ComputersÑTools for an Information Age, 5e

ComputersÑTools for an Information Age, 5e

Conventional design Identifies functions and data structures as separate entities Then Defines those functions in more and more detail down to the level of algorithms And defines data structures like relational entities

Object-Oriented Design another paradigm Object-oriented design is based on objects and their attributes. Object Classes An object is a self-contained unit that contains both data and related facts and functions.

Objects are arranged hierarchically in classes and subclasses based on their dominant characteristics. Attributes and Methods Facts related to an object are called attributes. Methods are the instructions that tell the data what to do.

Object Inheritance An object in a subclass automatically possesses all the characteristics of the class from which it is derived. A cat is a mammal so it has the properties of mammals We do not need to say that a cat has hair because mammals have hair A mammal is an animal and has the properties of animal

We do not need to say that a cat can breed because: a cat is a mammal and a mammal is an animal So a cat is an animal And all animals can breed so a cat can breed (unless its a liger, of course) Step 4. Systems Development Up until this point, we have not used any programmers at all.

Programmers and database specialist are given the specifications and models produced in the earlier phases and must build the system This can be done using programming languages (3GLs) like C, Cobol, PL1, Java, etc

or using drag and drop development interfaces (4GLs) like Access, Oracle etc. System development includes: Scheduling Programming Testing

Scheduling Scheduling deadlines and milestones is another task of a systems project manager. Scheduling involves determining the allocation of people and resources, monitoring schedules, and producing status reports. Programming

At this point in systems development, programmers are given program design specifications and they begin to write code. The Programming Process

The steps involved in developing a program include: Define the problem Plan the solution Code the program Test the program Document the program Define the Problem

The task of defining the problem consists of identifying what it is you know and what it is you want to obtain. Plan the Solution Planning the solution may involve drawing a

flowchart or writing pseudocode, or both. Flowcharts A flowchart is a pictorial representation of a step-by-step solution to a problem. Flowchart Basics

A flowchart consists of arrows to represent direction the program takes and boxes and symbols to represent actions. Flowchart Symbols Process

Start/Stop Connector Input/Output Flow direction Decisio n Flowchart Symbols Start Deposit Show message

Get amount Valid ? No Yes Add balance & amt Show new balance 22 Pseudocode

Pseudocode is an English-like nonstandard language. It allows programmers to focus on the program logic without being concerned about the particulars of a formal programming language. Code the Program

Coding a program means to translate the logic from a flowchart of pseudocode into a programming language. The rules of computer languages are called syntax. These rules must be followed precisely. Test the Program as we go During coding, tests must be performed to make

sure the steps are correct and render the desired results. Testing includes: Desk-checking Translating Debugging Desk-checking This form of testing involves mentally checking the logic of the

program to ensure that it is error-free and workable. Translating Programs are commonly translated by a compiler which checks for syntax errors and converts the program into a form the computer understands.

Debugging Debugging means to detect, locate, and correct mistakes in the program. To find errors, you must test every part of the program under various conditions. Document the Program

A programmer must document the various stages the program has gone through as well as other specific facts about the program. Validation and Testing At every step in analysis, design and development,

we MUST check with the client and users that we understand exactly what they want.This can be done using: prototypes, structured walk-throughs, design models Once we have a working prototype, we carry out FORMAL testing Testing

Testing cannot be an ad hoc process. We must make a test plan, identifying all the components we intend to test and how we intend to test them Ideally, the system is tested with large quantities of typical data. This takes time to generate.

Test case scenarios are then carried out and the results recorded. If the results do not agree with the expected results, the process should be repeated. If the results still do not agree, we have detected a problem in the system back to coding If all the functional testing is OK we move on to user testing to see if users will do unexpected things with the system that will cause errors Step 5. Implementation

For the implementation phase to be successful, the following activities are required: Training Equipment conversion File conversion System conversion Auditing Evaluation Maintenance Training

A system will only be as good as the people who use it. Therefore, training the users is very important. Equipment Conversion Implementing a system requires that consideration has been given to how best to convert to the new

system. Issues of availability of space, accessibility, and cleanliness of the work area cannot be overlooked. File Conversion Converting old file structures to that needed by the new system can take a long time.

Care must be taken to not corrupt old files, lose files, or disrupt normal operations of the client organization during this conversion. System Conversion A systems analyst will need to determine the timing and staging of the conversion from the from the old system to the new one.

Auditing To guard against deliberate or unintentional violations in security, the systems analyst designs an audit trail. Evaluation Evaluation is needed to determine if the system is: working meeting the organizational requirements

meeting the original budget limitations Maintenance Maintenance is an ongoing activity and includes monitoring and making revisions throughout the life cycle of the system.

There is a group project due on Monday 7 Oct. WEEK 10 Unfortunately this is a public holiday so there will be no tutorial on that Monday. The group project willbe submitted to GENE at her office on Tuesday 8 Oct. instead.

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