System life cycle by JineshGandhi

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									     Unit 2
System Life Cycle
          Topics Covered
System Life Cycle
New Approaches to design
Resources for new systems
Processing Alternatives
Goals of System Design
              System Life Cycle
Inception: Respond to idea for system
      Sketch outline of system,outpt,input and files.
Feasibility Study: Describe existing methods of
  processing information,output,input,file processing.
Study of software and hardware alternatives.
Determine feasibilty of alternatives.
Choose most optimal solution.
System Analysis: Complete analysis of existing system
  and document it. Collect data on file specifications and
  transactions.
Requirement Analysis: Repeated meeting with users to
  determine their needs and to review of design.
Design: Develop design from user requirements.
Choose new design approaches.

Specifications: Develop specifications as far as needed for chosen
  design strategy.

Programming: Develop program specifications ,modules, schedule
  and work plan

Testing: Conduct unit, Integrated and acceptance tests.

Training: Plan and conduct training programs organized by user
   section.

Conversion: Plan detailed conversion requirements and analyze the
  impact of conversion on the whole organization.

Operations: Routine maintenance and
enhancements
          New Approaches for Design

Traditional Design Approaches to custom
 System

 Application Generators allow user to see quickly
 what the system actually does.

    Advantage:

Reduce programming Time
       Application Generator
• The eGen Application Generator, also
  known as the eGen utility generates Java
  applications from a COBOL and a user-
  defined script file.
       Application Packages
Application Packages The package can
 consist of program code and hardware
 that accomplish some part of desired
 applications for eg:An org buys a package
 to maintain various employee benefits
 system and produce various reports.

Advantage :
Shorten Development Time
     Application packages
Application packages perform business-
 specific functions, as opposed to
 operating system. Most important is the
 fact that while operating system
 software upgrades are typically
 transparent to the business
 community, application package
 upgrades are not.
• Human resource management (HRM) software
  manages internal payroll, benefits, insurance,
  and other functions related to administration of
  inhouse staff.

• Customer relationship management (CRM)
  software addresses customer management
  functionality and is primarily used by customer-
  facing departments. CRM software has grown in
  popularity .
Prototyping         The prototype is model of the
  final system. It allows the user to see some
  concrete features of the system.

      2 Types of prototype

  1)Throw Away 2)Incremental(continuosly
  modified to evolve into the final application)

      Provides immediate Feedback
End-User Programming

 : A number of organizations are encouraging
 end users to write their own programs. Special
 languages and tools make this more appealing
 than it would be using procedural languages.
     Reduces demand for
 applications
 Final System
       End-User Programming
The Programming by example (PbE)
 approach reduces the need for the user to
 learn the abstractions of a classic
 programming language. The user instead
 introduces some examples of the desired
 results and/or operations that should be
 performed on the data, and the PbE
 system infers the correct abstractions
 corresponding to a program that produces
 this output.
Demands and Resources of IS Dept
      Demand                      Resource
Operating existing System    Equipment & Human
Maintenance
Enhancements                 Human
                             Equipment, Operator,
                             Programmer etc
Developing new information   HR(Clerks,Data Entry
System                       operator,System Analyst,
                             Network Administrator, System
                             Programmer(needed in large
                             installation they work with the
                             control S/W of the
                             system,Managers(Co-
                             ordinators of Sytem Operations
                             and System design)
             Processing Alternatives
Within broad cost constraints SA should design very
  flexible and user –oriented information Systems.
On-Line Processing:

  For all the systems that are online there are several
  alternatives for the underlying computer system.

The availability of low-cost H/W and the explosion in the
  availability of very powerful processors and mini and
  microcomputers have provided a major impetus for
  online systems.

Communication costs have been dropping as this industry
  becomes more competitive and technological advances
  occur.
Originally online systems were justified because of
  the need to coordinate actions at different
  geographic locations and to have fast response.
      But today costs have been reduced to the
  point that online systems are the standard for
  new designs.

An analyst in today’s environment should seriously
  consider online features for almost every system
  being developed.
    Criteria For Deciding Processing
               Alternatives
•   Physical location of the database.
•   Location for updating and accessing the database.
•   Costs for equipment and communications
•   User Reactions.
•   Management Considerations.
       Control of Management over applications
       Control of Management over processing
       Communication between subsystems
       Coordination level between subsystems
              Input alternatives
Input: Recently the trend in the information
systems has been toward collecting data as
close to its source as possible. The objective
this philosophy is to eliminate the data
transcription wherever feasible.
             This will avoid errors and reduce the
   time required to enter the data into the
   computer.
             Online interaction should be clear and
               polite.
The designer should try to avoid a cumbersome
  input command structure and emphasize natural
  response. For online data entry, the system
  should provide courteous error messages.

Messages should explain the error politely. It might
 be advisable to give no explanation unless the
 user types a question mark.

That way those familiar with the system can avoid
  tedious error message that were really designed
  for people with less experience.
          Output Alternatives
A wide variety of output alternatives are available.
The most conventional form for output is impact
  line printer. The major advantage of line printer
  is that it can make multiple copies of the same
  report using carbon paper.
              There are number of nonimpact
  printers that operate at much higher speeds.
              The primary technology is laser printer.
       Microfilm is an output medium that has been
  used increasingly for data that have to be kept
  for historical purposes.
The major disadvantage with microfilm is
 that a special device needed to read it and
 special attachments must be used to
 photocopy one frame of the film. Output
 occurs at much higher speed than printing.
Output rates in hundred-thousand
 characters per second range.
One of the other output storage media is
 image.
          Goals of System Design
1.   Understand the existing system Problem and the
     existing solution.

2.   Suggest improvement to present procedures.

3.   Assess the feasibility of using new system.

4.   Design the possible system within the limits of cost
     and technology.

5.   Plan Programming and testing of the system.

6.   Plan the complete implementation of the system.

								
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