Systems Development Life Cycle(SDLC) - Phases And Activities Involved

Phase 1: Preliminary Investigation

1.1 Initial analysis( nature, scope, objective )
1.2 Feasibility study(economical, operational, and technical)
1.3 Suggest alternative solution( maintain, upgrade, change )
1.4 Initial report-( submit report to executives…..make decision to do or not)
 

Phase 2: System Analysis

2.1 Gather Data( Interview, questionare, sampling, observation)
2.2 Data Analysis( check list, carta grid, data flow, break down functions )
2.3 Report writing( about the present system, problem, need for a change)

Phase 3: System Design

3.1 Prepare few system designs( based on cost, technical, operational expertise, describe the new system as a collection of modules or subsystems.)
3.2 Select the best system( security, flexsibility, …prototype)
3.3 Report writing( cost and effect)

Phase 4: System Development

4.1 purchase software
4.2 purchase hardware
4.3 System is tested at various levels.

Phase 5: Implementation

5.1 Change to new system
5.2 Train the users
5.3 Evaluate the system

Phase 6: Maintenance

6.1 check smooth flow of system operation
6.2 improve system where necessary
6.3 conducting maintenance and enhancements as determined by periodic reviews

Duties of Personnel in System Development

Conceptual for Duties of Personnel in System Development

Information systems managers

-coordinate all the activities in IS
-responsible for the running of the system

Systems analysts

-determine the requirement for the IS according to the organisation

-analyse the input to the system

-do feasibility study

-help design in develop new system

Programmers

-analyse the requirement study from the system analyst and start the implementation phase.

End users

-non-information-system professionals in an organization.

-responsible in testing the developed system and then give feedback to system analyst.

Organisation of Files

Sequential files
When records are arranged physically in a certain order, the file is said to be a sequential file.
-when the file is updated, it is necessary to go through the entire file
-sequential organization would make sense when many records need to be read or modified.
-all records have the same size and the same field format and the records are sorted in the file according to the content of a field called key.
-the files can be saved both on a disk or on a tape.
-disadvantage : Adding or deleting records become physical.

Random files
Records in a file can be accessed directly without reference to the other records in the file 
-provides a much faster access.
-the records can be scattered over the disk space in any order.

Indexed files
The rows are stored either sequentially or non-sequentially 
-an index is created that allows software to locate individual rows.
Index – a table used to determine the location of rows in a file that satisfy some condition.

Types of Information System

1.Transaction processing system (TPS)

A TPS collects and stores information about transactions, and controls some aspects of transactions. A transaction is an event of interest to the organisation.

A TPS is a basic business system. It:

·         serves the most elementary day-to-day activities of an organisation;

·         supports the operational level of the business;

·         supplies data for higher-level management decisions.

·         mostly for predefined, structured tasks

·         can have strategic consequences (eg airline reservation system)

·         usually has high volumes of input and output

·         provides data which is summarised into information by systems used by higher levels of management

·         need to be fault-tolerant.

On-line transaction processing: A transaction processing mode in which transactions entered on-line are immediately processed by the CPU.

2.Management information system (MIS)

converts TPS data into information for monitoring performance and managing an organisation. Transactions recorded in a TPS are analyzed and reported by an MIS.

They have large quantities of input data and they produce summary reports as output. Used by middle managers. An example is an annual budgeting system.

 3.Decision support system (DSS)

helps strategic management staff (often senior managers) make decisions by providing information, models, or analysis tools. For support of semi structured and unstructured decisions (structured decisions can be automated). Used for analytical work, rather than general office support.

They are flexible, adaptable and quick. The user controls inputs and outputs. They support the decision process and often are sophisticated modeling tools so managers can make simulations and predictions.

4.Expert system (ES)
a computer system or program that uses artificial intelligence techniques to solve problems that ordinarily require a knowledgeable human. The method used to construct such systems, knowledge engineering, extracts a set of rules and data from an expert or experts through extensive questioning. This material is then organized in a format suitable for representation in a computer and a set of tools for inquiry, manipulation, and response is applied. While such systems do not often replace the human experts, they can serve as useful adjuncts or assistants.

Expert systems imitate human experts in many different fields of expertise. Such systems contain rules (such as decision tables) that help a human answer expert questions.

Advantages of expert systems:

·         The computer can store far more information than a human.

·         The computer does not 'forget', make silly mistakes or get drunk when it is most needed.

·         Data can be kept up-to-date.

·         The expert system is always available 24 hours a day and will never 'retire'.

·         The system can be used at a distance over a network.

5. Executive information System(EIS)

A type of management information system to facilitate and support the information and decision- making needs of senior executives by providing easy access to both internal and external information relevant to meeting the strategic goals of the organization.commonly considered as a specialized form of a Decision Support System

emphasize on graphical displays and easy-to-use user interfaces. offer strong reporting and drill-down capabilities.

Generally, it is a enterprise-wide DSS that help top-level executives analyze, compare, and highlight trends in important variables so that they can monitor performance and identify opportunities and problems. 

The purpose was to package a company’s data and to provide sales performance or market research statistics for decision makers, such as financial officers, marketing directors, and chief executive officers, who were not necessarily well acquainted with computers.

Advantages :

ž  -Easy for upper-level executives to use.

ž  -Provides timely delivery of company summary information.

ž  -Information that is provided is better understood.

ž  -Filters data for management.

ž  -Improves to tracking information.

ž  -Offers efficiency to decision makers.

Disadvantages :

ž  -System dependent.

ž  -Limited functionality, by design.

ž  -Information overload for some managers.

ž  -Benefits hard to quantify.

ž  -High implementation costs.

ž  -System may become slow, large, and hard to manage.

ž  -Need good internal processes for data management.

ž  -May lead to less reliable and less secure data.

Data Integrity

-the assurance that data is consistent and correct.
-term that can mean ensuring data is "whole" or complete
-the condition in which data are identically maintained during any operation
-the preservation of data for their intended use

Data Validation

-the confirmation by examination and the provision of Objective evidence that the particular requirement for a specific intended use are fulfilled.
-a process by which a procedure is evaluated to determine its efficiency and reliability. (to demonstrate that a method is suitable for its intended purpose)

Data Dictionary /Language

Data Dictionary
Provides detailed accounting of all tables found within the user/designer-created database
-contains (at least) all the attribute names and characteristics for each table in the system
-contains metadata—data about data
-sometimes described as “the database designer’s database” because it records the design decisions about tables and their structures

Data Definition Language (DDL)
Used to built data, define data types and data structure in a database.
-describes the records, fields, and "sets" making up the user Data Model

Data Manipulation Language (DML)
Is that of SQL, which is used to retrieve and manipulate data in a Relational database. Comprises the 'SQL-data change' statements, which modify stored data but not the schema or database objects
-have their functional capability organized by the initial word in a statement, which is almost always a verb. In the case of SQL, these verbs are:

SELECT 

INSERT 

UPDATE 

DELETE

Database Component

Entity

Something that can be identified in the users’ work environment, something the users want to track (person,place,thing or event)

Entity set or Entity Class
The collection of all Entities/Entity Instances

Attributes
Describes the Entity’s characteristics

Weak Entity
An entity that cannot be uniquely identified by its attributes alone.
-must use a foreign key in conjunction with its attributes to create a primary key.
-the foreign key is typically a primary key of an entity it is related to.
-cannot exists without another entity.
-for example, before employee dependents can be recorded, the employee must exist first

Strong Entity
An entity type is strong if its existence does not depend on some other entity.
-has a Primary key which can be used to uniquely identify its attributes
-entity can stand alone.

Primary Key
A unique key to identify a row or a tuple.
-must never contain redundant attributes 

-can never be a null value

Composite Primary Key
Composition or combination of Primary Key

Candidate Key
When any attribute or combination of attributes that could serve as a primary key is not selected to be the primary key, than that attribute or combinations of attribute that will function as a primary.

Secondary Key
Finding a specific row without using the primary key by only using other attributes.
-handy when using large database 

-non primary search key is secondary key

Foreign Key
Relationship between tables is established through the use of a foreign key.
-the primary key of one table, put into the table of another entity.

Data Hierarchy

CHARACTERS -> FIELDS -> RECORDS -> FILES

Characters - are represented by a byte which is a combination of 8 bits.

Fields - are combinations of one or more related characters or bytes and is the smallest unit of data a user can access.

Records - are groups or related fields. A key field, or primary key, is a field that uniquely identifies each record in a file.

Files - are collection of related records stored on disks like hard disks or CD-ROMs.

Characteristic of Good Data

Accurate – error free. Inaccurate information can lead to incorrect decisions.

Verifiable – can be proven as correct or incorrect. For example, a ticket agent at an airport usually requests some type of photo identification to verify that you are the person named on the ticket.

Timely – able to get it when needed.

Organised – arranged to suit the needs and requirements of the decision maker.

Accessible – is available when the decision maker needs it. Having to wait for information may delay an important decision.

Relevant – has meaning to the person who receives it. Most information is important only to certain groups of people.

Cost-effective – should give more value than it costs to produce.

Information System Terminology

Information System also referred to a database.

Database
-designed to offer an organized mechanism for storing, managing and retrieving information. They do so through the use of tables
-database tables consist of columns and rows. Each column contains a different type of attribute and each row corresponds to a single record.

Database management system (DBMS)

A set of computer programs that controls the creation, maintenance and the use of the database of an organization and its end users.

Data

Data with regards to database is :
A collection of unprocessed items which can include facts or details about people, places, things, events or concepts.

Information
Information with regards to Database is :
Data which has been processed OR data or raw materials which has been manipulated and organized in such a way to render it useful to the user as required.

IS - Introduction

A combination of information technology and people's activities using that technology to support operations, management and decision-making. The software that we're using in this chapter is Microsoft® Office Access 2007.

Happy Learning.

:)

System Unit - Part 1

Expansion Slots:
-An opening, or socket, on the motherboard that can hold an adapter card
-With Plug and Play, the computer automatically configures cards and other devices as you install them

Ports:

-A socket on the outside of the system unit that is connected to an expansion board on the inside of the sy

stem unit.
-Connect peripheral device through a cable to the computer system
-Consist of 2 types:-

>>serial port:

#Transmits one bit of data at a time
#Connects slow-speed devices, such as mouse, keyboard, modem

>>parallel port:
#Connects devices that can transfer more than one bit at a time, such as a printer

Generation of Computer

First Generation:

Period: 1940-1956

Technology: Vacuum Tubes
Language: Low level language

-Machine Language(which only read binary value 0/1)

Size: Huge size(Occupied one whole room)

Advantage/Disadvantage:

-Vacuum tubes create a great amount of heat, thus easily burnt out.
-Very expensive to operate

-Use a great deal of electricity

Example: UNIVAC & ENIAC

Vacuum Tube

ENIAC

Second Generation:

Period: 1956-1963: 

Technology: Transistors
Language: Low level language

-Assembly language (instructions in words)
Size: Large size
Advantage/Disadvantage:

-Transistor generate heat too but not as much as vacuum tube

-Transistor cost cheaper, smaller size, energy efficient and more reliable than vacuum tube

Example: -

Transistor

Third Generation:

Period: 1964-1971

Technology: Integrated Circuits
Language: High level language

-3GL(programming language designed to be easier for a human to understand)
Size: Smaller size than 1st Gen. and 2nd Gen.
Advantage/Disadvantage: 

-An IC consist of thousands of transistor

-Transistors were miniaturized and placed on silicon chips, called semiconductors
-smaller and cheaper than their predecessors

Example: Language used -Fortran, COBOL

Integrated Circuit

Fourth Generation:

Period: 1971- Present

Technology: Microprocessors
Language: High level language

-4GL(typically non-procedural and designed so that end users can specify what they want without having to know how computer processing is to be accomplished)
Size: Able to fit in the palm of the hand
Advantage/Disadvantage: 

-Thousands of IC combined into a microprocessor

-Development of Graphic User Interface(GUI), mouse and handheld devices

-PC can form network(development of Internet)

Example: 

-Language used - Borland C++, Visual Basic

-IBM & Macintosh

Microprocessor

IBM first Microcomputer

Fifth Generation:

Period: Present and Beyond

Technology: Artificial Intelligence

Language: Advanced level language
Size: Mini size

Example: ASIMO by Honda

Asimo

Information Communication Technology (ICT) Terminology

Computer: 
An electronic device that is of high-end technology used to solve everyday problems of users. It consists of input, output, process and storage. It interprets and executes instruction and data given by the user and converts them into information.

Information Technology(IT):
Use of technology to gain/obtain/understand/ manipulate data /to execute and to distribute information.

Data:

Raw materials that are collected in the form of numbers, alphanumeric, text, sounds, videos etc. Data by itself does not bring any meaning to the user. Therefore, it needs to be manipulated in order to gain any form of understanding.

Information:

Data that has been processed/manipulated/organised in a systematic way

Knowledge:

The use of the information in a useful way.

Technology:

An application of the knowledge with the use of machinery.

Information System:
A set of interrelated components that sense, communicate, analyze, and display information for the purpose of enhancing our perception, understanding, control and creative ability.

FORM 6 COMPUTING NOTES - INTRODUCTION

Is your impression of computing limited to the study the component in a computer or its software? It seemed like every Hollywood movie depicts computing lessons as one which involves fixing a problematic computer. Well, it is not entirely wrong, but it does not show the whole picture. Computing encompasses more than that and it focuses on the computer science with regards to the study of history of the development in computer, Multimedia, Information System Development(database) and programming. So, for new computing students in Form 6, Recently would like to share with you some teasers on the subject of computing.