Transcript Introduction to Computers

Introduction to Computers
Seeram Chapter 2
Definition
Computer = a machine for solving
problems
Technical definition = a high-speed
electronic computational machine
that accepts information in the form
of data and instructions through
some input device and processes this
information with arithmetic and logic
operations from a program stored in
its memory.
Computer System
3 Main Components
– Hardware
– Software
– Computer user
Computer System
Hardware – physical components of
the machine
Software – instructions that make
the hardware work to solve problems
Users – design hardware, software
and operate the computer systems
Hardware
Input device
Central processing unit (CPU)
Internal memory
Output device
External memory or storage
Hardware
Input hardware – devices such as
keyboard
Processing hardware – CPU and
internal memory
– CPU is the brain; a control unit that
controls the activities of the computer and
an arithmetic logic unit (ALU) which
performs mathematical calculations and
data comparisons
Main memory – permanent storage for
programs that make the computer run
Hardware
Output – printer, monitor
External storage – mag tape, disks,
cd-rom
Software
Hardware receives its instructions
from the software
Sets of instructions are called
programs
3 categories of software
System software – start up computer
and coordinates activities of
hardware
Applications software – program
used to solve specific problems
Software development tools – BASIC,
FORTRAN, C++
Historical Perspectives
First generation computers (19511958) – vacuum tubes and punch
cards
– Large, slow and produced lots of heat
Second generation computers (19591963) – solid state devices
(transistors)
– Smaller, less heat, and required less
power to operate
Historical Perspectives
Third generation (1963-1970) –
Silicon chips
– Smaller, greater speed and increased
reliability.
– Multi-processing, and more applications
software
Fourth generation (1971-1987) –
large-scale integration; thousands of
circuits were set on one chip.
Microprocessor
Historical Perspectives
Fifth generation (1987 – present) –
gallium arsenide based circuitry.
Parallel processing and extremely
fast processing speeds.
Classifications
Supercomputers – CRAY-2 – large, highcapacity computers. Can process data at
extremely high speeds. Used in research,
scientific modeling, weather forecasts, and
oil exploration
Mainframe – large, high-level computers
capable of rigorous computations. Large
memory and can support many pieces of
peripheral equipment. Used at banks,
universities, large business, and
government
Classifications
Minicomputer – mid level computer
built to perform complex
computations while dealing efficiently
with a high level of input and output
from a variety of users. Often
connected in a network
Microcomputers – PC, currently as
powerful as mainframes of a few
years ago.
Computer Architecture
Refers to the structure of a computer
and includes hardware and software.
Specifically refers to the computer
systems, computer chips, circuitry,
and systems software
Types of Architecture
Complex instruction set computing (CICS)
– has many built in operations
– Includes mainframes, and microcomputers
Reduced instruction set computing (RISC)
– high level machines, SUN, IBM 6000,
Motorola 88000.
RISC is faster if memory is fast so that no
time is wasted fetching instructions
CISC is faster if memory is slow because
the same work can be done without
fetching as many instruction codes
Terminology
Serial or sequential processing –
simple form of processing data one
instruction at a time
Distributed processing – information
is processed by several computers on
a network. Separate computers that
perform different tasks
Terminology
Multitasking – computer works on
more than one task at a time
Multiprocessing – uses two or more
connected processing units. Each
processor works on a different set of
instructions. This provides increased
speed.
Terminology
Parallel processing – two or more
processors running simultaneously.
A number of processes can be
carried out at the same time
Pipelining – method of fetching and
decoding instructions. Several
program instructions are in various
stages of being fetched or decoded.
Speeds execution time
Terminology
Binary Digit (bit) = a single binary
number
– Because binary digits can be long they
are often combined into groups called
bytes.
– Memory capacity is measured in bytes
1 thousand bytes = 1 kilobyte
1 million bytes = 1 megabyte
1 billion bytes = 1 gigabyte
Binary coding schemes
People enter information into computers in
the form of characters.
The characters must be represented in
binary code so that the computer can
understand.
Two types of conversion schemes exist
– Extended binary coded decimal interchange
(EBCDID) – IBM – Mini and Mainframes
– American standard code for information
exchange (ASCII) – microcomputers
Computer Hardware
Input hardware
– Keyboard
Dumb terminals
Smart terminals
Intelligent terminals
– Non-Keyboard
Light pen
Mouse
Touch screen
Processing Hardware
Speed and power are two terms
often used to define hardware
– Speed – how fast the computer
processes data
– Power – speed + other characteristics:
storage capacity and memory size
Processing Hardware
Processing Hardware (CPU)
– Control unit – directs activities of the
computer through programs stored in
memory. Directs the flow of data
throughout the computer
– Arithmetic-logic unit (ALU) – executes
arithmetic and logic operation including
addition, subtraction, multiplication,
division, and comparisons
Processing Hardware
Register – temporary storage where
information is either discarded or
sent to internal memory
Bus or Bus Line – provides a path for
the flow of electrical signals between
units.
– The amount of data transported at a
single moment is called the bus width.
A computer with a large bus size will be
faster
Processing Hardware
Memory – called primary storage or
internal memory.
– Stores the information entered in the
computer for processing.
– Stores the program that provides the
instructions for processing the input
information
– Stores the results of the processing
Processing Hardware
Internal Memory Types
– Rom – read only memory
PROM
EPROM
EEPROM
– Ram – random access memory
Storage capacity expressed in megabytes
Output Hardware
Hard copy
– Printers
– Plotters
– Camera output
Soft copy
– CRT
Storage Hardware
Mag Tapes
Disks
Optical Disks
Laser beam writes data on the
surface of a disk by burning tiny pits
onto the disk surface. Later a lower
intensity laser is used to scan the
pits. This information is interpreted
by a photo detector which measures
the geometry and distribution of the
pits
Optical Disks
3 types
– CD-ROM – read only
– WORM – Write once read many
– Erasable Optical Disk
Made of gadolinium, terbium, or iron – a
laser beam heats a small region of
magnetized ferromagnetic film and causes it
to lose its magnetization. The region
becomes magnetized in the opposite
direction during cooling and in the presence
of a magnetic field.
Computer Software
Programming
– Languages
Machine
Assembly
Procedural
Problem oriented
Natural
Computer Software
Applications Software
– Programs developed to perform specific
tasks
Systems Software
– Operating System – controls the allocation
and usage of computer hardware resources
such as memory, central processing unit,
disk space, and peripheral devices
– System software includes at least four types
of programs
Boot strap loader
Diagnostic routines
Input/output system programs
Software Interfacing
Command Driven
– The user types in a variety of learned
commands to initiate the operations
of the system i.e. dir
– Menu-driven – user selects
commands from a menu of options
– Graphic user interface – a large
variety of icons and menus
Originally developed by Xerox (at Palo
Alto) and initially used by Apple to
develop the Macintosh.
Later became available for IBM type
computers as Window
Network Topologies
Four main types
– Bus
– Star
– Ring
– Hierarchical
Bus Network
Devices are connected so that each
device is responsible for its own
communications control.
There is no host computer or file
server
Star Network
Characterized by a host computer or
file server to which several
computers are connected.
Ring Network
The devices (mostly mainframes) are
connected to form a ring without a
host computer or file server
Hierarchical Network
Consists of a central host computer
to which other computers are
connected. These computers then
serve as hosts to several smaller
machines.
Typically a mainframe plays host to
several minicomputers which play
host to several microcomputers
Network Connectivity
Local area network (LAN)
– Computers and hardware located in the
same building
Metropolitan area network (MAN)
– Several LANs in separate buildings
across a city
Network Connectivity
Wide are network
– LANs are connected to MANs are
connected all across the country or
world = WAN
– Use Bitnet and Internet to send and
share data
The Internet
Larges computer network in
existence
Created by the US Department of
Defense to ward off attacks
against one main computing
building.
Software was created which
allowed information to be broken
down and then reassembled
– Software is referred to as
transmission control protocol/internet
The Internet
TCP
– Manages packets of information and
their re-assembly
IP
– Ensures that the packets arrive at their
appropriate remote computers
The Internet
1990 Dr. Berners-Lee developed
the world wide web (www) to
facilitate communications with
remote computers through a set of
links.
– The name web refers to his vision of
these links as a spiders web
– Dr. Berners-Lee goal was to
communicate more easily with his
colleagues by linking with their
computers.
Major Components of the
Internet
User must first access a server
computer called the internet service
provider
– The server relays the user’s message to
the internet and the internet returns
email or requested information from the
server
Web Browser
– Allows users to use a mouse to point
and click on text, drawings, and
pictures.
Internet Components
Web sites can be located with a
uniform resource locator (URL)
that must conform to a specific
format to ensure successful
communications.
– Parts of the URL
http – protocol for communication links
(hypertext transfer protocol
The ISP address or domain name –
www.unmc.edu and the final portion of
the domain name, or top-level domain,
which demonstrates the type and
Internet Components
The URL ends with path, directory
and file name
– www.unmc.edu/AlliedHealth/rste.html
Computers in Radiology
Picture Archiving and
Communications System (PACS)
main components
– Image acquisition – imaging
modalities
– Storage and Retrieval – from an
optical jukebox or tape storage
system
– Display and output – images can be
displayed on workstations
– Communication and networking
– PACS/RIS interfacing – integration
with radiology information systems