to convert the number 184 into hexadecimal first you would write it out in binary
1 0 1 1 1 0 0 0
You would then split this number into two nibbles and work out he value of each nibble
1 0 1 1 1 0 0 0
11. 8 The 11th hexadecimal value is B and the 7th hexadecimal value of 8 hence 184 in hexadecimal would be written in hex as
B8
We use hexadecimal as fewer digits need to be used to store large numbers
What is a character
A character is a unit of information
What is a character set ?
A character set is a defined set of characters recognised by a computer systems hardware and software . Each character is represented by I binary number
ASCII
ASCII = American standard code information interchange
ASCII is based on the English language and represents 256 specific characters , each character has an 8 bit binary number hence there are a limited amount of characters this ASCII can only be used on basic English devices as it can only store a limited quantity of characters
Unicode
Unicode represents a far greater range of characters as each of its characters are represented by a 16 bit binary number his means it has a more complete range of characters and this can be used all around the world
Images
An image is a series of pixels represented by binary , most images are analog data so a computer has to digitalise them before it can read them , this is done through assigning each colour a binary value
What can affect an image
Colour depth / bit depth - the bit depth is the number of bits that can be used to represent a colour if there is a higher bit depth there is a greater range of colour hence more shades are possible and increased but depth will increase file size
Resolution - resolution is the amount of detail an image holds it is measured in dpi ( dots per inch) if there are more dots per inch there will be a better image however more dots per inch thus a higher resolution again means here will be a greater file size
Meta data
Meta data is data that is stored about data .an image is data the data that composed the image also has data stored about it for instance height, bit depth , width , date
Sound
Sound waves are a type of mechanical wave , they cannot be directly interpreted by a computer as they continually vary and computers need digital data sound waves are changed to digital waves through he process of sampling
What can affect sound
A faster sampling rate means that sound will have a better quality as the true value of the wave is measured more times
A greater sampling depth which means how many bits represent each sound will also improve the quality of the sound as a greater range of sound will be recognised and it will jot be limited to set values
A sound can be mono or stereo , mono sound means that if you were listening through a song through head phones and you had only one in the song would sound the same is if you had two in . Stereo sound means multiple sounds are heard hence when you are listening through head phones different sounds will come out of each
File size
File size = sample rate x length x number of channels (mono or stereo ) one or two
What is a data base ?
A data base is a persistent organised data store
Databases
You can et digital data bases or non digital data bases , they are used to record add and extract data . They are also used to collectivise and store data
DBMS
DBMS = data management system
A data management system is a system that bridges the gap between a data base and other appliances .
The DBMS allows the user to add edit and extract data and provides as set of tools for accessing and maintaining the database
A DBMS is independent from the data base itself
A DBMS will automatically check for issues this may keen validating data stored
The DBMS also implements security measures through controlling access to the data
The jobs of a DBMS
Security - the DBMS manages the system to ensure it is not manipulated and its data is not jeopardised by unauthorised personnel
Creation - the DBMS uses software to define and build structures to hold data
Maintenance - the DBMS uses software to maintain the data base and keep every thing up to date adding and deleting data were appropriate
Integrity - the DBMS keeps data in a consistent way so that it is correct and reliable upon access
Querying - the DBMS utilises software to search the data base for information of interest to the reader
Logged changes - the DBMS records who accessed the data base , when they accessed it and what they changed this helps keep track of the data
Data validation - the DBMS ensure the data that is input is reasonable
Components of a relational database
Entities - things that data has been collected about
Tables - two dimensional stores of data organised in rows and columns
Forms - the interface data is submitted into the data base on
Queries - requests for data
Reports - presentations of data from a data base
Moduals - things that are not built into the data base but are added for functionality
Components of a data base
A field - a single piece of information e.g. Age
A record - a collection of fields for instance name age sex d.o.b
Key field/primary field - a unique identifier for instance ID
Column - go down vertical
Row - go across horizontal
What is the purpose of a key field
A key field is used to connect data and avoids data redundancy
What is data redundancy
Data redundancy is where information is repeated
Data base verification
A verification check is used to check if the data input matches the original data source . It does not check that the data is correct just that it matches the original . To verify some data it could be :
- typed in twice and only accepted if the two inputs are identical
- compared side by side
GIGO
GIGO means garbage in garbage out . If the data you input is incorrect (garbage in) then the information you extract from the database will also be wrong (garbage out). Validation and verification are important to avoid this and ensure inputs are accurate and reasonable.
Types of validation
Data type - validating through Data type could mean in a column concerning age only inputs that are integers or real numbers can be accepted
Range check - a range check , checks data is within a centaur range for instance age normally wouldn’t be under 0 or over 200
Null check - this makes sure important fields in the data base are not left blank , for instance you always need an emergency contact number per child in a school data base
Length check - a length check makes sure the data input is above or below a certain limit for instance a phone number must have a certain number of characters as would a PIN number
Computer networks
Computer networks are connections between devices which allow data to be exchanged
LAN
LAN = local area network
A lan is a network that connects devices together that are in close proximity to one another for instance in a school or a house
WAN
WAN = Wide Area Network
A wide area network is a networked which spans a great geographical distance , more devices may hence be connected within a WAN it may connect things like chains of restaurants
PAN
PAN - Personal Area Network
A PAN is used to connect devices in a very small area for instance in a university dormitory it may only have very few devices connected within it
Advantages of using a LAN
The advantages of connecting a stand alone device to a LAN is
- files and data can be more easily be shared between devices
- devices can share hardware for instance printers so additional hardware does not need to be purchased
- data is stored in a central server and consistently can be backed and stored in a central server
- data stored in the central server can be retrieved from any device in the Network
What hardware is needed to connect a stand alone computer to a LAN ?
Switch - a switch has lots of ports to connect devices in the LAN it recognises devices in a computer system based on their MAC address and filters and forwards data to only the devices that request it
Hub - a hub has lots of ports to connect devices in a network , a hub forwards data to all devices in a network not only the Ines that request it like a switch would
Router - a router forwards data packets to ensure they reach their intended destination . A router connects different devices together such as the internet and a business network
Wireless access point - the wireless access point Is a piece of hardware which allows devices to connect to a wired network using wifi ( wirelessly)
Relationships within a network
Clients = computers which request information
Servers = computers which provide information
Client server - in a client server relationship the client is dependent upon the server to provide and manage information , the server dominates the relationship
- the server controls the security of the network
- the server manages the network
- clients are dependent on the server
- the server can be updated and made more powerful to cope with high demands
- data is backed up on the main server
Peer to peer - in a peer to peer network no single provider is responsible for being the server . Each device stored files and acts as a server . Each computer has an equal responsibility for providing data
- no central control over security
- no central control over the network
- clients are independent
- of computers in the network are slow they will slow all the other devices down
- each computer has to be individually backed up
Bus tropology
In a bus stop network all clients are connected to the same cable . The device has to send a signal down the cable to reach a server
Advantages
- it uses minimal cabling so it’s cheap
- it is quick to set up
- it is easy to instal
Disadvantages
- if one device fails the entire system fails
- if more than one work station is added performance is decreased as there can be data collisions
Star tropology
Most LAN networks are star topologies in a star tropology all devices share a single connection point and they are all independently Linked to it
Advantages
- they are reliable if one device fails the others continue to work
- their is a high performance due to low data collisions
Disadvantages
- they are expensive due to lots of necessary cabling
- if the central server fails the whole system goes down
Ring tropology
In a ring tropology each device is connected to two other devices which forms a ring messages travel around a ring until they meet an intended server
Advantages
- data is transferred in one direction so there are fewer collisions
Disadvantages
- if one device fails the whole system goes down
- there are privacy issues work stations may see data that was not intended for them
Key networking terms
Protocol - words that define the data transmission and ensure all data is sent in the same way so there are fewer errors
Packet - A packet is a unit of data which is routes between origin and destination
IP address - an IP address is a unique identifier for every device in a network using the internet, an IP address can be changed
MAC address - A unique identifier given to a device when it is manufactured . MAC = media access control . The MAC address of a device cannot be changed
Network policies
Acceptable use policy - terms that users must oblige by when using the network these are the terms are enforced by the operator . They aim to ensure their is no data misuse and data is not damaged .
Disaster recovery - this means networks have a back up of data incase there is an online attack or physical disturbance such as a fire
Fail over - a failover means that if a key price of hardware fails for instance a server another one will begin to function so that the system doesn’t go down
Archiving - data is kept stored even when it is not currently in use
Network security
User access levels - theses are the permissions in a network the user has . So a teacher may be able to do more on a network than a student
Password protection , passwords must be entered in order to be allowed onto the network witching the network further passwords may be required to access different user levels
Encryption - this means sending and storing data in codes so that it cannot be accessed in the case it falls into the wrong code only users with knowledge of the encryption key will be able to understand the data this means even if security is breached the hackers cannot gather data
What is the Internet
The internet is a world wide collection of networks
What is needed to connect a device to the internet
Modems - a modem converts digital data from the computer system to analogue data for transporting down phone lines and vide Versa
Router - a router forwards packets to Doreen’s devices through different networks . It ensures the data finds its way to its destination and ensures packets are only sent to devices which requested it
IP addresses
Every device connected to the internet had an IP address (internet protocol address) this IP address is used to send and receive data . Some devices have static IP addresses therefore theirs never change other devices have dynamic IP addresses hence they are assigned a new IP address every time the computer accesses the internet . Static IP addresses are sometimes considered more dangerous since they are easier to track for data mining purposes
The DNS
The DNS is the domain name system it is what connects the IP address and web pages . The name of a webpage is its domain name . The DNS translates non user friendly domain naked which may be a selection of numbers and translates it into a domaine name like http:// google.co.uk
The DNS contains a database of IP addresses and domain names and operates on a client to server network
What is HTML
HTML is hyper text mark up language . Sir is a language used to great web pages . It is not a programming language it it a mark up language meaning it is used for presentation . Web browsers read the HTML code to present the webpage visually to anyone who is viewing it
What is compression
Compression is a reduction in file size so something g contains less bits of data
Why is compression important
Compression is important as when files are transferred over the internet often people have to pay for data to be sent and received . If a file is compressed it means less data is transmitted as so there is a lower cost to consumers . Also a compressed file will take less time to download
Types of compression.
Lossy compression - in lossy compression some of the information if lost the file is compressed and gets smaller in transmission. But when a file is decompressed not all data is retained . This compressed file will not be the same as the original This may be okay in audio files as it would simply reduce the quality however it would not be okay for documents as key words could be lost which may alter the meaning of the text
Lossless compression , in this compression no data is lost but storage is made more efficient which reduces file size
AAAAABBAAAAA
5A2B5A
All data is retained so the file size is the same as what it was prior to compression
File standards
JPEG / JPG - stores of complex images , small file size as lossy compression is used
GIF - creates images with a maximum of 256 colours
PDF - stores documents hat can be read in a range of devices
MP3 - used to store audio files
MPEG - used to store videos
Qualities of an algorithm.
An algorithm is a step by step process that solves a problem it must be :
Precise - so the intended outcome is attained
Well defined - have set inputs and outputs
Finite - the task has to have a clear end point
Types of algorithm
Pseudocode- this code is a mixture of computing code and regular written English . It tends to have the form of a code this it replaces the structure (indentation)
Flowchart - pictorial representations of a process
An algorithm can be split up into subtasks this can make it more manageable or means. Team can work on it
There are two things that measure the efficiency of an algorithm
Correctness - does it complete the task that is set
Efficiency - does it complete the task in the least amount of time and via the least amount of steps
Programming language
Machine code - this is the simplest form of computer code it is expressed singularly in binary in the form of bit patterns . Machine code is the raw set of instructions executed by the CPU.
High level code - these codes are like ordinary English they follow strict syntax (rules like indents) and are fairly easy to interpreted , computers cannot read high level code it must be translated to low level code in order to be processed by the computer
What is a translator
A translator is a utility program that coverts one programming language into another as we cannot generally interprets low level code
Characteristics of translators
Assembler - directly converts assembly language into machine code by converting instructions into bit patterns
Complier - translated block text to high level code can be ran and an error report may be generated
Interpretation - high level machine code . Translates line by line and stops translating of it reaches a line with an hour
IDE
IDE = intergrates development environment, it is a program that provides a collection of tools for a programmer
Editors - the IDE allows users to enter and modify computer code . It may colour key words
Error diagnostics - the IDE helps identify syntax errors any informs the program on which line the error has occurred
Run time environment - this runs the code to check for errors before it gets translated to machine code
Auto documentation - comments the code to ensure the programmer does not repeat there-self
Complier / interpreter - converts the code into machine code or can be read ran in real time
Data handling
Integer = A whole bumper
Real = a number with a decimal place
Char / character = a single letter or number for instance Y for yes
String - a combination of characters
Boolean - true or false
Computational thinking
Computational thinking is a method of problem solving where possible solution are developed and presented in ways that humans can understand
Abstraction
The process of filtering out : I processing data you do not need to focus on
Decomposition
Decomposition is producing subtasks
Syntax errors
Syntax errors are grammatical errors in programming language . A syntax error occurs when the syntax has not been ovary edited for instance if an indent is misplaced or missed
Logic error - a logic error is where the program still runs but not in the way the programmer intended it too . Logic errors are often hard to locate in code
Transcript errors - a error caused by typing on data incorrectly for instance miss spelling
End of a buss network
At the end of a bus network there is a terminator
A DBMS uses …
SQL - structured query language
