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					Mis 4 Principles of enterprise information system
Mis 9 The architecture of computer systems


Introduction
   System is a set of interrelated elements
               A purposive system is a system that seeks a set of related goals
               Open systems interact with an environment

   Information systems
                  Minimal information systems consist of three elements: people, procedures and
                       data
                  Data is a pool of observations

   Computer information systems
              Include a computer
              Programs are instructions for computers
              Computer can serve several roles
              Data storage and retrieval device (data librarian)
              Processing capabilities
              Communication device
              Presenting information
              Computers and humans are partners in IS
              Human procedures are translated into computer programs
              Information systems need not involve computers

       Information system components:
             Two entities: human and computer
             The connection between them is in the data
             Data can be either user’s data or commands
             Data is a bridge between the computer and a human
             Both computers and humans need specific instructions


       The five components common to all IS:
              Hardware
              Programs
              Data
              Procedures
              People

Personal IS:
normally a PC, the user develops it on his own

Workgroup IS:
   PCs are connected together in Local area network (LAN)
   Programs not only process data, but also manage communications
   Department personnel do not develop WIS
Enterprise IS:
   IS is based around a centralised computer
   Programs not only process data, but also co-ordinate processing of concurrent operations

Characteristics of system types

Type              # of users              Perspective                 Roles
Personal          1                       Individual                  User
                                                                      User Operator
                                                                      User Developer
Workgroup         Many,                   Department -                User
                  but < 25                Users share same            User Operators
                                          perspective                 Professional Developers
Enterprise        Many,                   Organisation –              User
                  Often hundreds          Users have many             Professional Operators
                                          perspectives                Professional Developers



Fundamental types of IS
   Transaction processing systems (TPS)
   Management information systems (MIS)
   Decision support systems (DSS)
   Office automation systems (OAS)
   Executive support systems (ESS)

Transaction processing systems
Support day-to-day operations
       Ex:      order-entry s., accounts payable s.,
                        Payroll s., ….
Developed in the 50s in accounting depts.
The event is recorded by keying it into the computer system as a transaction
The TPS program generates two types of output:
 Messages back to the operator
 Printed documents

On-line systems : involve a direct connection between the operator and the TPS program
Batch systems : transactions are grouped and processed as a unit
Menu is a list of action choices
        Submenu is a lower level menu
Screen form is the electronic equivalent of paper forms
The TPS data is comprised of tables of data
The TPS programs add, delete, change or display values of the tables of data
Reports can be printed if desired


Management information systems (MIS)
Two very different definitions

The narrow definition:
        MIS is an IS that facilitates management by producing structured, summarised reports on a
        regular and recurring basis

Output of MIS are produced routinely and used for controlling activities

MIS are a level above TPS applications

MIS are not concerned with day-to day operations

 MIS process data that is generated by TPS or other resources TPS data are processed by
   aggregation and reformatting      Reports are automatically generated
           (on daily/monthly, etc. basis)
 MIS looks also for exceptional conditions
 Sometimes, MIS does not use TPS data directly, but their extract (for security)
 MIS may also store and maintain data for its own
 Spreadsheet program can sometimes perform MIS calculations

Decision support systems (DSS)
 DSS are interactive computer-based facilities for assisting decision making in less structured
   environment
 The need for DSS may be irregular
 Flexibility and adaptability are critical
 DSS involve models of business activity
 DSS models are often quite complex

Expert systems are the special case of DSS
 ES process input data against a knowledge base
 ES encodes knowledge that can take a human several months/years/decades to learn

Office automation systems (OAS)
 They create, store, modify, display and communicate business correspondence (in written, verbal
   or video form)
 They fundamentally change the ways that offices conduct their business
 Originally – just for stand-alone word processing

New features:
 Electronic mail
 Facsimile machines
 Voice mail
 Image processing
 Video conferencing
 Time management

 No common OAS architecture
Executive support systems (ESS)
 Support the information needs of very senior executives (very reluctant users)

   Characteristics of ESS:
   Graphical
   Easy-to-use interface (pointing devices, touch screen)
   Highly aggregated information
   Optionally expand to detail level
   Integrate many resources of data
   Timelines crucial



COMPUTER ARCHITECTURE
HARDWARE
    Categorise HW by the function it serves with regard to data:input
    processed
    stored
    output

Input hardware

Transmit data to the processing and storage HW

Input data can be in
 source form
 machine form

Devices:
 keyboard
 display screen
 mouse
 scanner
 voice recognition device
 handwriting recognition device
 bar code readers
 modem


Processing hardware

Includes devices that compute, compare and perform special instructions

Central processing unit (CPU) contains:
 control unit
 arithmetic-logic unit (ALU)
 includes registers to perform operations on data
 system memory


CPU characteristics:
Speed can be expressed in Megahertz (MHz)

System memory:
 Two fundamental types:
 Read-only memory (ROM)
            Holds initialisation instructions
            ROM contents are not lost when power is off

   Random-access memory (RAM)
             Can be both read and written
             Used for program instructions
             RAM contents are lost when power is off

Capacity of RAM (MB - GB)

Three categories of processing HW:
 Mainframe
 Minicomputers
 Microcomputers

Storage HW

Two types of magnetic storage:
        Tape
                      only sequential access to data
                      data cannot be updated in the middle of the tape
                      suitable for archiving
        disk
               hard disk
               floppy disk (diskette)

                      sequential and direct access to data
                      disk layout: sectors, tracks

Optical storage HW
 CD-ROM
 WORM (write once/read many)Erasable optical disks

Output HW

   printers
   plotters
   screens
PROGRAMS (SOFTWARE)
Program is a set of instructions that directs the general purpose computer to accomplish specific tasks

Two major groups:
 System programs
 Application programs

System programs:
             They control the computer’s resources and allocate them to other programs
             They provide the interface between HW and the other types of programs

Types:
            Operating system (OS)
                         Manages other programs’ access to CPU and to external HW
            Utility programs
                         Provide generalised services such as formatting a new disk, copying a file, etc.
            Communication control program (CCP)
            Database management system (DBMS)

Application programs
 Horizontal market applications
              Common to most industries
              Most common to PCs
              Examples: word processing, spreadsheets, DTP
              Powerful functions and features for a modest price
              Development cost can be amortised
              It never makes sense to self-develop

   Vertical market applications

                Satisfy a need specific to a particular industry
                Examples: accounting, inventory, …

 Custom-developed programs
             Applications unique to company
             Are like tailored clothing
             The time and risk make in-house development undesirable
             Two possibilities:
 Development on demand (expensive)
 Off-the-shelf programs



DATA
Data representation

Computers represent data in the form of binary digits called bits (values 0 or 1)
The group of bits that represent a character is called byte
Two character codes are common:
 ASCII-8
 EBCDIC

Bytes are grouped together to form fields or data items
A group of logically related fields is called record
A group of records is called a file

File processing

 Computer data is processed in two fundamental ways:File processing
 Database processing

With file processing data is stored and processed in separate files

Two types of FP:
 Sequential file processing
 Stores and accesses records in sequence
 Example: payroll processing

   Direct-Access file processing
   Used when Seq. Proc. is impractical
   File must be stored on disk
   Indexes must be used to determine location of a particular record


        Data integrity problem

Database processing
Database is a self-describing collection of integrated records
It contains a dictionary (directory) of its contents
It contains multiple tables of interrelated records
DBMS introduces data-independence



The Value Added by IS
Why do organisations create information systems?

Beliefs that IS have value to you

Successful IS add value appropriate to their cost in several ways:
 Can help to improve products and/or processes
 Can increase quality
 Can facilitate management
 Can help make better decisions
 Can bring competitive advantage

Processes and products
are related

Improving the process improves the product (and vice versa)

A process is a set of activities coordinated to accomplish some goal
There are hundreds of processes – not equal
IS can make process less labour intensive, more efficient, faster, more enjoyable, …
Structured activity requires little judgement, evaluation or insight
Unstructured activity needs judgement, evaluation and human creativity – it is difficult to automate

Products are output of processes (things, documents, services….)Products differ in their characteristics
and delivery

IS can enhance features of products or add new characteristics
                         competitive advantage

IS can improve the means by which products can be delivered to customers (air-line reservation
system, in-home shopping, ATM, ….)

Four ways an organisation can increase its quality

Innovation means dramatic changes:
        Discontinuity between what has been and what is now
Improvements involve adjustments rather than dramatic changes
Quality improvement depends on (requires) the concept of feedback
The quality of the output is compared to certain criteria

IS has several roles in a feedback system:
 It creates the feedback information
 It facilitates adjustment of the process (in automatic manufacturing system)
 It can perform What if ..? analysis

				
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