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1.2 System design basics (10 hours)

Components of a computer system

1.2.1 Define the terms: hardware, software, peripheral, network, human resources.

Hardware: anything within a computer you can physically touch.

Software: the collection of programs and instructions that control the computer.

Peripheral: the devices attached to the computer that allow it to interact with its environment and exchange information.

Input peripherals:

Output peripherals:

Network: a group of computers connected together in some way to share resources such as documents or files and printers.

Human resources: the humans operating the computers

1.2.2 Describe the roles that a computer can take in a networked world

Client: a computer accessing resources hosted by an other computer, the server. Resources could be documents, printers, scanners etc.

Server: a computer hosting resources to be shared across the network, like documents, printers etc.

A computer can be both client and server in a network at the same time!

DNS Server: a special type of server mapping web addresses to IP addresses allowing us to surf the web without having to look up the IP address of every website they want to visit.

Router: a computer routing network packages between two networks usually using a different medium for information transfer, like phone cables or glass fibre connections.

Firewall: a computer or software package monitoring and protecting the network traffic of a computer or computer network. It decides which computers get access to the network or computer based on a set of rules. It can be looked at as an analogy to the bouncer in a disco.

1.2.3 Discuss the social and ethical issues associated with a networked world.

  • Loss of jobs due to computers because fewer secretaries are needed.
  • Through extensive networking, many business activities can be outsourced to cheaper locations, like call centres in India, leading to loss of jobs in the home country.
  • Is it ethical to fire workers from a company because a computer system has been implemented that does the same job cheaper?
  • Digital divide. Those who are confident with computers have higher chances for success than those who don’t.
  • Can an iPad and Facebook replace face-to-face social interaction?

System design and analysis

1.2.4 Identify the relevant stakeholders when planning a new system.

Who will be involved in the system?

  • Systems analyst
  • End users
  • Operators and  staff
  • S/W company

1.2.5 Describe methods of obtaining requirements from stakeholders.

Observation: involves systems analyst walking around the organisation watching how things are done with his/her own eyes. Advantages:

1.2.6 Describe appropriate techniques for gathering the information needed to arrive at a workable solution.

  • Questionnaires
  • Interviews
  • Observation
  • Current system documentation
  • User manuals

Questionnaires

 Advantages:

  • Possibility of gathering first-hand, unbiased information

 Disadvantages:

  • Often people don’t work the way they normally do when being observed

ACTIVITY Complete for the approaches to gathering information

1.2.7 Construct suitable representations to illustrate system requirements.

System flow charts: diagrams representing how different parts of the system are linked together and how the system should work in general.

Data flow diagrams: diagrams representing how information is moving through the system, together with identifying all relevant inputs and outputs to the system.

Structure charts: are diagrams representing the organization of a system, usually with showing the different parts in hierarchical order.

UML ?

1.2.8 Describe the purpose of prototypes to demonstrate the proposed system to the client.

Prototypes are abstract representations of the system, often focusing on only one or two key aspects of the system. They are important in testing as each component of the system can be tested before implementing, and to illustrate the working of the future system to the client. An example of prototyping is a shipyard building a prototype of an icebreaker ship to test out different bow designs without having to spend large money building a ship with an eventually unworkable design. Prototypes in systems development are usually ‘ghost’ user interfaces illustrating the position of control elements to the user or little programs developed to explore the working of a key algorithm in the system.

1.2.9 Discuss the importance of iteration during the design process

1.2.10 Explain the possible consequences of failing to involve the end-user in thedesign process.

1.2.11 Discuss the social and ethical issues associated with the introduction of new IT systems.

Human interaction with the system

1.2.12 Define the term usability.

1.2.13 Identify a range of usability problems with commonly used digital devices.

1.2.14 Identify methods that can be used to improve the accessibility of systems.

1.2.16 Discuss the moral, ethical, social, economic and environmentalimplications of the nteraction
between humans and machines.


SDLC Lesson Overview

Systems Development Lifecycle

Building a house

Investigation/Feasibility study

Investigate systems currently being used - benefits/limitations

requirements for the new system

Create report on

Purpose of the new system

System scope/what it will cover

Deficiencies in the current system

User requirements

Costs and benefits of the new system

Investigate

What kind of house is needed?

How will the house be used (family, young couple, retired, young single)?

How big is the plot of land?

Does the land have Gas. Water, electric?

What rooms/levels are required?

Likely cost to build the house

Benefits of the house

Analysis - Detailed User Requirements

Detailed list of

Input requirements

Output requirements

Processing and calculations required

Detailed requirement list

Rooms

Size of rooms

Requirements in each room

Type of building

Design the Systems

Work out:

Data Flow Diagrams

Entity Relationship Diagrams

Attributes

Data Dictionary

Program Specifications

Design the House

Work out:

House plan

List of parts required

Plan build of house, what needs to be done in what order

Develop the system

Write the programs according to the design

Build the house

Build the house according to the house plans and project plan

Test the system

Functional test

test each program

System test

Test programs link together correctly (whole system test)

Make sure everything works in the house

Test wiring and electrics

Test plumbing

Test heating

Test appliances in the kitchen

etc

System Documentation

Produce:

Technical Documentation

User Documentation

House Documentation

Land registry documents

Contract on sale of house

Searches

Instructions on central heating/appliances

Systems Implementation

Train the users in how to use the system

Hand over the system to the users

New Owners move into the house

Maintenance - Monitor & review

Make sure system is running okay

Report and fix any bugs in the system

On Going Maintenance

Report any problems back to the builder

Builder fixes problems


Lesson 1( 1.1.1 -.1.1.3 )  ( SDLC )

Learning Objectives

  • Overall understanding of the SDLC Stages
  • Understand Purpose and methods of data collection
  • Understand the need for change management
  • Understand the choice between bespoke / off the shelf and SaaS
  • Understand the meaning of a legacy system 


Google Doc explaining the different stages of SDLC  -  Open and Take copy  clicking here

Lesson 1 Class Activity

Select a real life example from the list of software system types below that has been a disaster. 

Provide a brief overview of the disaster and the reason why it was a disaster. You will report your findings in the next class. 

  • An embedded system (This is a system where the software controls a hardware device and is embedded in that device.)
  • Off the Shelf
  • Transactional ( web applications such as e-commerce applications where you can interact with a remote system to buy goods and services.)
  • Modelling / Simulation
  • Information system (primary purpose is to manage and provide access to a database of information. )
  • Batch processing ( Billing / payroll )
  • Data Collection system / A sensor-based data collection system ( example gathers data from environment )

Lesson  2 ( SDLC )

Learning Objectives

  • Overall understanding of the SDLC Stages
  • Understand and rank the key methods of data Collection
  • Compare the implementation of systems using a client’s hardware with hosting systems remotely.

Review Questions

When an organization needs new software what are the main options available ?  

Lesson  3 ( testing )  ( SDLC )

Learning Objectives

  • Understand the difference between Beta and Alpha testing
  • Appreciate the waterfall approach has faults  
  • Understanding of other more agile approaches

Review so far

  • 1
    Legacy System – In computing, a legacy system is a technology, computer system, or application program, that may or may not be supported/available for purchase any more.
  • 2
    Merger – A combination of two things, especially companies, into one

Activity 5-10 min Class discussion on advantage and disadvantageous  of

1 off the shelf software and

2 Custom / Bespoke S/W

Task find a SW disaster and share with class 5 mins

Stage 1 Analysis and User Requirements

  • Questionnaires
  • Interviews
  • Observation
  • Current system documentation
  • User manuals

What is the output of this stage ?

What is the big weakness in the waterfall method to s/w development?

Waterfall -  Sequential flow in one direction thus waterfall. In real life failures to correctly capture user requirements can be a disaster as the costs to change after the coding / development has started is huge 

Incremental Models

First step create part of the system with limited functionality. Example in patients record system first step provide view only access to patient records.

Stage 2  Add Amend update

Open Source would be a good example of the incremental approach 

Iterative Model

First step show interface to system options available reports etc ( do not add the actual functionality until end user approved). We are therefore clarifying the user requirements.

The user can request change with minimal additional time and cost being added to overall project budget 

What is  prototype ?

Similar to Incremental

Agile Approach 


Implementation

  • Direct changeover / Big Bang 
  • Parallel running
  • Phased Changeover
  • Pilot running

We have discussed off the shelf S/W and Bespoke 

We have looked at these stages in the waterfall methodology 

1 )Systems Analysis and defining user requirements ( Methods of data gathering).

2 )Approaches to setting the system live.

Without a proper plan on how the new system will be implemented once it is designed the change from the old system to the new one will not be successful. Many factors will need to be regarded:

  • End user training
  • User's reluctance to change
  • User acceptance testing
  • Type of change over  

Lesson  4 Overview  ( SDLC )

Learning Objectives

  • Learning with Flash Cards Click Here
  • Why Projects Fail Review Real Failure Click here
  • Overview  SDLC click here

The Systems Analyst Ethics

Lesson  5  ( User Focus Documentation and Training )

Learning Objectives

  • Describe the importance of user documentation
  • Evaluate different methods of providing user documentation
  • Evaluate different methods of giving user Training 

LInk to slide Show click here


Review Unit Test Past Papers

resources 

Legacy System Definition

A legacy system is a computer system that is no longer available for purchase or is no longer supported by the manufacturer. A legacy system might be just a few years old, or it could be decades old. Some legacy systems may operate on (and even require), certain very old hardware which is no longer available. Others may only run on older operating systems and not be compatible with modern versions. Sometimes the manufacturer of a legacy system no longer exists, and in other cases the manufacturer has dropped support in favour of more recent products. This usually means updates and security fixes will not be available for the system, which can be a significant problem for organisations.

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