Applications of Computer System Flashcards
Check Sum
An error detection system. The check-sum is calculated by summing all the values in a block of data and including it when the data is stored or transmitted.
Flat File
A Flat File refers to a single file used to hold all of the data within a specific problem.
Flat File Problems
- Data redundancy.
- Data consistency
- Data integrity
Relational database
A relational database is a collection of tables that hold records. The records may be connected through relationships (links).
Data Consistency
This deals with ensuring data is accurate and valid.
Problems can arise if data goes out of date, e.g. storing age instead of date of birth.
It can also arise if the same data is stored more than once.
Data redundancy
Data items are said to be redundant if they are stored more than once. Redundancy can lead to loss of consistency.
Data Independence
Data being inconsistent in a flat file due to possibility of different formats, etc, and being consistent in a RDBMS as each record is only stored once so cannot have different attributes. A date field could be stored in file as a text field but in another field as a date/time field and the data would be incompatible. In a relational database because the attributes of any one entity are contained within one file, there is no risk of the same attribute being stored in a different format in a different file (Spelling mistakes in names).
Normalizing
Normalizing is the process of ensuring that data is correctly organized. There are three tests, called normal forms, which should be applied to the data to ensure that the data is correctly organized.
1st Normal Form
A database is in 1st Normal Form if it has no repeating attributes or group of attributes.
2nd Normal Form
A database is in 2nd Normal Form if the non key fields depend on the whole key and not part of it.
3rd Normal Form
A database is in 3rd Normal Form if data items are dependent on the (primary) key, the whole (primary) key and nothing but the (primary) key.
Primary Key
A primary key uniquely identifies a record in a file. No two records in the file will have the same primary key.
Foreign Key
A foreign key forms a relationship from a record in one entity to a record in another entity.
DBMS
A Data Base Management System is responsible for managing, storing, retrieving data, in a database, for other applications to use.
View
A view is the name given to the part of the data structure that can be seen by a particular use or application.
Transaction Support
A transaction is a sequence of events that must be carried out either completely or not at all. If the transactions fails then all of the steps carried out must be reversed.
Concurrency Support
This DBMS functions enables many user processes to access a database at the same time. In Particular, when user processes involve transactions that update the same data, a DBMS must perform at he updates in a way that prevents them interfering with each other. For example record locking.
Database Security
It covers:
- Making sure each user has access only to what they need to do their job.
- Ensuring data is not lost through hardware or software failures.
Preventing Loss of Data is managed by:
- Time back-ups
- Log/transaction files.
Query Languages
A query language is a (simple) language that allows data to be extracted from a database.
Example: SQL
SQL
Structured query language. A 4GL used to define, interrogate and manage databases.
Data dictionary
A data dictionary is a document that describes each table (file) in the database, each field in terms of data type and validation, and identifies primary and foreign keys.
Database Administrator
The database administrator manages the structure of and access to the data in a database.
Recovery
Restoring a computer system after failure. Possibly by copying files from a backup to the working store.
Distributed Systems
Distributed systems refer to the use of more than one computer in order to store or process data. This generally takes place behind the scenes so the user is not aware that more than one computer is being used.
Distributed Processing
Distributed Processing is the sharing of the processing requirements by using many computers accessed across a network. (It’s a form of parallel processing)
Distributed Processing Problems:
- Speed of data transfer.
- Not suitable for all tasks.
Distributed Database
A distributed database is one where several computers on a network each hold part of the data and cooperate to make it available to a user.
Distributed Database Benefit
It is to make the data as close as possible to the user to reduce network traffic and to speed up data transfer.
Distributed Database drawback
It is difficult to ensure that all the data in all the computers is always up-to-date/maintain integrity.
Data Warehousing
Data Warehousing is the accumulation of data possibly from several sources, for future processing.
Data Mining
Data Mining is the analysis of large amounts of data in a data warehouse to provide new information. The analysis will try to find statistically significant correlations or trends in the data.
Uses of data mining (supermarket)
- To identify unexpected shopping patterns in supermarkets.
- Optimize website profitability by making appropriate offers to each visitor.
- Identify suspicious (unusual) behavior, as part of a fraud detection process.
Uses of data mining (Insurance companies)
- Spot and understand trends in claims.
- Identify high risk customers.
- Identify customers who may not renew policy (so they can be targeted).
- Predict and detect fraudulent or risky behavior.
Problems of Data Mining
- Concerns over access to personal data.
- People being refused services e.g. insurance based on age, post code.
Data security
Refers to making sure data is not lost.
Bio-metric Security
Identifying users by measuring some aspect of the body eg Fingerprints/iris/retina/voice.
Process of bio-metric security
Take fingerprint and register on a database.
To log on - take finger print and compare it with stored prints.
If they match then let the user in.
Indexed Sequential File
An indexed sequential file is a sequential file (records are in key order). An index allows direct access to any particular record if the key is known.
Advantages of Indexed sequential file
- Rapid search since the index is in RAM.
- Key might be of different size if it’s variable length record.
Multi-Level Index
A file, which is fully indexed, where the index is so large it also has an index .
The high-level index contains the block in the low level index where the record key is to be found.
How can file become corrupted?
- Hacking - deliberate damage.
- Physical damage to hard disk.
- System error.
- Virus.
Full Backup
At regular intervals a copy of the file is made and kept secure.
Incremental Backup
An incremental backup is a type of backup that only copies files that have changed since the last backup.
Incremental Backup - Advantages
- Less storage needed.
- More often - less data lost.
- Faster.
File Generations
File generation refer to the successive backup copies made of a file that frequently change. Father, Grand father, son.
Transaction Log
A full backup is made then a log of all changes is recorded. This means that the database can be restored up to the point at which it was corrupted.
Backup Problems
The files have to not be used whilst the full backup takes place otherwise there could be inconsistencies. And most organisations want their system running 24 hours a day.
Mirroring
Mirroring stores identical data in more than one place. There are two identical copies of the database.
Mirroring protects against
Physical damage to hardware.
File Archiving
An archive is a set of files that are no longer regularly needed but are kept, securely on a separate storage system, for legal or financial reasons.
Why is it insufficient to keep all of this data on line?
It would cause the main system to get bigger, causing it to slow down.
Backups would increase in size and take longer to be created as well.
File encryption
Encryption is a security measure that makes the contents of a file unreadable without a key.
One way encryption
Using a non reversible algorithm to scrabble data.
used for encrypting passwords.
Reversible encryption
Using algorithm to scrabble data wist it is transferred or stored. On retrieval the data scrabbling is reversed.
Used for: Encrypting files before transmission, encrypting files for storage.
Public key encryption
An encryption system using two matching keys, the public key that is used to encrypt and the private key that is used to decrypt.
Compression
The process of reducing a file size without losing information (non lossy compression) or without losing important information (lossy compression).
Compression - Advantage
It reduces the time taken to transmit data and means that storage requirements are less.
Lousy Compression
Image, sound, video
Non Lousy
Everything else (that’s not image, sound and video)
Image Compression
Reducing the amount of storage needed to represent an image. May be lossy or non loss.
JPeg
JPeg is a standard which allows images to be compressed. Small errors in image are acceptable. Images can be compressed to a higher level if some errors are allowed. The amounts of compression can be controlled to allow a choice between high levels of compression or high accuracy.
Mpeg
MPeg is a standard which allows compression of moving images. It allows some errors to enable greater compression. Since successive frames are often similar only the changes from one frame to the next need to be stored.
MP3
A lossy form of compression used for sound.
Safety Critical Systems
Safety critical systems are ones that would put human life at risk if they were to fail.
Safety Critical Systems - Examples
- Air traffic control.
- Traffic lights.
- Railway control.
- Power supply control.
- Vehicle engine management.
Techniques used to make sure Safety critical system keeps working
Using CASE tools where possible - Reduces human error in coding.
Careful Design - Design Validation, using design Tools (UML).
Full and through Testing:
- Test components.
- Test full system.
- Soak testing.
Hardware Redundancy - Duplicating hardware.
Alternate Power Supplies - Uninterruptable power supply.
Staff Training - To avoid errors.
Fail Safe - If a system fails it is put in to safe state.
Weather Forecasting
Weather forecasting is achieved by modelling the earth’s atmosphere, predicting how it will change in the future
Weather Forecasting - Super Computer
- Large amounts of data is inputted from variety of sources.
- It must be processed rapidly, since out of date forecasts are of no use.
- Calculations are complex, since weather is unstable/hard to predict.
- The greater the processing power the greater the accuracy.
- May require good graphics for visual representation.
- Comparisons need to be made with large amounts of historical data.
Weather Forecasting - Super computers are needed because
- The model must run faster than real time.
- The faster the computer the smaller the cubes used to model the atmosphere can be leading to more accurate forecasts.
Weather Forecasting - data is gathered by
- Land based stations
- Balloons.
- Aircraft
- Satellites.
Weather Forecasting - Data quality
Data is rejected if it fails quality control - the data need to be:
- Within Range.
- Consistent with neighboring observations.
- Consistent with trends.
CAD
Computer Aided Design refers to using computers to create designs plans for objects from engines, to furniture to buildings.
CAD - Features
- High Accuracy
- Automated dimensions
- Geometric constructions e.g. right angles, parallels.
- Calculation of areas, volumes, etc.
- Creation of parts list.
- Determine stresses on the components.
- Libraries of standard components e.g. bolts, bricks.
CAD - Results might be used for
- Producing constructions plans.
- Stress testing.
- Animating moving components to check function.
CAD- High power computers are needed because
- Interactivity/Animation is needed.
- Working in 3D requires many calculations.
- A product may be made of thousands of sub components.
CAM (Computer aided manufacture)
Computer aided manufacture is the use of computer controlled manufacturing machines, lathes, milling machines and robots. Ideally the results from the design process CAD are sent directly to the manufacturing machines.
CIM (Computer Integrated Manufacturing)
CIM refers to having integrated computer system that cover dealing with customer orders, creating or modifying designs, ordering raw materials and components, manufacturing, assemble and invoicing.
Animation
A sequence of still images shown in succession to create the illusion of moving images.
CGI
Computer Generated Imagery. used for adding realistic images to motion picture films.
Bit map
An image represented by dots called pixels.
Pixel
A picture element. In a bit mapped image the pixel is the smallest component.
Control
Control refers to the use of a computer to automate some physical process such as controlling a washing machine, traffic lights or a driver-less for lift (used in warehouses).
All control systems must have some way of sensing what is happening in the world.
Sensors
Sensors convert some physical measurements (temperature, pressure, direction ,light level etc) into an electrical signal. Many sensors are analogue devices, some, those that detect the presence or absence of something, are digital.
Analogue sensors will not be totally accurate.
Actuators
An actuator is a device that converts an electrical signal into movement. Actuator allows a computer to open and close valve, to raise and lower a barrier, etc.
Feedback
Feedback is the use of data from sensors as an input to controlling program. The result of the previous action becomes the input which contributes to selecting the next action.
Overall Control
All control system make use of feedback. Data coming from sensors is processed, the computer makes a decision about what needs to change, the computer makes changes by using actuators, this has some effect on the world, the sensors detect this effect and the cycle repeats. Infinite loop.
Chemical Simulators
Software that mathematically models the behavior of a chemical reactions.
Aircraft control
There is a computer between the cockpit controls and the flying surfaces. The pilot gives instruction to the computer, which sends a message to the flying surfaces.
Aircraft control - Affect
- The computer can monitor the progress and ensure setting are achieved and maintained.
- The computer can override dangerous commands.
- The replacement of physical links by wiring reduces weight.
- Since stressful motions can be eliminated the aircraft need not be so strong, saves weight and fuel.
- The plane can be flown (and landed) by the auto pilot more easily than a conventional plane.
- This may mean that if the computer system fails (software or hardware) then the pilot may have little or no control over the plane.
Aircraft control- Automated take off and landing
- Can take off and land in poor visibility.
- Less delays
- Less diversions
- Saving fuel
Aircraft control - Advantages
- More efficient
- Fuel economical
- More maneuverable
- Pilot-less plane
Fly by wire
An aircraft where the controls are operated by a computer. The pilot gives instructions to the computer.
Robotics
A robot is any computer controlled device that can be programmed to carry out a variety of complex tasks that mimic human activity.
Robotics - Remote Control EXAMPLES
- Bomb Disposal robots are remotely controlled.
- Laparoscopic surgery robots enter the body and are remotely controlled to perform surgery without making a large incision.
- Ophthalmic robots can be used in eye surgery where a surgeon controls a very small, accurate robotic arm.
Robotics - Domestic EXAMPLES
Designed to perform laborious tasks.
- Vacuum cleaning.
- Lawn mowing.
- Care for the elderly (in development)
Robotics - Advantages
- Robotic systems can be used where it is hazardous for or inaccessible to humans.
- Cheaper to run in the long term.
- 24 hours operation.
- More Consistent than human.
- Don’t get tired/ill.
- Can work more quickly than human.
- Factory can run without heating/lighting
Robotics - Disadvantages
- Unemployment - assembly work.
- Public acceptance - Safety.
- Lack of common sense.
- Can’t adapt in changes (for example factory on fire).
- Won’t notice obvious/repeated errors.
- May require the factory to be rebuilt.
- Difficult to set to do a new task.
Expert Systems
Expert systems consist of facts, rules and inference engine (explains the reason).
Expert Systems - Aim
To produce a knowledge base that can be used in the same way that an expect can to make judgement and to make diagnoses.
Expert Systems - Why are they required
- Save time of human expert
- Greater availability - shortage of human experts.
- Low running costs.
- 24 Hour operation.
- Consistent.
- Not make mistakes.
- Human experts die.
Expert Systems - Medicine
General diagnostics to allow nurse to screen patients and pass on potentially serious problems to doctor.
Expert Systems - Finance
To determine the way in which share prices will fluctuate.
To predict company performance from company statistics.
Expert Systems - Production
Find an expert.
- REPEAT
- Extract the knowledge. The rules used for deduction. The intuition/feelings of the expert.
- Placing the knowledge into a knowledge base.
- Testing by comparing machine outcome with decisions made by expert.
- UNTIL satisfied with response.
Expert System - package
There are many commercial expert system packages, they are often similar to Prolog and they are usually simple for the end user. They are also comparatively inexpensive but taught Expert Systems are very expensive and often commercially protected.
Expert System - Operation.
It must be able to explain the way in which it achieved the result. It must explain its reasoning process and how it has arrived at its conclusions.
Neural Nets
A computer based on the structure of a brain.
Pairty Bit
An extra bit added to a byte of data in order to detect error in data transmission.
Version Control - Types of Versions
- Beta Versions.
- Release candidates.
- Full release (shrink wrap) version.
- Bug Fixes.
- Updates.
Threats to Computer systems
- Hardware failure
- Software failure
- Accidental operator error
- Deliberate Operator damage
- Hacking
- Virus/Trojan Horse
- Catastrophic failure (fire/explosion/flood)
Firewalls
A firewall is a piece of hardware (or software) that sits between an organisation and the internet. The purpose of a firewall is to protect the organisation network from external unauthorized access.
Disaster Recovery - Risk Analysis
What possible things may go wrong and an estimate of their likelihood.
Disaster Recovery - Preventive measures
What measures are in place to avoid disaster e.g. duplicate hardware
Disaster Recovery - Staff training
The staff training that is needed to allow staff to operate when a disaster occurs.
Disaster Recovery - Recovery procedures
What steps need to be taken to recover from a particular disaster.
Disaster Recovery - Possible strategies
- Transferring processing to a computer bureau or to a different branch.
- Daily off site backups
- Manual procedures in case of system failure.
Any plan needs to be tested to make sure it is effective, updated regularly and staff are trained.
