Unit AS 1: Approaches to Systems
Development
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Approaches to systems development
Reasons for systems development
• explain the impact of the ‘software crisis’;
1. Software was not being developed on time
2. Software was being delivered over budget
3. Software frequently failed to meet the user requirements
4. Effective advances in hardware and software were not being used in the production of
software
5. Software systems were becoming more complex
6. Systems were difficult/expensive to maintain
7. The user interface did not match the users’ IT skills
• explain the need for software systems that meet the needs of organisations and/or individuals;
- Software is essential for solving organizational and individual problems.
- Generic packages, e.g., Microsoft Office 365, can be tailored for specific needs.
- Standardized tasks benefit from cost-effective off-the-shelf software like payroll systems.
- Highly specialized functions, like manufacturing robot arms, require custom-made software,
incurring higher costs and longer development times.
• explain the main factors affecting systems development: the user needs, time and cost;
User needs
- people using a system can become frustrated or dissatisfied with the current system if used on a
regular basis
Time
- the requirements of the business may have changed, or the business may have expanded
- technical support may no longer be available
- technological developments may make the current system outdated
Cost
- systems may be too expensive to maintain
• understand that a computer system consists of a user interface, processes and data;
Computer System
, - Consists of a user interface which allows data to be entered that requires processing and outputs
the results after processing.
User interface
- User can interact with the computer system
- User can input data
- System outputs results and information
- For example, GUI (graphical user interface) and a CLI (command line interface)
Process
- An action carried out by the computer system
- Takes raw data and converts it into information
- Results from one process may be passed on to other processes
• describe the roles of the following during systems development:
− the systems analyst;
− the project manager; and
− the programmer;
Systems Analyst
- Liaises with the client
- Carries out feasibility study to see if the software is possible or not
- Identifies the user requirements
- Undertakes fact finding
- Defines the system specification
Project Manager
- To oversee the project
- To allocate the budget
- Allocates resources- personnel, hardware, software, budget
- Identifies risks
- Reports back to the client
Programmer
- Writes the code from the module specification
- Tests the code using a test plan
- Debugs the code
- Documents the code
Analysis
• describe the purpose of analysis;
- Identify the requirements of the system
- Identify inputs and outputs of the system
- Describe the system using a DFD and a commentary
- Identify hardware and software constraints
, - Develop a data model
C+• evaluate fact-finding techniques: interviews, questionnaires, observation and document
sampling;
Observation
- Users are shadowed as they perform a particular task
- Identifies what their role entails/data required/abilities and constraints
- Reports back to the client
Interviews
- Users are asked questions on a one-to-one basis or in groups
- It may be structured or unstructured
- Follow up questions can be asked
Document sampling
- Identifies the data an organisation needs, how this data flows through the organisation
- Existing documents such as forms, invoices, receipts, orders and reports are sampled to see
how data is input, processed and output
Questionnaires
- A set of open or closed questions developed as king's key points about the current system
- A wide selection of users are asked
• distinguish between functional and non-functional user requirements in systems, such as stock
control, reservation, payroll and billing;
Functional User Requirements
- Specifies what the system must do for the specific application
- It is a function or a process E.g:
o how data is to be entered into the system
o descriptions of outputs such as queries and reports
o descriptions of operations performed by each screen
Non-functional user requirements
- Specifies an additional condition the system must meet
- It is not specific to the system itself E.g:
o the response time it will take updating a stock database.
o criteria for usability
o security and access to the system
o storage capacity
o maintainability
o frequency of backup of data
o recovery procedures
o access restrictions (levels of access ‘read only’ – Data Protections Act)
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