Computer Systems Ms Jennifer. Ms Jennifer Senior 4 1

Transcription

1 Computer Systems Ms Jennifer Ms Jennifer Senior 4 1

2 Systems Analysis stages and the Waterfall model Ms Jennifer Senior 4 2

3 What is Analysis? When we are very young we undergo through the process of learning by remembering things and comprehend how to use these things through application. When we start growing up we begin to analyse things and decide whether we like those things we have learnt or not. This is the process of analysis, the process of brainstorming on facts to come up with our own conclusion. Brainstorming Analysis Ms Jennifer Senior 4 3

4 A typical complete library system Contains thousands of books A functional library system must contain three databases to support the system. Book database Book ID (number / text) Title (text) Author (text) Publisher (text) ISBN (number) Fiction / non-fiction (boolean) Genre / category (text) Cost (number) Date of purchase (date) Borrower database Borrower ID (number / text) Name (text) Phone number (text) Address (text) address (text) Date of birth (date) Loans database Book ID (number / text) Borrower ID (number / text) Date of loan (date) Due date (date) Ms Jennifer Senior 4 4

5 What is the meaning of a system? A system refers to all the operations that take effect within a business or an organisation. Operations refer to all the activities done by an employee or a computer in a business or organisation. Therefore every organisation or business requires a good functional system. So how can we build (construct) a good functional system? Ms Jennifer Senior 4 5

6 If we were asked to analyse the system, what do you think would be the first step of System Analysis? Ms Jennifer Senior 4 6

7 Feasibility Study Feasibility study is the first step of Systems Analysis and it involves an accurate research on the system that we want to analyse. A typical library system research include questions, reviews, questionnaires. Typical questions that may be asked for our research include: Did you find your book? Is the library a computerized system? What happens when a new book is added to the library? What happens when the library lends a book? What happens when a librarian wants to know if a book is due? What happens when a book is overdue? Did you notice that your task at the library was part of our feasibility study? That was the first step of System Analysis. Ms Jennifer Senior 4 7

8 Systems Analysis We can construct and build a good functional system by the process of Systems Analysis. The analysis of a system is done through the following steps: 1. Feasibility study 2. System study and analysis 3. Design 4. Programming and Documentation 5. Implementation and changeover methods 6. Control and review (Testing) 7. System maintenance. Ms Jennifer Senior 4 8

9 A study of a computerized Library system Ms Jennifer Senior 4 9

10 How does a Library System work? Before we start to analyse the system we need to understand how it works. When we understand how our system works, we can start to identify possible problems. Problems may be based on operations such as slow processes (operations) for example. (Problem Selection) Processes are sub-systems of the actual larger System. When we input data in our system, we expect that the data is utilized into a process from which we deliver our desired output. Ms Jennifer Senior 4 10

11 Library System Manual System Student information is entered each time a student borrows a book. Books information is entered manually and a written loan record card is kept attached with the book. Can you imagine how many record sheets a library must have to write all the records of a library system? Computerized System Student information is retrieved from the barcode card reader of the student card. The System identifies the student because the student s information is already entered (once) in the system. Books are also identified by Book ID through barcodes. Their information is entered once (manually) in the system. Ms Jennifer Senior 4 11

12 Inputs, Processes and Outputs Input Process Output Borrower ID Process Borrower s Information Book ID Process Book Information What about Loans? Person xyz has lent a book from the Library. We can search information on a particular book by Book ID. Book ID Process Book Information plus Borrower s Information including Date of Loan and Due Date to return book. Ms Jennifer Senior 4 12

13 Design of a Library system Ms Jennifer Senior 4 13

14 Systems Design Can you imagine yourself starting a program without knowing its design and structure? The same goes with Systems Analysis. We cannot initialise programming without a clear structured design. But what is systems design and how can we develop it? What about design tools? Ms Jennifer Senior 4 14

15 Designing a new system New system requirements specifications: 1. Hardware and Software 2. Files and textbooks (books) 3. Operations we must choose the best input methods; for example: Paper Input Forms, barcodes, camera, card readers. a. On screen forms and form controls for user interface b. Data validation techniques (form checks on validity of data) c. Data verification techniques (correct dates, names) Ms Jennifer Senior 4 15

16 Designing the System Processes 1 st Process Data and File structures (Three databases: Book DB, Borrower DB and Loan DB with all their relevant field names and information) 2 nd Process Back up storage device and media. Consider how often, the size of the back up and quick access. 3 rd Process Searching for books that are overdue. Database condition statement. If Due Date is greater than Today, (Select * From Loans Where Due_Date > Today) Ms Jennifer Senior 4 16

17 Representing System Processes with Flow Charts Most Basic Shapes Start / End Other useful shapes: Sub processes Process Databases Decision Data Get Visio software, or download Smart Draw software (free) to develop your flow charts Ms Jennifer Senior 4 17

18 High Level Flow Chart (not detailed) Input Process Flow Output Ms Jennifer Senior 4 18

19 Retrieve book Information Input Process Flow Output Ms Jennifer Senior 4 19

20 1. Design a flow chart to show the process required to retrieve the Borrower s Information 2. Design a flow chart to show the process for back up data in databases. Ms Jennifer Senior 4 20

21 The development of the system based on our Systems Design Model The importance of user and technical documentation Ms Jennifer Senior 4 21

22 Programming is based on our Systems Design 1. Construct Databases 2. Design User Interface (based on chosen type of input) 3. Develop and connect user input requests with Databases. 4. Develop methods of Output. Ms Jennifer Senior 4 22

23 Documentation User Documentation Define the system s objectives (aims). Define the design with screen shots of the user interface. Explain each user key input methods and output methods. Provide technical support for troubleshooting and help functions. Reflect System Analysis Stages Technical Documentation Aims / objectives of the system. Analysis of the present system and problem selection. Proposed Solution Provide a detailed design of the system processes and databases. Define critical points of the system s development. Troubleshooting / Debugging Testing / Evaluation Ms Jennifer Senior 4 23

24 How we are going to implement the system? Different methods of system changeover. Ms Jennifer Senior 4 24

25 Changeover Methods Ms Jennifer Senior 4 25

26 System testing with different techniques and review of our new system. Ms Jennifer Senior 4 26

27 Control and review Does the new system do what it is supposed to do? Does it solve the problem that was found in the first place? Ms Jennifer Senior 4 27

28 System maintenance is as important as the system itself. Regular updates, upgrades and technical support. Ms Jennifer Senior 4 28