3.1.2 Software

3.1.2 Software

1. 3.1.2a - SDLC Introductions

   • When writing a computer program, the people involved will go through a convential set of stages
     • This is called the Systems Development Life Cycle (SDLC)
     • They include the following:
       • Requirements: Specifies the projects overall goals into the defined functions operations of the application that is being designed. Also considers the end-user needs
       • Analysis and Design: Describes the requested features and operations in specific detail, include the interface, the business rules, process diagrams, any pseudocode and other documentation.
       • Implementation: The physical coding.
       • Testing + (Installation and Planning): Brings everything together to test for errors, bugs and interoperability
       • Evaluation: Evaluation carried out of the finished product against the objectives and specifications that were requested by the user
       • Maintenance: Occurs during the remainder of the software's life. Includes changes, corrections, additions and moves to different platforms.

2. 3.1.2b - Problem Definition

   • It is essential that a problem is fully defined before it is tackled.
     • This is prevented with the aid of two people.
       • A System Analyst (Computer Technician)
       • The Client (The Customer)
       • The two are able to sit down and discuss the problem and ensure both parties fully understand all the issues.
         • This allows for the perfect solution to be coded

3. 3.1.2c - Feasability

   • It is good to know whether a program is actually possible, or feasible; before it is programmed.
     • There is no point starting a project and wasting money if it is not feasable
       • This is called the 'Feasibility Study'
         • "An analysis of the viability of an idea"
         • It focuses on asking the question of "should we proceed with the proposed project area?"

4. 3.1.2d - Gathering Data

   • During the SDLC, we need to carry out a more detailed investigation into the current problem and the requirements of the system we are trying to build
     • It is important to get the requirements phase right so that the solution can be solved properly
     • We can get data through:
       • Questionnaires
         • Sending out questionnaires and analysing responses
       • Observations
         • Observations of current operations, by spending time in various departments.
       • Structured Interviews
         • Interviewing of staff at different levels of an organisations

5. 3.1.2e - Requirements

   • At this point we can begin to write the 'Requirements Specification', which will include the following:
     • Functionality - What is the software supposed to do?
     • External Interfaces - How does it interact with people, the hardware and software?
     • Performance - Specs such as speed, availability and response time
     • Attributes - The portability, correctness, maintainability and security.
     • Design Constraints - Standards in effect, implementation language and other policies
   • The Benefits of a good requirements specification are that it becomes easy to see exactly what is needed within the software, so that all the requirements can be met.
     • The Requirements specifications will actually include:
       • Current data structures
       • Inputs and Outputs
       • Processing
   • A Data Flow Diagram can be used to show the data usage in a system. It consists of four different shapes:
     • [A RECTANGLE] External Entity - Data sources and data destinations
     • [A CIRCLE] Process - An operation performed on the data
     • [TWO SQUARES] Data Store - Such as a file held on disk
     • [AN ARROW] Data Flow- The movement between processes or data stores

6. 3.1.2f - Design

   • Once we have reached the design phase, we need to form a 'Design Specification'. It will include:
     • Output Design - This is primerarly discussed, as the output is what the system will do.
     • Input Design - What goes into the system, such as restrictions, validation and verification.
     • Diagrammatic Depiction - Diagrams showing how the system will work.
     • Processing - What needs to happen to the input to receive the output?
     • Data Structure Design - How exactly will the data be stored?

7. 3.1.2g - Evaluation

   • The system should be evaluated against the originally agreed objectives.
   • Other evaluation might include the productivity of the system analysist

8. 3.1.2h - Documentation

   • It is important to have good documentation tracked during the SDLC.
     • It might include: Technical specifications, evaluation reports, training materials, module specifications, electronics and software design documentation, standards compliance documentation, user manuals, technical manuals, maintenance manuals and installation manuals, test plans

9. 3.1.2i - Testing

   • Testing is the process that measures the quality of software in development. Tests include:
     • White Box
     • Black Box
     • Unit
     • Integration
     • Dry Run
     • Functional
     • Acceptance
   • Installation Planning is extremely important once testing has passed. Bad Installation Planning can cost thousands.

10. 3.1.2j - Maintenance

    • All software has a limited lifespan. Throughout its lifespan, constant reviews and reassessment to see where maintenance is needed occurs.
    • The different types of maintenance include:
      • Corrective
        • Maintenance carried out to ridicule a defect
      • Perfective
        • Maintenance intended to improve the program
      • Adaptive
        • Adapting the program to allow it to work in a different enviroment

11. 3.1.2k - Prototyping

    • Prototyping involves building a working model of a new system in order to evaluate and test it before building the final product.
      • There are two types:
        • Throw-away
          • Quickly designed version that gives a basic understanding. This way a look and feel can be achieved.
        • Evolutionary
          • A version which is continuously modified until the developers are happy with it as a basis for the final product.

12. 3.1.2l - SDLC Models

    • The SDLC will usually follow one of two models during it formation. They consist of:
      • The Waterfall Model
        • This model allows the developers to re-visit an earlier stage from the experience gained from the next. The start and end are also well-defined.
      • The Spiral Model
        • This model follows the stages in order, and has the evaluation feed for new requirements.

13. 3.1.2m - Applications in Business

    • There are different types of application software used in business, commerical and industry world. They include:
      • Stock Control: Track the amount of stock and re-orders.
      • Order Processing: Everything from placing orders to the delivery.
      • Payroll: Net Pay, Gross Pay, Salary and Wage Calculations
      • Process Control: Keeps a process within its boundaries.
      • Point-of-Sales: Involves tills and checkouts, both supervised and not.
      • Marketing: Systems that relate to advertising, promotion and sales.
      • CAD and CAM: Computer Aided Design and Manufacture. Allows for automated help when designing and manufacturing.

14. 3.1.2n - Generic Software Applications

    • There exist many different software applications. They include:
      • Word Processing
      • Spreadsheets
      • Desktop Publishing
      • Presentation
      • Drawing Packages

15. 3.1.2o - Bespoke Software

    • Bespoke software is when it is designed for one organsation or purpose, and will meet their specific requirements.
      • Examples of when bespoke software might be used:
        • Government
        • Finance
        • Commercial

16. 3.1.2p - Knowledge Based Systems

    • A knowledge based system is a program that attempt to imitate human intelligence in a given task.
      • Features include:
        • Limited to a specific field of expertise
        • Typically based on rule set
        • Can reason with uncertain data and output 'don't know' to a question
        • Able to deliver advise
        • Able to explain its reasoning
      • Usually made up of 4 parts:
        • The Rule Base - Contains the rules that can be applied to the data
        • The Interface Engine - The software which uses the rules and searches the data
        • The Human Computer Interface - Allows the user to enter data or queries and is able to present feedback
        • The Data - Contains the actual information related to the knowledge base

17. 3.1.2q - Operating Systems

    • An operating system is software that handles the interface to the hardware and manages resource.
      • It is needed for controlling and monitoring the running of application programs, and allows feedback to be sent to the user.

18. 3.1.2r - Types of OS

    • There are 6 main types of Operating Systems:
      • Single user
        • One user at a time
        • Each user has different rights
        • Keeps files seperate
      • Multi-Tasking
        • Can support many applications running at the same time
        • Each application is given a small amount of processing time
      • Batch Processing
        • All input is given before processing starts
        • No interaction during this process
        • Takes time before output is generated
      • Real Time
        • Displays feedback
        • Equipped with many sensors
        • Immediate response
        • Files need updating before next input
      • Multi-user
        • All computers appear to be accessing information at the same time
        • Terminals are given a small amount of processing on a server
      • Distributed System
        • File storage is spread over several machines
        • Speeds increase because multiple file requests can be processed at once

19. 3.1.2s - Batch Processing and Rapid Response

    • There are many different real life situations where these OS's are used.
      • Batch Processing
        • Billing System
        • Payroll System
        • Exam System
      • Rapid Response
        • Radar System
        • Assembly Line Robots

20. 3.1.2t - User Interfaces

    • Most software incorporates a user interface. It is the way in which the human user and the computer communicate
      • Some user interfaces include:
        • Forms: An interface used on the WWW to organise questions and options so that they resemble traditional paper based forms to the user.
        • Menu: An interface that lists choices in a touch based format. Usually includes a back and home button.
        • Graphic User Interface: Takes in input via input devices and provides a graphical output.
        • Natural Language: An interface that uses speech as the communication medium
        • Command Line: Takes in input from command strings inputted by the user. Used for administration tasks.

21. 3.1.2u - Interface Design

    • Good Interface Design is essential. Thousands is spent by companies on the HCI when developing software.
      • Questions that need to be asked:
        • Who is going to use it?
        • What tasks will it be used for?
        • Colour Scheme
        • User Instructions and help facilities
        • Forms and Drop-down menus

22. 3.1.2v - Utility Software

    • Utility software is used to manage a computer and allow it to run more efficiently. Such software includes:
      • Compression Software: Reduces file size and bundles files together
      • Hardware Drivers: Allows devices such as graphics cards and printers work
      • Anti-Virus: Protects a computer from viruses and removes them
      • File Handlers: Helps to manipulate and control files on a computer
      • Firewalls: Protects a computer from internet attacks