Computer Studies Form 3 - System Development PDF

Chapter 4 System development COMPUTER STUDIES FORM 3 – AUGUST HOLIDAY WORK Instructions Write all the notes in your exercise books No printed notes or work will be accepted 1  A system Is a set of items linked together to carry out a giv...

Chapter 4 System development COMPUTER STUDIES FORM 3 – AUGUST HOLIDAY WORK Instructions Write all the notes in your exercise books No printed notes or work will be accepted 1  A system Is a set of items linked together to carry out a given task in order to achieve one or more objectives. A system is described as being either soft or hard.  Soft systems and hard systems Soft systems – human activity are said to be soft systems. They are said to be soft because: – Their boundaries may be fluid or keep on changing. – Their goals and objectives conflict. – It’s difficult to precisely define exact measures of performance for them. Hard systems – these are systems whose goals and objectives are clearly defined and the outcomes from the systems processes are predictable and can be modeled accurately.  System classification Deterministic system – these are systems whose output are known precisely by their inputs e.g. a computer system. Probabilistic system – these are systems whose output can only be predicted but not knows precisely e.g. business and economic system organisation. Cybernetic systems – these are self controlling systems which adapt to the environment and regulate their own behaviour by accessing the feedback. They access their output and adjust the input e.g. human beings, plants systems  Characteristic of systems 7. Interdependence 1. Holistic thinking 2. Feedback 8. Sub systems 3. Control 9. Processor 4. Objectives/purpose 10.Inputs and Outputs 5. Environment 11.System Entropy 6. Boundaries  Holistic thinking and sub systems Holistic thinking – in this, a system is considered as a whole. A combination of various components that makes up a system creates a complex whole whose overall goals are more sophisticated than those of the individual components. Sub systems – a system is made up of different components (subsystem). Therefore a system does not exist in solitude but it may be a component of a large system.  Processor and objectives/purpose Processor – this is an element of a system that does the actual transformation of input into output. Objectives/purpose – objectives of a system may be real or stated. An organization should state one objective and operate to achieve another user must know the major objective of a system.  Environment and boundaries Environment – the environment is the system within an organisation operates. Environment provides a reason for the existence of the system. Boundaries – system boundaries are the external element whose changes in attitudes, behaviour and property affect their state and are affected respectively i.e. it’s the limit of system.  Interdependence and feedback Interdependence – for a system to be effective and efficient, its components or subsystems must be coordinated and linked together. Feedback – a feedback is a check within a system to see whether predetermined goals are being met. The checks are conducted on a system to determine deviation. Control and inputs and outputs Control – this is the process by which the system adapts to changes in the environment in order to give the expected level. Inputs and outputs – a system communicates with its environment by  System Entropy Entropy means decay. System ‘decay’ naturally over time, hence it slowly becomes useless to the user either due to improvement in technology, new management or change in user requirements. Therefore it must be reviewed in order to improve it or develop a new one.  Open and closed system An open system receives input from and gives output to the environment while a closed system does not interact with the environment.  Information system This is a set of persons, procedures and technologies and other resources that collects, transforms and disseminates information in the system e.g. organisation.  Purpose of information system To provide the people within an organisation with information to assist in decision making process. To provide responsive service to meet user needs. To enable sharing of information. To facilitate interaction and dissemination of data throughout the various level of organisation.  Why develop new information system? New changes in organisation – management can introduce new changes, and they have to be implement to meet the needs of the organisation. Problems in the current system – the undesirable circumstances in the current system that prevent the organisation from meeting its goal. New opportunities – if an opportunity presents itself that can enable the organisations improve its services.  Theories of system development The most common theories include: – Traditional Approach. – Rapid Application Development (RAD). – The Structured Approach.  Traditional Approach This approach relies mostly on the skills and experience of individual staff members carrying out of the project. In this approach, the manual system is replaced with a computerized one without change in overall structure of the former system. Hence the weakness of the former system are not addressed, they are forwarded to the new Rapid Application Development (RAD) RAD model evolved from the theory that business today heavily rely on information technology, hence, development and implementation of information system needs to be quick enough for the organisation to maintain a competitive advantage in the market place.  Structured Approach In this approach a system development defines a set of stages that should be followed when developing a system. Stage of system development Problem recognition and definition Information gathering Requirements specification System design System construction  Problem recognition and definition Problem recognition is the initial stage where the analyst decides if the project is really necessary to look into, and if its necessary to start a new project. In problem definition, the problem must be thoroughly defined. A through survey of the problem is undertaken by identifying the problem, understanding it, and finding out of there is a possibility of getting a solution. Before a new system is designed, a special study will be carried out to establish the costs and benefits of a new system. The study is called feasibility study. Feasibility study of a system is accessed in four ways. – Operational feasibility – Technical feasibility – Economic feasibility – Operational feasibility and technical feasibility Operational feasibility – this establishes the extend to which the users are comfortable or happy with the proposed or new system. Technical feasibility – this establishes whether the technology available is sufficient or can be upgraded for the new system. Economic feasibility and schedule feasibility Economic feasibility – it establishes whether the technology available is sufficient or can be upgraded for the new system. Schedule feasibility – it establishes whether the development of the proposed system will be accomplished within the available time.  Information gathering The system analyst gathers data about the current system and the users needs from both internal and external sources. Some of the methods used to collect or gather data include: Record inspection Interview Questionnaires Record inspection and interview The documents maintained in connection to the system are referenced. This forms a good starting point for the analyst to gain an overall insight of the existing system. Interview – this is a face to face communication between the analysts as the interviewer and the affected personnel as interviewee. The  Advantages of interview The analysts is accessible to first class information. Make interviewee feel as part of the system. Give adequate opportunity for interviewee, an opportunity to put forward opinions. Disadvantages of interview Make the interviewee feel they are being summoned by the analysts. Some interviewees give answers which are not actually proven facts but opinions. The interviewee may not fully open on some issues that may be personal. The interviewee may be suspicious of the intentions of the proposed system for fear of being displaced by Questionnaires A questionnaire is a document containing a number of standard questions set to be asked to a larger number of people in order to gather information from them. The analyst is able to collect information from several key people in the organisation who may be affected by the When the use questionnaire When limited amount of information is required from a large number of people. There is a large number of people involved in the system project. The people you need to gather information from are vastly despersed.  Advantages of questionnaires Answers filled in less tense environment. Since they are filled and returned in privacy, more sincere responses are possible. Questionnaire provides many people with the opportunity to provide input and suggestion. Questionnaire saves time especially where respondents are  Disadvantages of questionnaires It’s a slow way of facts gathering. Designing questionnaires requires expertise. Some questions can be easily misunderstood hence ambiguous replies will be received. Analysis of questionnaires requires a lot of time.  Observation This requires the observer to participate or watch closely as a person performs activities in order to learn about the system. This method gives the analysts first hand experience about the problems and expenses to the system requirements.  Advantages of observation Concepts that are too difficult for non-technical staff to explain can be observed. It helps the analysts become acquainted with operational personnel. It helps the analysts acquire ‘know how’ needed to assist in changes that have been recommended. Can correct ‘hazy’ understanding or erroneous impressions.  Disadvantages of observation It’s costly and time consuming. Staff members are not comfortable when they are being watched.  Automated method This is mostly used when actual data is required but difficult to get through interviews, observation or questionnaires. Such data is collected using devices that automatically capture data from the source. E.g. video, cameras, tape recorders etc.  Requirements specification The system analyst must come with the detailed requirements for the new system. The requirements specifications include: Output specification Input specification File/data stores Hardware and software requirements  Output specification The output specifications entails activities like generation of reports used to facilitate decision making. The output can be in the form of reports either in hardcopy or softcopy. The quality of those reports is important. Formality of reports is important so that good quality reports are produced for easy understanding.  Input specification The input to the system in necessary because the contents of the input are used to maintain the master files. The following should be considered in input specification. – The contents and volume of input. – The mode and devices of input selected. – Layout and sequence of input.  File/data stores File requirement involves making an informed decision on file required to store data and information in the system. The analyst should identify the number of files that will be needed by the system and determine the structure of each file.  Hardware and software requirements System analyst should specify all hardware and software requirements for the new system. He/she should consider: Economic factors e.g. price Operational factors e.g. reliability User friendliness.  System design This involves detailing the physical design of the system, it’s the how of the process. Once the logical design is put lined during system analysis, the analyst determines the physical design, which describes the hardware, software and operating procedures required to make system operational. Several tools are used for designing an information system. Examples are flowchart, data flow diagram, requirements.  System construction This refers to coding, installation and testing of the modules and their components such as outputs, inputs and files. The purpose of the construction is to develop and test a functional system that fulfills the business and design requirements.  Testing the system The system is tested by entering some test data to find out whether its output are as expected. The system is tested using the requirements specifications and the design specification to find out whether it meets all requirements specified.  System implementation This involves installing the system in the user’s computers, testing the installed system, converting from old system to the new one and training the users. System implementation involves: File creation and conversion. Change over. Staff training File creation and conversion This involves setting up of the master files that are to be used in the support of the new system. The setting can be either from scratch or just to convert the files that were employed in old system.  Training staff The training aim at: – Convincing the staff of the user department on the effectiveness of the new system. – Remove fear of change from them. – Enabling the staff to cope with processing task of the new system.  Methods of training Demonstration Film show Manual reference Group discussion Visits  Changeover This is the process of changing over from old system to the new system. Type of changeover – Direct changeover – Parallel changeover – Phase changeover  Direct changeover In this approach the new system commence live operation and immediately the old system is abandoned. Advantage of direct changeover – It’s a cheap method – Benefits of the new system are immediately realized. Disadvantages of direct changeover – Extremely risky – Places an organization in a do or die situation.  Parallel changeover In this changeover the operation of the old system and the new system run alongside each other. Advantages of parallel changeover – Provides a method of training in the new system. – Personnel become familiar with the new system prior to actual changeover. Disadvantages of parallel changeover – Costly to run two systems – Cross checking is difficult – Requires more staff hence more training  Phase changeover In this approach implementation is done only one part of the new system at one time or a step by step. Advantages of phase changeover – Allow the system to be implemented quickly – Less costly – Failures of the system are limited – Causes minimal disruption Disadvantage of phase changeover – Problems on ensuring that the first phase is implemented and converted.  System review and maintenance System maintenance is the adjustment and enhancement or correction of errors after the system has been implemented. The reviewing involves going through the specification and testing the system after implementation to find out whether it still meets the original specification.  System documentation consists of Report of fact finding which outlines methods used to collect data, weakness of the current system and recommendation of the current system. Requirements specification which entails the output requirements, input, hardware and software required for the new system. System flowchart which shows the overall functionality of the proposed information system. Tables or file structures depending on the approach used in system construction. Sample test data to test whether the new computerized information system is working as expected. User manual which helps the user work with the new system with minimal guidance. The manual contains information like – How to install, start the system – The interface of the system – How to carry out various tasks – Error correction and how to get help  Review questions 1 1. Define the term information system. 2. Differentiate between soft systems and hard systems. 3. List five characteristics of a system. 4. What is system control? 5. Why do we need feedback in a system? 6. Explain the tem system boundary. 7. State and explain three purposes of information systems in organisations. 8. Define the term online analytical processing? 9. Draw a well labelled diagram that depicts  Review questions 2 1. Explain three system development theories and methods. 2. State the main disadvantage of Rapid Application Development method. 3. Define the term system development lifecycle. 4. At what stage does the system change hands from the development stage to the users. 5. Highlight three circumstances that necessitate the development of new information systems. 6. Define the term feasibility study as used in system development. 7. State four methods that can be used to gather information during system development. 8. State two advantages of interview over questionnaires. 9. State two disadvantages of interview method when used for information gathering. 10.Give one example of automated information gathering technique.  Review questions 3 1. Outline the four areas that are considered during the requirements specification stage. 2. Explain at least three factors that should be put into consideration during output design. 3. State four factors that may be considered in order to design a good file. 4. Explain why it is important to consider file backup and recovery strategies during file design.  Revision questions 1 1. Outline seven steps followed in structured system development. 2. Explain three tasks that are carried out during system implementation. 3. Outline three disadvantages of questionnaires. 4. Explain the concept of proxemics in interviews. 5. Give an advantages of straight changeover over parallel changeover. 6. Define the term file conversion. 7. Differentiate between a system flowchart and a program flowchart. 8. Draw four system flowchart symbols and explain their functions.  Revision questions 2 1. Define the term “attribute”. 2. Explain the importance of using automated methods in fact finding. 3. Why is observation sometimes disadvantageous when used in fact finding? 4. State one of the disadvantages of the traditional approach in system development. 5. Outline the factors that should be considered when sourcing for hardware and software resources required for a new system. 6. Outline some of the contents of a user manual that would help the user run the system with minimal guidance.