F451 - 3.1.2 Software

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a. Describe the stages of the systems life cycle

The systems lifecycle is the most common way of solving problems using computers.

Problem Definition

- Existing problems are identified

- User requirements are identified

Feasibility Study

- Is the new system technically feasible?

- Software/hardware available?

- Is the new system economically feasible? Is it socially feasible?

- Does the staff have the necessary skills?

- Is it legal/within the data protection legislation? Is it ethically okay?

- Does it meet environmental standards?

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a. Describe the stages of the systems life cycle

Analysis

- Production of a requirements specification

- Detailing inputs needed and outputs required

- Specify user requirements

- Hardware/Software needs

- Fact Finding

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a. Describe the stages of the system life cycle

Design

- Specification of a system

- User interface designed

- Specification of data structures

- Prototyping

- Algorithms

- Files/file structure

- Input/form design

- Output/report design

- Validation procedures

- Security of data

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Describe the stages of the system life cycle

Coding/Software development

- Production of programs

- Modification of code

- Production of documentation 

Testing

- Production and carrying out a suitable testing strategy

- Production of test data 

Implementation

- Method of conversion/changeover (parallel, pilot, direct etc)

- Staff training

- Installation of hardware/software

- Setting up data/transferring data 

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a. Describe the stages of the system life cycle

Maintenance
- Debugging the system

- Modification due to changing needs

- Improving current processes

Review/evaluation

- Check system against objectives stated

- Are there any limitations? 

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b. Importance of defining a problem accurately

The client may not understand the potential of the computer system. The analyst may not understand or have detailed knowledge of the specific field of interest.

So, the analyst may product a solution which does not satisfy the client. The two must pool their information in order to ensure the 'right' problem is solved.

The analyst and client will have very different ideas of the problem. It is necessary that the problem is solved in a way such that both the client and analyst agree on.

Otherwise, the client may be unhappy and the analyst will not be paid. The analyst is an expert in use of computer systems and the client is an expert in the specific area of the problem.

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c. Function & purpose of feasibility study

The purpose of a feasibility study is to carry out initial enquiries to see if there are any reasons why the new system may not be acceptable before starting to produce it. The plan should be revised if the feasibility study highlights any problems.

TECHNICAL FEASIBILITY

- Can hardware and software be found to implement the solution

ECONOMIC FEASIBILITY

Is the proposed system possible within the budget

- Is the proposed system economic to run

SOCIAL FEASIBILITY

Is the effect on the humans involved too extreme to be allowed

- Is the prposed system environmentally sound

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c. Function & purpose of feasibility study

Function and purpose of the feasibility study continued...

SKILL LEVEL

- Is there enough skill in the workforce in order to run the new system

LEGALITY FEASIBILITY

- Does the new system meet the requirements of the Data Protection Act

TIME FEASIBILITY

- Is the proposed system possible in the give ntime period/scale

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d. Importance of identifying Requirements

d. Explain the importance of determining the information requirements of a system and describe different methods of fact finding, including questionnaires, observation, and structured interview, highlighting the advantages and disadvantages of each method

The analyst needs to ensure that he/she understands the organisation requirements of a system because otherwise the system produced may not meet requirements. Also by determining the information requirements, the analyst would ensure that the correct hardware and software is implemented.

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d. Importance of identifying Requirements

INTERVIEW

- One-to-one situation

- The interviewer can change course of questions

Advantages

- Interviewee can elaborate on points

- Clients believe they are fully involved

Disadvantages

- Time consuming

- Can give biased and often opinionated views

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d. Importance of identifying Requirements

QUESTIONNAIRE

- Many workers can have their views considered in a short period of time

Advantages

- Allows all to feel involved

- Time-saving

Disadvantages

- Does not allow for individual points

- The return is usually poor

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d. Importance of identifying Requirements

OBSERVATION OF THE CURRENT SYSTEM

- Analyst is able to see the process in action

Advantages

- See system with new eyes

- See information workers may not feel is important

Disadvantages

- Workers may not act naturally because they are being observed

- Analyst may not see 'abnormal' procedures

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e. Features of analysing requirements

e. Describe what is involved when analysing the requirements of a system, explaining the nature of the requirements specification and its content:
including current data structures, inputs, outputs and processing represented in diagrammatic form (data flow diagrams, system flow charts), identity inefficiencies/problems in the curent system

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e. Features of analysing requirements

The requirements specification is a list of all the things which the solution is intended to produce. It will also identify inefficiencies/problems in the current system. Contents include:

Input Requirements - source of the various data

- Output Requirements - identifying the destinations of the final output

- Processing Requirements - identifying ways in which data is processed

- Clients agreement to requirements - these requirements are going to be used to decide whether the solution satisfies the problem and whether or not the analyst gets paid 

The analyst would need to examine the current data structures and the relationships between them. This includes descriptions such as data type because this will dictate the form that the data will be stored in and the amount of storage sapce required for the data contained within the new system.

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e. Features of analysing requirements

The analyst will use diagrams to help in the understanding of the present system, both data flow diagrams (DFDs) and systems flow charts.

DATA FLOW DIAGRAMS - showing flow of data through a system

- Source of data

- External entities

- Data processes

SYSTEMS FLOW CHARTS - showing how parts of a system are connected

- File storage

- Input

- Output 

-Processes

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f. Design Specification

f. Describe a design specification including input design, diagrammatic depiction of the overall system, processing, data structure design and output design

- The design specification is a documentation that should contain the stages necessary to produce the final end product as the designer intended

The documentation will contain the following:

INPUT DESIGN

- Design of the user interface (input forms and menus) allowing the user to enter data, make choices and give instructions

- Data required - graphical, textual or physical?

- The hardware available - keyboards or automatic?

- The experience of the operator - CLI not always suitable

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f. Design Specification

DIAGRAM OF OVERALL SYSTEM

Through use of systems flow charts and data flow diagrams (DFDs)

PROCESSING NECESSARY/ALGORITHM

Outlines the programming methods needed to be used to process the data, normally written in pseudo-code. Advantage is that it can be used to describe an algorithm in a way that is not specific to any particular programming language

DATA STRUCTURE DESIGN

Specifications of data structures including data type and the necessary validation/verification techniques

OUTPUT DESIGN

- Report design (should inform of errors, tell on progress, display results and provide help)

- Needs to be detailed in the same way as the input designs

Example: Form of output - sound may be inappropriate

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g. Evaluating System

g. Explain the importance of evaluating the system, and how to identify the criteria usd for evaluation

CLIENT

- Need to be sure the system will perform as required

- Identifies areas where the solution is lacking

ANALYST

- It determines the end of the job

- It determines when the analyst gets paid

Criteria used for evaluation, as far as analyst is concerned, is to prove to the client that the solution works and meets all the requirement spec. Criteria should include:

SUITABILITY - can the new system carry out all the requirements that were set, does the new system integrate with the existing software?

EFFECTIVENESS - is it an improvement on the existing system, is it cost effective, does the system suffer form bugs, is the hardware/software reliable?

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g. Evaluating System

USABILITY - is it easy to use, is the new system compatible with the existing systems, do the users require continious training, is the online help/tutorials useful?

MAINTAINABILITY - is the system easy to maintain?

- What limitations are there in the system?

- What enhancements could be made to the system in the future?

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h. Documentation

h. Explain the content and importance of different types of documentation at different stages of the systems lfie cycle, including the technical and user manuals

TECHNICAL DOCUMENTATION

- Designed for a future system developer/computer literate

- Very valuable for the maintenance process becuase the documentation shows how each part of the system has been constructed and the reasons why certain choices have been made

- Purposes of technical documentation:

- Allows debugging of programs

- To assist future software developments

- To modify existing file/data structures

- To support new technical staff

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h. Documentation

h. Explain the content and importance of different types of documentation at different stages of the systems lfie cycle, including the technical and user manuals

TECHNICAL DOCUMENTATION

- Designed for a future system developer/computer literate

- Very valuable for the maintenance process becuase the documentation shows how each part of the system has been constructed and the reasons why certain choices have been made

- Purposes of technical documentation:

- Allows debugging of programs

- To assist future software developments

- To modify existing file/data structures

- To support new technical staff

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h. Documentation

Technical Documentation continued...

The technical documentation should include:

Data Flow Diagrams - showing flow of data through a system

Systems Flow Chart - showing how parts of a system are related

- Entity Relationship Diagrams (ERD) - shows how data tables relate to each other

- Annotated Program Listing - the program code will be fully annotated to explain to the reader the purpose of the each section/line of code

Structure Charts/Pseudo-code/Algorithm designs

- Data Dictionary - the field definition (including data type, field length, validation techniques)

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h. Documentation

Aimed at the end user

Should accompany the system and is for the person who will actually be using the system. It provides the user with basic instrucyions about how to use the system. It will contain instructions relating to the users' view of the system and would therefore be written in a language appropriate to the users' ability rather than in computer jargon. The user documentation should include:

- Input/Output Procedures

- Index/Contents

- Glossary of terms within the documentation

Backing up and archiving procedures

- Error messages - details on possible errors and how to deal with them

FAQ - Frequently Asked Qurstions

Maintenance of files/File searching

- Required hardware specifications

- Instructions on how to operate the system

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h. Documentation

Aimed at the end user

Should accompany the system and is for the person who will actually be using the system. It provides the user with basic instrucyions about how to use the system. It will contain instructions relating to the users' view of the system and would therefore be written in a language appropriate to the users' ability rather than in computer jargon. The user documentation should include:

- Input/Output Procedures, Index/Contents, Glossary of terms within the documentation

Backing up and archiving procedures

- Error messages - details on possible errors and how to deal with them

FAQ - Frequently Asked Qurstions

Maintenance of files/File searching

- Required hardware specifications

- Instructions on how to operate the system

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h. Documentation

Aimed at the end user

Should accompany the system and is for the person who will actually be using the system. It provides the user with basic instrucyions about how to use the system. It will contain instructions relating to the users' view of the system and would therefore be written in a language appropriate to the users' ability rather than in computer jargon. The user documentation should include:

- Input/Output Procedures, Index/Contents, Glossary of terms within the documentation

Backing up and archiving procedures

- Error messages - details on possible errors and how to deal with them

FAQ - Frequently Asked Qurstions

Maintenance of files/File searching

- Required hardware specifications

- Instructions on how to operate the system

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h. Documentation

Aimed at the end user

Should accompany the system and is for the person who will actually be using the system. It provides the user with basic instrucyions about how to use the system. It will contain instructions relating to the users' view of the system and would therefore be written in a language appropriate to the users' ability rather than in computer jargon. The user documentation should include:

- Input/Output Procedures, Index/Contents, Glossary of terms within the documentation

Backing up and archiving procedures

- Error messages - details on possible errors and how to deal with them

FAQ - Frequently Asked Qurstions

Maintenance of files/File searching

- Required hardware specifications

- Instructions on how to operate the system

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i. System Testing/Installation Planning

IMPORTANCE

- The importance of system testing is to ensure that the system satisfies the user's requirements and to discover any errors that might be present. In simple terms, to ensure that the system works. The analyst would need to provide proof that the system does as required because if successful, the analyst will get paid.

- Systems testing also decide how the new hardware will be introduced, whether or not existing staff will need to be trained and the methods in which data files will be transferred from the old system to the new one.

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i. System Testing/Installation Planning

METHODS OF CHANGEOVER

Parallel - old system and new system operate together for a period of time, doing the same processing. Results from both will be compared and the odl system will only be fully replaced when the issues/erros regarding the new system have been resolved. Parallel conversion allows an organisation to revert to the odl system if the new system fails. However, this is very expensive and should only be done in situations where data is very valuable.

Direct - The old system is fully removed and discontinued and the new system replaces it completely and immediately, at a quiet time such as weekends and overnight. There is no overlap time between the systems and no part changeover. If the new system fails, the old system cannot be used.

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i. System Testing/Installation Planning

METHODS OF CHANGEOVER

Parallel - old system and new system operate together for a period of time, doing the same processing. Results from both will be compared and the odl system will only be fully replaced when the issues/erros regarding the new system have been resolved. Parallel conversion allows an organisation to revert to the odl system if the new system fails. However, this is very expensive and should only be done in situations where data is very valuable.

Direct - The old system is fully removed and discontinued and the new system replaces it completely and immediately, at a quiet time such as weekends and overnight. There is no overlap time between the systems and no part changeover. If the new system fails, the old system cannot be used.

Pilot - The new system is implemented but only in one area of the organisation. The software is running in a real situation to help identify and resolve errors before the rest of the organisation converts to the new system. This method of conversion allows staff to be trained and if a major fault occurs, only one branch of the business is affected. If succesfful, the new system is rolled out; if unsucessful, the new system is abandoned.

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i. System Testing/Installation Planning

i. System testing and Installation planning continued...

Phasing - The old system is gradually replaced, in stages, by the new system. This allows for testing of the new system to be done and allows for the gradual retraining of the staff.

INSTALLATION STRATEGY

- Method of implementation - parallel/pilot/phased/direct

Training program must be devised

Hardware must be brought and installed

- System must be tested with real data files by users

- Writing the technnical documentation

- Data files must be adapted/reformatted from present files

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j. Maintenance

j. Explain the purpose of maintaining the system, and explain the need for system review and reassessment, understanding that software has limited life span

Maintenance is the process of making improvements to (or modifying) a system that is in use. System review and reassessment is needed because:

Bugs/errors are discovered in the software code - these bugs will have been identified only after the system is in full use. They will be 'fixed' and a 'patch' would be issued that changes the appropriate lines of the code within the end-users' program.

The user requirement may change - this often happens after a system has been in operation for some time and the user sees further uses of the data that the system produces (changing user needs).

Some in-built parameters change - e.g VAT rate (legal requirements)

- Hardware is changing - the system will need to be updated to take advantage of new hardware developments. This could be a new input device, output device, or even communications device. 

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j. Maintenance

j. Explain the purpose of maintaining the system, and explain the need for system review and reassessment, understanding that software has limited life span

Maintenance is the process of making improvements to (or modifying) a system that is in use. System review and reassessment is needed because:

Bugs/errors are discovered in the software code - these bugs will have been identified only after the system is in full use. They will be 'fixed' and a 'patch' would be issued that changes the appropriate lines of the code within the end-users' program.

The user requirement may change - this often happens after a system has been in operation for some time and the user sees further uses of the data that the system produces (changing user needs).

Some in-built parameters change - e.g VAT rate (legal requirements)

- Hardware is changing - the system will need to be updated to take advantage of new hardware developments. This could be a new input device, output device, or even communications device. 

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j. Maintenance

Maintenance continued...

Operating System needs upgrading - the system will need to be modified to take advantage of the additional capacities of the OS.

Performance needs improvement - some of the original code may contain seberal unnecessary routines that are slow to execute and need 'tidying up'. Systems performance can often be improved by finding more efficient algorithms for such routines.

There are 3 types of maintenance:

- Corrective Maintenance - to correct bugs/errors found in software when being used

- Perfective Maintenance - to improve performance of software

- Adaptive Maintenance - to alter software vecayse of external need such as:

A change in user requirements, change in law, change in proccesses such as VAT change or to take account of new technologies. 

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k. Describe Prototyping

k. Describe prototyping to demonstrate how a solution will appear

prototype is a simplified version of a program to illustrate a feature of the software

Normally used to illustrate input and output screens

The screens are dummies in that they elicit no action

Used to show the client the way the system iwll look in order to gain a clear idea of the system

Allows issues/errors to be spotted

The client is part of the design process in order to give more focused feedback

Prototypes are evaluated and repeatedly refined until client is satisfied

Advantages:

Produced very quickly

- Check that end user/client is happy with the system

- More focussed feedback

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k. Describe Prototyping

k. Describe prototyping to demonstrate how a solution will appear

prototype is a simplified version of a program to illustrate a feature of the software

Normally used to illustrate input and output screens

The screens are dummies in that they elicit no action

Used to show the client the way the system iwll look in order to gain a clear idea of the system

Allows issues/errors to be spotted

The client is part of the design process in order to give more focused feedback

Prototypes are evaluated and repeatedly refined until client is satisfied

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k. Pros and Cons of Prototyping

Advantages and disadvantages of prototyping...

Advantages:

Produced very quickly

- Check that end user/client is happy with the system

- More focussed feedback

Disadvantages

- Takes up development time, especially is process is repeated

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l. Spiral and Waterfall models

l. Describe the spiral and waterfall models of the systems life cycle

SPIRAL MODEL

- Analyst begins by collecting data followed by each of the other stages leading to evaluation, which will lead to a return to data collection to modify results

- The different stages are refined each time the model is worked through

WATERFALL MODEL

- Progress is seen as flowing-steadily downwards (like a waterfall)

- Results from one stage are used to inform the work on the next stage in the cycle

- At any stage, it may be found necessary to return to re-evaluate a previous stage

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m. Common Applications

m. Identify the features of common applications found in business, commercial and industrial applications: e.g. stock control, order processing, payroll, process control, point-of-sale systems, marketing, computer-aided-design (CAD), and computer-aided-manufacture (CAM)

STOCK CONTROL

Keeping track of stock

Recording stock levels

- Database has entry for each ID number

- When stock is scanned, the ID number is found in the database

- Number in stock field is...

Incremented if goods are coming into the warehouse

- Decremented if goods are leaving the warehouse

- Therefore, number in stock field is always up to date with what is in the warehouse

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m. Common Applications

m. Identify the features of common applications found in business, commercial and industrial applications: e.g. stock control, order processing, payroll, process control, point-of-sale systems, marketing, computer-aided-design (CAD), and computer-aided-manufacture (CAM)

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m. Common Applications - Stock

STOCK CONTROL

Keeping track of stock

Recording stock levels

- Database has entry for each ID number

- When stock is scanned, the ID number is found in the database

- Number in stock field is...

Incremented if goods are coming into the warehouse

- Decremented if goods are leaving the warehouse

- Therefore, number in stock field is always up to date with what is in the warehouse

Condition of stock

Keeping track of where stock is going

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m. Common Apps - Stock Control

STOCK CONTROL

Keeping track of stock

Recording stock levels

- Database has entry for each ID number

- When stock is scanned, the ID number is found in the database

- Number in stock field is...

Incremented if goods are coming into the warehouse

- Decremented if goods are leaving the warehouse

- Therefore, number in stock field is always up to date with what is in the warehouse

Condition of stock

Keeping track of where stock is going

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m. Common Applications

ORDER PROCESSING

- If quantity in stock falls below a pre-determined limit...

- The system automatically institutes a reordering process

- When goods are delivered, the ordering system is informed so that the live order can be shown to have been fulfilled

PAYROLL

- Records are processed all at the same time

- at regular intervals (e.g. once a week)

- requires no human intervention during the processing

- payroll run once workers have gone home

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m. Common Applications

ORDER PROCESSING

- If quantity in stock falls below a pre-determined limit, the system automatically institutes a reordering process and when goods are delivered, the ordering system is informed so that the live order can be shown to have been fulfilled

PAYROLL

- Records are processed all at the same time

- at regular intervals (e.g. once a week)

- requires no human intervention during the processing

- payroll run once workers have gone home

- large amounts of data needs to be processed

- data is similar in nature, requiring similiar processing

- no need for instant responses to input

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m. Common Applications

ORDER PROCESSING

- If quantity in stock falls below a pre-determined limit, the system automatically institutes a reordering process and when goods are delivered, the ordering system is informed so that the live order can be shown to have been fulfilled

PAYROLL

- Records are processed all at the same time

- at regular intervals (e.g. once a week)

- requires no human intervention during the processing

- payroll run once workers have gone home

- large amounts of data needs to be processed

- data is similar in nature, requiring similiar processing

- no need for instant responses to input

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m. Common Applications

PROCESS CONTROL

- Automatically controls a process

- Computer receives information about the process from sensors, and data from the sensors allow the system to make decisions

- Results of decisions are actions that are carried out and the next set of inputs from the sensors are compared with the last set of inputs to decide whether the actions that were taken last time had any impact

E.g. Rolling Process

Computer stores parameters between which the thickness is acceptable

Actual thickness input at regular intervals from the sensors, actual thickness compared with stored values. If acceptable then the process is repeated. If thickness is different to stored values, then the roller is adjusted

Feedback - If roller is adjusted, next input is compared to previous input to see if adjustment has an effect

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m. Common Applications

PROCESS CONTROL

- Automatically controls a process

- Computer receives information about the process from sensors, and data from the sensors allow the system to make decisions

- Results of decisions are actions that are carried out and the next set of inputs from the sensors are compared with the last set of inputs to decide whether the actions that were taken last time had any impact

E.g. Rolling Process

Computer stores parameters between which the thickness is acceptable

Actual thickness input at regular intervals from the sensors, actual thickness compared with stored values. If acceptable then the process is repeated. If thickness is different to stored values, then the roller is adjusted

Feedback - If roller is adjusted, next input is compared to previous input to see if adjustment has an effect

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m. Common Applications

POINT OF SALES SYSTEMS

Identifies goods being bought

- Reads the barcode on products and ID searched in database

Carry out processing required

- Accumulates total value of all the goods and produces a printout for the customer (till receipt)

Arranges for payment

- Made electronically

MARKETING

Process where potential customers are made aware of a product or service

- Produce advertising mayerial and product promotional material

- Through the internet or through direct mailing

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m. Common Applications

POINT OF SALES SYSTEMS

Identifies goods being bought

- Reads the barcode on products and ID searched in database

Carry out processing required

- Accumulates total value of all the goods and produces a printout for the customer (till receipt)

Arranges for payment

- Made electronically

MARKETING

Process where potential customers are made aware of a product or service

- Produce advertising mayerial and product promotional material

- Through the internet or through direct mailing

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m. Common Applications

Computer Aided Design (CAD)

Use of a computer system to design a commodity/product

Software can be used to do calculations

Can be used to make decisions about the way the product is manufactured

Can be used to cost a solution and make predictions

Computer Aided Manufacture (CAM)

Use of a computer system to help with the manufacturing process

The design would be produced by computer controlled robots

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n. Generic Applications

n. Identify and justify generic applications software for particular application areas, e.g. word processing, spreadsheets, desktop publishing (DTP), presentation software, drawing packages

WORD PROCESSING

Write letters to customers

Process reports

SPREADSHEETS 

To keep records of sales

Calculate invoices

Make automatic calculations

DESKTOP PUBLISHING (DTP)

Producing of a manual (e.g instructions manual)

Used for producing brochures/leaflets/flyers

Produce high quality graphics

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n. Generic Applications

n. Identify and justify generic applications software for particular application areas, e.g. word processing, spreadsheets, desktop publishing (DTP), presentation software, drawing packages

WORD PROCESSING

Write letters to customers and process reports

SPREADSHEETS 

To keep records of sales

Calculate invoices or make automatic calculations

DESKTOP PUBLISHING (DTP)

Producing of a manual (e.g instructions manual)

Used for producing brochures/leaflets/flyers

Produce high quality graphics

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n. Generic Applications

PRESENTATION SOFTWARE

Used for producing multimedia presentations for an audience

DRAWING PACKAGES

Used for producing adverts/leaflets/flyers

DATABASE

To store fules of customers and sales or to manipulate customer/stock files

GRAPHICS

To create images

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n. Generic Applications

ADVANTAGES of Pre-written (generic) software

Shared development costs that make the software cheaper to buy

Immediately/readily available

Ready pool of trained workers

Most of the bugs would be missing as software will be fully tested

Compatible with software from other organisations

Third party user documentation available/online help available

There may also be training material accompanying software

Staff may already know how to use the software

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o. Custom-written Applications

ADVANTAGES of Custom-written software

Written specifically for the particular purpose needed by the business

Designed to do exactly what the user needs/fits user requirements exactly

Application is 'one off'/unique and does not fit normal crtieria for standard software

Generic software will not exist

Contains all the features that the business needs including non-standard ones

Does not contain excess functionality

Program maintenance may be easier

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p. Knowledge-based Systems

p. Describe the characteristics of knowledge-based systems

A knowledge-based system is a computer system where all the expert human knowledge covering a particular topic is brought together and made available to the user through a computer system which uses the facts it has been given in order to answer queries from outside the system.

Restricted to a narrow area of knowledge because human knowledge is so vast that it would need massive areas of data

Results cannot be given within any degree of accuracy

How is a knowledge-based system setup?

Experts in the field are interviewed

Information needs to be collected from many sources

This information is used to create the knowledg base

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p. Knowledge-based Systems

continued...

The rules use to interrogate the knowledge are collected in the rule base. 

The set of algorithms used to tell the rules in the rule base to interrogate the knowledge base are stored in the inference engine. 

HCI is setup to provide communication outside of the knowledge-based system

KNOWLEDGE BASE - Contains the information supplied to the system by the experts

RULE BASE - Contains the rules that can be applied to the knowledge

INFERENCE ENGINE - This uses the rules in the rule base and searches through the knowledge base

HUMAN COMPUTER INTERFACE (HCI) - Allows for queries to be inputted and results to be output

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q. Purpose of the Operating Systems

An OS is a suite of programs designed to manage the hardware of the system

Used to control the hardware of the system through software like hardware drivers and system software

Used to provide a platform on which applications can run and deals with issues that the software may have (e.g. storage of files)

Provides a user interface with the operator to allow communication between the user and hardware. The specific type of user interface depends on the circumstances

Handles communications using protocols to govern the communication

Handles translation of code using compilers and interpreters

Has many utility programs used to carry out housekeeping tasks on the system

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r. Types of Operating Systems

r. Describe the characteristics of different types of OSs and their uses

BATCH OPERATING SYSTEMS

Data is collected and input into the system over a period of time

Inputs are stored as a 'job' to be processed later and collected into 'batches'

Processing occurs when all input has been collected

Therefore, there are large amounts of data to be processed

Processing is carried out from beginning to end without human interaction

There is no need for instant responses to input (not time sensitive)

Data is similiar in nature and requires similiar processing

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r. Operating Systems

REAL-TIME OPERATING SYSTEMS

Data is processed instantly and the system responds instantly to changes in input

Therefore, the output affects the next input and occurs before the next input

The computer must respond within a set time limit

SINGLE-USER OPERATING SYSTEMS

Allows one user at a time to use the system

Allocates each user with rights

Keeps user files separate

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r. Operating Systems

MULTI-TASKING OPERATING SYSTEMS

Allows more than one task to run simultaneously

Use of separate windows for each task and each task is given an amount of processing time before going on to the next

E.g. play music whilst typing an essay

A typical PC is described as multi-tasking because more than oen task will be apparently running simultaneously

DISTRIBUTED SYSTEMS

File storage or processing is shared between different computers at different locations which make up the entire system

Users will be unaware of the exact physical location of the data that they're accessing

Speeds up access to fules because there is no single space where all the information must pass through

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s. Batch Processing

s. describe a range of applications requiring batch processing, and applications in which a rapid response is required

BATCH PROCESSING

Optical Mark Reading (OMR)

Multiple choice OMR forms - e.g. multiple choice exams

- Scripts are batch processed

- Scripts are processed incredibly quickly

- All processing is similiar in nature and data is of similiar type

- Large amounts of data to be processed

- Scripts are rejected if they cannot be read

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s. Batch Processing

Produce bills for customers

- Data collected over a month and similiar data is collected

- Processed at a convenient time normally at a quiet time

- Results are not needed immediately and no need for human intervention

Payroll

- Inputs are stored and collected over the course of one week because inputs are only useful when full week of values are collected

- Payroll run once a week all at the same time

- No need for humans to be present and runs when workers have gone home

- All processing is similiar in nature and data is of similiar type

- Large amount of data to be processed

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s. Batch Processing

RAPID RESPONSE

Airline booking system

- When a seat has been booked on a flight, the system needs to be updated before the next transaction (input) occurs in order to avoid the possibility of a double-booking

Missile Guidance

- Various sensors detect altitude, latitude, speed etc.

- Constantly providing up-to-date information to the guidance system

- If the missile  is slightly off course then adjustments must be made immediately

- A one second delay could result in the missile hitting the wrong target

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s. Batch Processing

Temperature/Pressure Control

- E.g. sensors in a nuclear power station will be providing data on the current temperature of the reactor

- If the reactor starts to overheat, then initiating cooling will have to happen instantly to avoid a potentially dangerous situation

Process Control

- In the manufacturing process, 1000s of signals per second can arrive from sensors attached to systems being controlled

- As such systems are fast moving, the response time would need to be extremely minimal

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s. Batch Processing

Temperature/Pressure Control

- E.g. sensors in a nuclear power station will be providing data on the current temperature of the reactor

- If the reactor starts to overheat, then initiating cooling will have to happen instantly to avoid a potentially dangerous situation

Process Control

- In the manufacturing process, 1000s of signals per second can arrive from sensors attached to systems being controlled

- As such systems are fast moving, the response time would need to be extremely minimal

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t. User Interfaces

t. identify and describe the purpose of different types of user interface

FORM-BASED INTERFACE

Characteristics

- Has specified areas for data input (input/text boxes)

- Has a cursor which moves to the next box to be filled in

- Provides lsit of alternative responses through drop-down list

- Use of radio buttons and check boxes to enter data

- Cursor shows position of next input box to be filled in and would move to it

- Cursor may not move until data has being supplied to important boxes

- Checks input is sensible/help button available

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t. User Interfaces

Form based Interface continued...

Why use it?

- Computer outputs prompts and the user responds

- Presents user with an on-screen form in which data can be viewed or entered

- Clear instructions to prompt user

- Makes sure information is input in the correct order (standard format)

- Simplified validation process - fixed options of drop-down menus

- Very few errors on input and ensures no necessary information is missed

When is it used?

- Travel agents and other booking systems

- Workers taking orders over the telephone

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t. User Interfaces

MENU-BASED INTERFACE

User interface which obtains input from the user by displaying a list of options - the menus - from which the user indicates his/her choice by using a sequence of key presses or by using a mouse. This may lead to further menus.

Why use it?

- Simple/easy to use - requires no specialist knowledge

- Limit on choice - menus restrict options/restricts user, user may be computer illiterate

When is it used? - systems that require touch screen

- ATMS - cash machines

- Mobile Phones

- Tourist information system (Avoids need for additional peripherals like a mouse and suitable for environment-provides an enclosed system with protection against vandals and the weather)

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t. User Interfaces

GRAPHICAL USER INTERFACE

User uses a device like a mouse to move a pointer and press a button over an icon. The mouse can be used to control windows or frames on the screen. 

Features:

WINDOWS

- bounded areas of screen within which different tasks can be running

-  screen is organised as a series of windows/overlapping frames

- windows can be minimsied/maximised/resized or moved and allows multi-tasking

ICONS

- small graphical image to allow easy recognition of apps

- can be pointed and clicked on and used as a shortcut for the user

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t. User Interfaces

Features of GUI continued...

MENUS

- The listing of options form which the user may select features/options

TOOLBAR

- Combination of buttons. Each button has an icon/letter depicted as an option

- Situated on the screen and used in conjunction with a mouse

DIALOGUE BOX

- To allow the user and the computer to interact in a controlled manner

- Allows the computer to control what the user is doing

- By oferring a limited number of choices such as 'yes/no/cancel'

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t. User Interfaces

Features of a GUI continued (2)..

POINTERS

- Allows for simple navigation. Usually controlled by a mouse. Used to select appropriate options

Benefits

- GUIs are intuitive

- Easy to use/navigate - online help available

- No commands/instructions have to be learnt/necessary

- Easy execution of commands - 'drag and drop' / 'point and click'

Drawbacks

- Requires more processing power and system resources

- Can be restrictive for more experienced user

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t. User Interfaces

NATURAL LANGUAGE INTERFACE

Allows user to interact with computer using a human language such as English

Operated via use of microphone or keyboardd

E.g. Expert Systems

Benefits: 

- User may find use of a natural syntax easier

Drawbacks:

- OS has to try and interpret what the yser has requested however there is a problem because the English language is full of ambiguities.

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t. User Interfaces

COMMAND LINE INTERFACE

User interface that involved typing commands for the OS via a keyboard for specific tasks

Least user-friendly and can only be used by a computer literate

Allows most direct control of OS

Task can be performed quickly by entering commands directly - need not follow a sequence of menus or windows to get desired options

Uses: Technician needing access to the whole system OR Computer programming

Benefits: Low processing power and system resources required AND experts able to perform complex tasks using single commands quickly

Drawbacks: Difficult for an inexperienced user - requires the user to learn a large range of text-based commands and their uses AND Easy to make mistakes-syntax of command is vital, instructions will not execute if the command is typed incorrectly.

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u. Importance of a good UI Design

u. Discuss the importance of a good user interface design

Form of output

- Sound may be inappropriate

- Sound must be minimal otherwise in emergency situations it will be ignored

Volume of Data

- If large amounts, operator might miss seeing some information

- Information must be ordered

- Danger of information overload, leading to omissions

- Information must be prioritised as only some data is crucial

- Information must be presented in such a way that it has immediate impact

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u. Importance of a good UI Design

Importance of a good user interface design continued...

Colours Used

- Must be enough contrast to make information readable

- Sensible use of colours like red for danger

- Must be consistent

Experience of the Operator

E.g. CLI not suitable for inexperienced operator

Operator Disability

- To ensure that disability is not an issue

- Is the operator colour blind/deaf/capable?

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u. Importance of a good UI Design

Importance of a good user interface design continued (2)...

Hardware Choices

- Suitable for both user and environment to be used in

Layout

- Information spread around the screen

- Important information in top of screen

- No overload

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v. Utility Software

v. Identify and describe the purpose of a range of utilities

COMPRESSION SOFTWARE

Reduces size of files by cutting out much of the duplication of data in the stored material but maintain the content of the files

Used to speed up transmission fo data from one place to another

Files are decompressed using a decompression algorithm at the destination

HARDWARE DRIVERS

Contains the instructions to the OS for using a peripheral

Used to configure hardware

E.g. would be used when a new printer was bought in order to install communications protocols to the OS

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v. Utility Software

v. Identify and describe the purpose of a range of utilities continued...

ANTI-VIRUS SOFTWARE

Continually looking out for the characteristics of a virus

It will delete any viruses that the software finds

FILE HANDLERS

Set of programs that manage data storage

Allows files to be searched, stored, accessed, altered, deleted, merged, sorted, ordered, renamed or copied

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v. Utility Software

v. Identify and describe the purpose of a range of utilities continued (3)...

BACK UP UTILITY

Automatically makes copies of files

To prevent loss of  files

Protects important work by ensuring that backup copies are made on different hardware devices at regular intervals

Incremental backups should be made

ERROR CHECKING SOFTWARE

Used to check that data has not been corrupted after data transfer from one part of the system to another

Often error checking software iwll automatically correct errors

E.g. echoing back or parity checks

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