Transcript bis - OoCities

Components of an Information
System?
• Components
– Hardware - Equipment such as computers
– Software - Instructions for the equipment
– Stored Data - Facts stored in the system
– Personnel - People who operate the system
– Procedures for the people to follow
Information Systems Functions
– Input Function accepts the input data from
outside the system.
– Storage Function retains input data and
retrieves stored data.
– Processing Function calculates and in other
ways manipulates the input and stored data.
– Output Function produces results of
processing for use outside the system.
Information and Business
Management
• Management is all the activities related
to deciding how a business functions.
• A decision is a selection among different
courses of action.
• Management decisions are of three
types:
– strategic decisions
• Usually made at the highest level
• Generally long-term decisions
Information and Business
Management (cont’d.)
– tactical decisions
• Usually made at the department or workgroup
level
• Generally short to medium term in nature
– operational decisions
• Usually made by individuals at the “front line”
• Generally short term in nature
The Need for Computer
Hardware
• Important elements of computer hardware
– speed
– accuracy
– capacity
Sources of Software
• Two main sources of software
– Packaged software – available commercially
for personal, multiple-user and networked
systems.
– Custom software – created to address very
specific requirements of the users.
Input Devices
• An input device accepts data from outside
the computer and converts it into an
electronic form the computer can
understand.
• Examples include a keyboard, mouse,
scanner, digital pen, and digital tablet.
Output Devices
• An output device converts data from an
electronic form inside the computer to a
form that can be used outside the
computer.
• Examples include a screen, monitor,
printer, and fax.
Primary Storage
• Primary storage, also called internal
storage, is the “memory”, or RAM, of the
computer.
• Primary storage, which is temporary
storage, is dependent upon continuous
electrical power. Any interruption of
electrical power causes the contents of
primary storage to be lost.
Central Processing Unit (CPU)
• The CPU, or processor, carries out the
instructions of the program. It contains circuits
that perform arithmetic and logical operations.
• Data is transferred from primary storage to the
CPU with the results sent back to primary
storage.
Secondary Storage
• Secondary storage, also called auxiliary
storage, stores data not currently being
processed by the computer and
represents permanent storage.
• Data is usually transferred to and from
primary storage.
• Examples include hard disks, floppy disks,
ZIP disks, CDROMs, and DVDs.
Magnetic Tape Storage
• Magnetic tape has a capacity of 200MB to
over 40GB.
• Data transferred to the tape via a magnetic
tape drive.
• Data on a tape can only be read
sequentially.
Two Main Parts of a CPU
• Arithmetic-Logic Unit (ALU)
– May add, subtract, multiply and divide two
number. More complex operations are
completed by using sequences of the four
basic operations.
• Control Unit
– Analyzes and executes instructions in a
program. Instructions are brought in one at a
time from primary storage.
Operating System Concepts
• An operating system is a group of
programs that manages the operation of
the computer.
• Three functions of an operating system
– process management
– resource management
– data management
Capabilities of Operating
Systems
• Multitasking is appearing to execute more
than one program at a time, though the
CPU can execute instructions from only
one program at a time.
Capabilities of Operating
Systems (cont’d.)
• Virtual memory is supplemental primary
storage (RAM)
• Programs that are too big for primary
storage will be stored in secondary
storage (e.g. hard drive) This memory that
the computer appears to have is called the
virtual memory.
• It is generally temporary in nature.
Capabilities of Operating
Systems (cont’d.)
• Virtual memory operating systems execute
large programs by dividing the program
into parts and transferring the necessary
parts of the program from secondary
storage to primary storage as needed.
• The transfer process does not require any
action by the user.
Communications Channel
Media
• Wire cables – sometimes called “copper” have
been used since the 1800s.
– Two main forms
• Twisted-pair wiring
• Coaxial cable
Coaxial cable
Communications Channel
Media (cont’d.)
• Twisted-pair wiring
– Two wires twisted together
– Most telephone lines are twisted-pair
– Can also be used for data
– Data transmission rate is slow compared to
other media
Communications Channel
Media (cont’d.)
• Coaxial cable
– Copper wire insulated with rubber and plastic.
– Used with cable television systems.
– Data transmission rate is faster than twistedpair, and more expensive, but slower than
other media.
Communications Channel
Media (cont’d.)
• Fiber-optic cables
– Bundles of glass or plastic
fibers.
– Each fiber is 1/2000 inch
thick – about the size of a
human hair.
– Data is transmitted by a
laser that pulses light
through the fiber.
– Data transmission rate is
very fast .
Channel Interface Devices
• Modems – convert digital signals to
analog signals at the origin and reverse
the process at the destination of the
signal.
– Digital to analog is modulation.
– Analog to digital is demodulation .
• Modems may be either internal or
external to the computer.
Network Topologies
•
•
•
•
Star network
Hierarchical network
Bus network
Ring network
star
bus
ring
hierarchical
Advantages of Database
Processing
• Advantages
– Duplication of data is reduch .
– Easier to process different groups of data.
– Not dependent on the organization of data
in the database – the database can be
changed without changing every program
that uses the database.
Disadvantages of Database
Processing
• Disadvantages
– Expensive.
– More vulnerable (defenseless) than file processing –
all data must be stored on the same disk; damage to
the disk means all data is lost (while files can be stored in
different disks to minimize the risk of losing data)
– Can be complex to develop – systems often involves
several applications using the same database
therefore the system development requires more
careful planning and is more time consuming than in
file processing
Data Warehouses
• A data warehouse
– A collection of data drawn
from other databases
– Contains data extracted
over time from other
databases – historical data
(most databases are not
designed to handle historical data)
The Problem-Solving Process
•
The five main activities of the problemsolving process are:
1.
2.
3.
4.
define the problem
Design the solution procedure
implement the solution procedure
test the software implementation and
correct any errors
5. Document the result
1. Telecommuting
• Telecommuting involves
“commuting” over the telephone, or
other data communications channel,
rather than commuting by
transport .
• Initially, mainly computer
professionals such as programmers
telecommuted, but now many types
of employees work this way.
1. Telecommuting (cont’d.)
• Advantages include:
– Reduced commuting costs for employees
– Reduced office space cost for employers
– Increased productivity and decreased
absenteeism
• Disadvantages include:
– Cost of setting up a “home” office
– Lack of face-to-face contact with
coworkers
Transaction Processing System
(TPS) Structure
•
Three elements of a transaction
processing system:
1. Keep records about the state of the
organization.
2. Process transactions that affect these
records.
3. Produce outputs.
Storage Function
•
•
Data in a TPS is stored in data files /
databases.
2 types of data commonly found in TPS:
1. Master data – is the main data used by the
system.
2. Transaction data – is data about the
transactions that have occurred.
3. Backup and Recovery
Procedures
• Backing up means that the data is
copied periodically to another storage
media .
• Recovery means that the backup copy
of the data can be used to re-create
the original data stored on the system.
• Without adequate backup and recovery
procedures, there is a great risk of
losing data permanently.
Information Needs for Management
Decisions (cont’d.)
• Strategic decision information tends to be
external and summarized .
• Tactical decision information tends to be
both internal and external and both
detailed and summarized.
• Operational decision information tends to
be internal and detailed.
Executive Information Needs
• While strategic level managers generally
need summarized information, sometime
they need detailed information.
• The detailed information is available
through a process called drilling down .
The Strategic Impact of
Interorganization Systems
1. Sharing of information
2. Processing between businesses in a
business alliance. (Example reservation systems)
3. Ordering products electronically with and
EDI system is less expensive
The Systems Development
Process
•
The system development process,
which also called the System
Development Life Cycle (SDLC ) is
divided into five main phases:
1.
2.
3.
4.
5.
System planning
System analysis
System design
System implementation
System maintenance
4. System Implementation
(cont’d.)
• Four methods of converting to the new
system:
– Plunge – old system is turned off, new one is
turned on.
– Phased – new system is divided into parts with
one part phased in at a time.
– Pilot – new system is installed in a part of the
organization.
– Parallel – old and new systems are used
simultaneously for a period of time.
Business Process Reengineering
• Business Process Reengineering (BPR)
involves completely redesigning the
business processes, which are groups of
activities or tasks that accomplish things
for a business.
• BPR is not gradual improvement, but
rather radical redesign of business
processes.
Controlling and Securing
Information Systems (cont’d.)
– Failure recovery procedures
• Backup and recovery procedures
• disaster recovery plan