Information Systems in Business: Software

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Information Systemsin Business Software
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The Software Crisis
Computer System

• New software applications cannot be developed
  fast enough to
• Keep up with dynamic business environment
• Keep pace with rapid hardware advances
• Lag in software development limits IS
  capabilities

Hardware
Software
Computer hardware power grows roughly by a factor
of two every 18 months (Moores law), but
computer software power barely doubles in
eight years.
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The Software Crisis (continued)

• In addition to new application development,
  existing software must also be maintained (80 IT
  personnel effort towards maintenance).
• Increasing complexity leads to the increased
  potential for bugs.
• Testing and debugging software is expensive and
  time-consuming.

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Software Fundamentals

• Some basic terms
• Computer programs - sequences of instructions for
  the computer
• Stored program concept instructions written in
  programs are stored and executed by CPU when
  needed
• Programming - process of writing (or coding)
  programs
• Programmers - individuals who perform programming

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Software Instructions to the Computer

• A computer program is a series of instructions to
  a computer to execute any and all processes
• Computers only understand instructions
  consisting of electrical signals alternating
  between two states

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Software Instructions to the Computer

• Application software enables users to complete a
  particular task
• The instructions direct computer hardware to
  perform specific data or information processing
  activities that provide functionality to the
  user. This functionality may be broad, such as
  general word processing, or narrow, such as an
  organizations payroll program
• System software enables application software to
  run on a computer and manages the interaction
  between hardware devices
• e.g. loading itself when the computer is first
  turned on, as in Windows Professional managing
  hardware resources such as secondary storage etc.

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Systems software

• Operating system
• System software
• Manages and controls computer

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• Functions of the operating system
• Allocates and assigns system resources
• Schedules use of computer resources
• Monitors computer system activities
• Provides locations in primary memory for data and
  programs
• Controls the input and output devices

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Functions of the operating system

• Time Sharing
• Sharing of computer resources by many users
  simultaneously
• Multiprocessing
• Executing two or more instructions simultaneously
  in a single computer using multiple central
  processing units

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Functions of the operating system

• Multitasking
• Multiprogramming capability of single-user
  operating systems
• Virtual Storage
• Handles programs more efficiently by dividing the
  programs into small fixed or variable length

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Functions of the operating system

• Multi-tasking - What this really means is that
  the programs are taking turns with the processor.
  It allows a single user to have the spreadsheet
  and the word processor open at the same time, and
  even more. Now the user can see to copy data from
  one to the other.
• The computer must decide on how many time slices
  each program gets. The active program gets the
  most. Next is programs that are doing things but
  which aren't the foreground program. Last is
  programs that are open but aren't doing anything.
  They need a little bit of time every now and then
  to see if they are supposed to do something yet.

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Functions of the operating systemTime-Sharing
and Multi-processing

• The next step up in complexity is multiple users.
  On a network several users can be using the same
  computer or even the same program on that
  computer. This is called time-sharing.
• If a computer has multiple CPUs, it can do
  multiprocessing. Rather than a single CPU giving
  out turns to various programs, the different CPUs
  can work simultaneously. Speed increases
  immensely. Of course cost does, too!
• It is possible for a computer to use more than
  one operating system through the use of virtual
  machines. "Virtual" means it's not really there.
  But programs written for different operating
  systems are fooled into thinking their required
  operating system is present.

           
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TYPES OF SOFTWARE
Virtual Storage
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Application software

• Includes proprietary application software and
  off-the-shelf application software.
• Tailor-made application software addresses a
  specific or unique business need for a company.
• may be developed in-house by IS personnel or may
  be commissioned from a software vendor.
• Such specific software programs developed for a
  particular company by a vendor are called
  contract software. Alternatively, off-the-shelf
  application software can be purchased, leased, or
  rented from a vendor that develops programs and
  sells them to many organizations.
• Off-the-shelf software may be a standard package
  or it may be customizable. Special purpose
  programs or packages can be tailored for a
  specific purpose, such as inventory control or
  payroll.
• General-purpose application programs that are not
  linked to any specific business task, but instead
  support general types of information processing.
• e.g spreadsheet, data management, word
  processing, desktop publishing, graphics,
  multimedia, and communications.

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TYPES OF SOFTWARE
Spreadsheet Software
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TYPES OF SOFTWARE
Data Management Software
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How are Programs Understood by the Computer?
(The Language Translation Process)
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Programming Languages

• Abbreviated forms of instructions that translate
  into machine language
• New programming languages make programming easier
  for people who are not necessarily hardware
  experts

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Programming Languages (Cont.)
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First Generation Machine Languages (ML)

• Only languages computers can directly interpret
  to carry out instructions
• ML coding time-consuming and error-prone
• ML programmers concerned with hardware details
• Every computer or family of computers has its own
  ML each is machine-dependent

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Second Generation Assembly Languages

• Represent a string of 0s and 1s for machine
  language instruction
• More English-like codes shorter than machine
  languages
• Assembler translates into machine language
• Advantages of machine or assembly languages
• Programmer in control of hardware
• Programs written in low-level languages run more
  efficiently

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Third Generation Procedural Languages

• Third-generation (procedural) languages are more
  English-like than assembly languages
• Programmers focus on the procedure of the
  application problem at hand
• Some languages are standardized or portable
• Relatively easy to learn, write, and debug
• FORTRAN, COBOL, BASIC

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Fourth Generation Languages (4GL)

• 4GLs are more English-like than procedural
  languages
• Programmer only has to select an action without
  having to specify the actions formula or
  procedure
• Easy to learn and use shorter application
  development time
• PowerBuilder, SQL

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Fourth Generation Languages (Cont.)
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Visual Programming

• Languages that let programmers create field
  windows, scroll-down menus, click buttons, etc.,
  by choosing from a palette
• Appropriate code written automatically
• Accelerates work
• Microsofts Visual Basic

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MENU BAR
TOOLBAR
FORM LOCATION SIZE INFORMATION
PROJECT EXPLORER WINDOW
FORM1 NAME OF THE OBJECT
FORM
FORM CLASS OF THE OBJECT
PROPERTIES WINDOW
PROPERTIES HELP PANE
TOOLBOX
FORM LAYOUT WINDOW
FORM WINDOW
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TOOLBOX
POINTER (NOT A CONTROL)
PICTUREBOX
LABEL
TEXTBOX
FRAME
COMMAND BUTTON
CHECKBOX
OPTIONBUTTON
COMBOBOX
LISTBOX
HSCROLLBAR
VSCROLLBAR
DRIVELISTBOX
TIMER
FILELISTBOX
DIRLISTBOX
SHAPE
LINE
DATACONTROL
IMAGE
OLE
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Object-Oriented Programming (OOP)

• Emphasis on the objects involved in the task, not
  on the procedure
• In traditional programming, programmers receive
  specifications of how a program should process
  data and how it should interact with users
• An object encapsulates a data set with the code
  that is used to operate on it
• Standardized programming modules can be reused
• Applications can be rapidly developed with
  appropriate objects from an object library