3.1.2 - Software

3.1.2 - Software

1. Systems Development LifeCycle (SDLC)

   • 1. Feasibility and Problem Definition
     • Problem Definition is where you "fully define" a problem.
       • A "Systems Analyst" and the "Client" discuss the problem.
         • This ensures all the issues are fully understood by both parties.
     • Feasibility is an "analysis of the viability" of an idea.
       • This study helps to decide if the proposed idea is actually possible to carry out.
       • Questions that need to be asked in a feasibility study:
         • Technology
           • Do they have the right tech?
           • Is there tech available to complete the project?
         • Economics
           • Workers?
           • Can the company afford it?
           • Work space?
         • Would people buy it?
   • 2. Requirements
     • Refines project goals into defined functions and operations of the intended application.
     • Analyses end-user information needs.
     • A "Requirements Specification" is written.
       • This document outlines:
         • Functionality
         • External Interfaces
         • Performance
         • Attributes
         • Design Constraints
       • A "Data Flow Diagram" (DFD) is created to show:
         • External entities
           • Data source or destination.
         • Data Stores
           • Location of data.
         • Processes
           • An operation performed on the data.
         • Data Flow
           • Movement between entities, processes or data stores.
   • 3. Analysis and Design
     • Describes desired features and operations in detail.
       • Features and operations described:
         • Screen Layouts
         • Business Rules
         • Process Diagrams
         • Pseudocode
     • Data is collected through:
       • "Questionnaires"
         • Sending out questionnaires and analysing responses.
       • "Observations"
         • Observing current procedures to see how things could be more efficient.
       • "Structured Interviews"
         • Interviewing staff at different levels in the company.
     • A "Design Specification" is written.
       • This document includes:
         • Input and Output Design
         • Processing
         • Data Structure Design
   • 4. Implementation
     • This is where all the code is written.
   • 5. Testing
     • Brings all the pieces together into a special testing environment.
       • The following things are looked for:
         • Bugs
         • Errors
         • Interoperability
     • Testing is used to measure the quality of developed computer software.
     • "Systems Testing" tests a completely integrated system to verify that it meets its requirements.
     • There are many forms of testing, these include:
       • White Box
       • Black Box
       • Dry Run
       • Acceptance
     • Installation Planning
       • Installing the product.
       • Must be done collaborating with the client, not in isolation.
   • 6. Evaluation
     • Using criteria, the finished product/system is evaluated against objectives.
       • These objectives were originally agreed between the client and the analyst.
   • 7. Maintenance
     • What happens during the rest of the software's life.
       • This includes:
         • Changes
         • Corrections
         • Additions
         • Moves to different computing platforms
       • There are three forms of maintenance:
         • Corrective
           • Actions and tests to restore a defect or remove/correct a fault.
         • Perfective
           • Software maintenance to improve performance and maintainability.
         • Adaptive
           • Software maintenance performed to make a computer program usable in a changed environment.
   • Prototyping
     • Prototyping means building a working model of a new systems in order to evaluate it, test it, or have it approved before building the final product.
     • Two main types:
       • Throwaway
         • Quickly designed to show screen layouts and output formats.
       • Evolutionary
         • Where prototyping is used almost exclusively, going directly from preliminary investigations, via the prototype, to an implemented system.

2. SDLC Models

   • Waterfall Model
     • Cascading effect between phases.
     • Each phase has a well defined starting and ending point.
       • Has identifiable deliveries to next phase.
     • Developers can go back and re-work earlier stages as development progresses.
   • Spiral Model
     • Incremental approach.
     • A prototype is built and then evaluated.
       • Evaluation leads back into the Requirements phase.

3. Application Products

   • Commercial Products
     • Stock Control
       • Track quantities of stock
       • Track re-orders
     • Order Processing
       • Placing orders
       • Delivery details
       • Payment details
     • Payroll
       • Net and Gross Pay
       • Salary
       • Wage calculations and decutions
     • Process Control
       • Keeping a process within boundaries
     • Point-Of-Sale
       • Tills and checkouts
         • Supervised and non-supervised
     • Marketing
       • Advertising
       • Promotions
       • Sales
     • Computer-Aided Design (CAD)
       • Graphically oriented information
         • Design, drafting and display
     • Computer-Aided Manufacture (CAM)
       • Physical products and materials
         • Design, drafting and production
   • Generic Software Applications
     • Word processing
     • Spreadsheets
     • Desktop Publishing
     • Presentation
     • Drawing Packages
   • Bespoke Software
     • Software written to the specification of a particular organisation or customer.
     • Areas of need:
       • Government
         • Many custom built applications for specific needs.
       • Finance
         • Large Banks
         • Processing
         • Accounts
       • Commercial
         • Stock Control
         • Order and Processing Systems
   • Knowledge Base Systems
     • Computer programs that attempt to replicate the performance of a human expert on some specialised reasoning task.
     • Features:
       • Specific area of expertise
       • Rule based
       • Reasons with uncertain data
       • Delivers advice
       • Explains reasoning to the user
     • Made up of four main parts:
       • The Rule Base
         • Contains all rules that can be applied to the data.
       • The Interface Engine
         • Uses the rules in the Rule Base.
           • Searches through the Knowledge Base.
       • The Human Computer Interface (HCI)
         • Allows the user to enter data or queries.
           • Presents the results back.
       • The Data
         • Actual information relating to the Knowledge Base.

4. Operating Systems

   • Single User
     • One user at a time.
     • Each user has different rights.
     • Keeps user files separate.
   • Multi-Tasking
     • Many applications open at once.
     • Apparently running at the same time.
     • Each application is given a small slice of processing time.
     • E.g. Listening to music whilst typing an essay.
   • Batch Processing
     • Designed to take away human interaction.
       • Stops people slowing a computer down.
     • All information given before processing starts.
     • No interaction during processing.
     • Large amounts of data.
   • Real Time (Rapid Response)
     • Feedback.
     • Many sensors.
     • Immediate response.
     • Need to update files before next input.
   • Multi-User
     • All computers accessing the same information at the same time.
     • Terminals given a small time slice of processing on a server.
     • "Thin client"
   • Distributed Systems
     • File storage spread over a number of machines.
     • Access to files is sped up because multiple file requests can be processed at the same time.
       • Advantage over single file server.

5. User Interface

   • The User Interface is the way in which human users and the computer communicate.
   • Forms
     • Organise questions or options.
     • Resembles a paper based form.
     • Filled out by typing or choosing from list.
   • Menus
     • List of choices given.
     • Often touch based.
     • Choices often lead to further menus.
       • Home option on each screen.
     • Simple and restrictive.
   • GUIs
     • Input via peripheral devices.
     • Provides articulated graphical output on the computer monitor.
   • Natural Language
     • Directed by using everyday human to human interaction.
   • Command Line
     • Input is provided by typing a command string.
     • System provides output by printing text.

6. Software Utilities

   • Compression Software
     • Reduces file size.
     • Bundles files together.
   • Hardware Drivers
     • Makes hardware work.
   • Anti-virus
     • Protects a computer from viruses.
     • Removes viruses.
   • File Handlers
     • Manipulates and controls files on a computer.
   • Firewalls
     • Protects a computer from attacks or intrusions.

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