Transcript Data Communications and Computer Networks CIS 454/554 Instructor: Sanchita Mal-Sarkar

Data Communications and
Computer Networks
CIS 454/554
Instructor: Sanchita Mal-Sarkar
Computer
• An electronic machine that accepts input,
processes data, stores data, and produces
output.
• Data can be numbers, text, images,
graphics, and sound, etc.
• Computer program is a set of instructions.
Without it computer is useless.
• Programming languages allow us to write
these instructions (e.g. C, C++, Java, etc).
Computer system
• A computer system consists of a computer, peripheral
devices, and software.
• The computer itself can take care of the processing
function, but it needs additional components, called
peripherals, to accomplish its input, output and storage
functions.
• Example of an internal peripheral device is hard disk
drive.
Computer Hardware
• Hardware is the physical component of a
computer.
• Hardware is the equipment used to perform
the necessary computations.
• Examples:
Main memory (RAM, ROM), secondary
memory (hard disk drive, floppy disk drive),
CPU, input devices (keyboard and mouse),
and output devices (monitor and printer).
Hardware Components of a Computer System
Central Processing Unit (CPU)
• Arithmetic-Logic Unit
• Control Unit
Input Devices
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Secondary Storage
• Magnetic disk
• Optical disk
• Magnetic tape
Keyboard
Computer mouse
Touch screen
Source data automation
Output Devices
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Printers
Video display terminals
Plotters
Audio output
Communications
Devices
Primary Storage
Central Processing Unit (CPU)
• Coordinating all computer operations.
• Performs arithmetic and logical operations on data.
• To process a program stored in main memory,
- CPU retrieves each instruction in sequence.
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Interprets the instruction to determine what should be
done.
- Retrieves any data needed to carry out that instruction
- Then CPU performs the actual manipulation.
• CPU’s current instruction and data values are stored
temporarily inside the CPU in special high-speed
memory locations called registers.
Central Processing Unit (CPU)
• The CPU consists of a control unit and an arithmeticlogic unit.
• Three kind of buses link the CPU, primary storage,
and other devices in the computer systems.
• The data bus moves data to and from primary storage.
• The address bus transmits signals for locating a given
address in primary storage.
• The control bus transmits signals specifying whether
to read or write data to or from a given primary storage
address, input device, or output device.
Data Bus, Address Bus, and Control Bus
Central Processing Unit (CPU)
Primary Storage
1
Arithmetic-Logic Unit
24 + 12 = 36
12 < 24
8
#
T
U
Control Unit
Data Bus
Address Bus
Control Bus
Input Devices
Output Devices
Secondary
Storage
Computer Software
• Software consists of the computer
programs that allow us to solve problems by
providing sets of instructions.
• Examples:
DOS, Windows, Mac. Office family, Lotus,
Netscape, Internet Explorer, Virus scans, tax
programs, computer games, GUI Graphical User Interface.
Computer Software
• Computer hardware is useless without software.
• Software is the set of instructions and associated
data that direct the computer to do a task.
• Software can be divided into two categories:
• system software and application software.
• System software helps the computer to carry out
its basic operating tasks.
• Application software helps the user carry out a
variety of tasks.
The major types of software
System Software
Application software
System software
Hardware
Operating Systems
Schedules computer events
Allocates computer resources
Monitor events
Language translators
Users
Application Software
Programming languages
Assembly language
FORTRAN, BASIC, PL/1
PASCAL, C
“4th generation “ languages
Interpreters
Compilers
Utility programs
Routine operations (e.g. sort,
list, print)
Manage data (e.g. create files,
merge files
System Software
• Manages the fundamental operations of the
computer, such as
• loading programs and data into memory, executing
programs, saving data to disks, displaying
information on the monitor, and transmitting data
through a port to a peripheral device.
• Four types of system software: operating systems,
utilities, device drivers, and programming
languages.
Operating System
• Collection of computer programs that control the
interaction of the user and the computer
hardware.
• Responsible for directing all computer operations
and managing all computer resources.
• Controls basic input and output, allocates system
resources, manages storage space, maintains
security, and detects equipment failure.
• A part of the operating system code is stored in a
ROM and the rest of it resides on a disk.
• Loading the operating system into memory is
called booting the computer.
Responsibilities of an Operating System
• Communicate with user, receive and execute commands,
show error messages.
• Manage allocation of memory, processor time and other
resources.
• Collect input from keyboard, mouse, and provide data to
running programs.
• Convey program output to screen, printer, or other output
device.
• Access data from secondary storage.
• Write data to secondary storage.
Application software
• Developed for a specific task , such as word
processing( MS Word/ WordPerfect),
accounting (Lotus 1-2-3/ Excel), or
database management (Access/ dBASE).
• Most applications are purchased on diskette
or CD-ROM.
• They are installed by copying the programs
from the diskettes/CD-ROM to the hard
disk.
Data Communications
• The transmission of text, numeric, voice, or video data
from one machine to another is called data
communications.
• For example, Send an electronic mail to your friends
around the globe.
• The four essential components of data communications
are a sender, a receiver, a channel, and a protocol.
Sender => The computer that originates the message is
called the sender.
Receiver => The computer at the message’s destination
is called the receiver.
Data Communications
Channel => The message needs some kind of medium
to be transmitted. This medium is called channel. For
example, telephone or coaxial cable, microwave signal,
or optical fibers
Protocol => The rules that establish an orderly transfer
of data between the sender and the receiver are called
protocols.
• Computer software and hardware establish these
protocols at the beginning of the transmission, and both
computers have to follow the protocols to ensure
accurate transfer of data.
Networks
• One of the most important types of data communications in
the business world is a network connection.
• A network connects one computer to another computers and
peripheral devices to share data and resources.
• There is a number of network configurations.
• local area network (LAN) => computers and peripheral
devices are located relatively close to each other, generally
in the same building.
• Client/server networks =>Some networks have file servers
(one or more computers) that act as the central storage
location for programs and that provide mass storage for
most of the data used on the network. A network with a file
server is called a client/server networks.
Networks
• Peer-to-peer networks => When a network does not
have a file server, all the computers essentially are
equal, and programs and data are distributed among
them. This is called a peer-to-peer network.
• Each computer that is part of the network must have a
network interface card installed. This device creates a
communication channel between the computer and the
network.
• Network software is also essential to establish the
communications protocols.
• Standalone computer => A microcomputer that is not
connected to a network is called a standalone computer.
Telecommunications
• Allows us to send and receive data over telephone
lines.
• A modem connects a computer to a telephone
jack.
• At the sending site, modem converts the digital
signal from a computer into analog (continuous
wave) signals (sound waves) that can traverse
ordinary phone lines (modulation).
• At the receiving site, a second modem converts
the analog signals back into digital signals
(demodulation).
Telecommunications
Internet
• The internet was originally developed for the government
to connect the researchers around the world to share data.
• Today, the internet is the largest network in the world that
connects millions of people in almost 200 countries.
• The use of internet:
electronic mail => This is the capability to send a message
from one user’s computer to another user’s computer
where it is stored until the receiver opens it. Message
passes through electronic links called gateways.
World Wide Web (Web) => Web is a huge database of
information that is stored on the network servers in places
that allow public access. The information is stored as text
files called web pages.
Internet
• Hyperlinks => a place on a computer screen that is
programmed to connect to a particular file on the same
network server, or on a network server on the other side
of the globe.
• Web browsing => communication software that help us
navigate the WWW is called web browsing software or
web browser.