Unit I
A computer is a machine that manipulates data according to a set of instructions.
Types of
Computers:
Based on operational principle, computers can be classified as
- Analog computers
- Digital computers and
- Hybrid computers
Analog Computers
Analog computers use continuous variables for mathematical operations.
They are mainly used to solve manufacturing, design and scientific problems.
These computers have to be constructed to perform only specific tasks.
Digital computers
The Digital computers work on the principle of binary digit system
such as “0” and “1”. They are useful for evaluating arithmetic expressions and
manipulation of data. The speed is very high when compared with analog
computers.
Hybrid computers
These types of computers are the combination of both Analog and
Digital computers. In the hybrid types of computers the digital segments
perform process control by conversion of analog signals to digital ones.
Based
on Capacity, speed and reliability computers can be divided into three categories.
They are
Mainframe Computer
These are computers used by large organizations like meteorological
surveys and statistical institutes for performing bulk mathematical
computations.
Microcomputer
These are the most frequently used computers known as “Personal
computers”. This is meant for public use. Other than Desktop Computer the
choice ranges as follows:
·
Personal Digital Computer
·
Tablet PC
·
Towers
·
Work Stations
·
Laptops
·
Hand Held Computer
Mini computer
Mini
computers like the mainframe computers are used by business organization. The
difference being that it can support the simultaneous working of up to 100
users and is usually maintained in business organizations for the maintenance
of accounts and finances. Minicomputers
lie in between mainframes and microcomputers.
A computer is an
electronic machine that accepts information, stores it until the information is
needed, processes the information according to the instructions provided by the
user, and finally returns the results to the user.
Functional Units of a Computer System
Digital computer systems
consist of three distinct units. These units are as follows:
Input unit
Central Processing unit and
Output unit
Input Unit
A computer must receive
both data and program statements to function properly and be able to solve
problems. The method of feeding data and programs to a computer is accomplished
by an input device.
Computer input devices
read data from a source, such as magnetic disks, and translate that data into
electronic impulses for transfer into the CPU. Some typical input devices are a
keyboard, a mouse, or a scanner.
Central Processing Unit
The brain of a computer system is the central processing unit
(CPU). The CPU processes data transferred to it
from one of the various input devices. It then transfers either an intermediate
or final result of the CPU to one or more output devices.
It consists of a control
section, an arithmetic-logic section, and an internal storage section (main
memory).
Control Section
The Control Unit (CU) is
the circuitry that controls the flow of information through the processor. It
also maintains order within the computer.
Arithmetic and Logic Section
The arithmetic-logic section
performs arithmetic operations,
such as addition, subtraction, multiplication, and division. Through internal logic capability, it tests various conditions encountered during processing and takes action based on the result.
Main Memory
Main memory holds instructions, programs and data for execution.
Memory is also known as primary memory and internal storage. The main memory of the computer is also known as RAM (Random
Access Memory).
This is the part of the computer that stores operating system
software, software applications and other information for the central
processing unit (CPU) to have fast and direct access when needed to perform
tasks.When power is lost, the information is lost.
Output Unit
It is a unit which delivers
information from the computer to an external device or from internal storage to
external storage. Output unit is anything that sends a signal out of the
computer.
A printer is a output unit and it is a peripheral
which produces a hard copy (permanent readable text and/or graphics) of
documents stored in electronic form, usually on physical print media such as
paper or transparencies.
Classification
of computers
Computers are classified according
to their data processing speed, amount of data that they can hold and price.
Depending upon their speed and memory size, computers are classified into
following four main groups.
- Supercomputer.
- Mainframe computer.
- Mini computer.
- Microcomputer.
Supercomputer
Supercomputer is the most powerful and fastest, and also very
expensive. It was developed in 1980s. It is used to process large amount of
data and to solve the complicated scientific problems. It can perform more than
one trillions calculations per second. It has large number of processors
connected parallel. So parallel processing is done in this computer. In a
single supercomputer thousands of users can be connected at the same time and
the supercomputer handles the work of each user separately. Supercomputer are
mainly used for:
- Weather forecasting.
- Nuclear energy research.
- Aircraft design.
- Automotive design.
- Online banking.
- To control industrial units.
Mainframe
Computers
These
are also very expensive. The mainframe computer specially requires a very large
clean room with air-conditioner. This makes it very expensive to buy and
operate. It can support a large number of various equipments. It also has
multiple processors. There are basically two types of terminals used with
mainframe systems. These are:
i) Dumb
Terminal
Dumb terminal does not have its own
CPU and storage devices. This type of terminal uses the CPU and storage devices
of mainframe system. Typically, a dumb terminal consists of monitor and a
keyboard (or mouse).
ii) Intelligent Terminal
Intelligent terminal has its own processor and can perform some
processing operations. Usually, this type of terminal does not have its own
storage. Typically, personal computers are used as intelligent terminals.
The
mainframe computers are specially used as servers on the World Wide Web. The
mainframe computers are used in large organizations such as Banks, Airlines and
Universities etc.
Minicomputers
These are smaller in
size, have lower processing speed and also have lower cost than mainframe.
These computers are known as minicomputers because of their small size as
compared to other computers at that time. The capabilities of a minicomputer
are between mainframe and personal computer. These computers are also known as
midrange computers.
The minicomputers are used in
business, education and many other government departments. Although some
minicomputers are designed for a single user but most are designed to handle
multiple terminals. Minicomputers are commonly used as servers in network environment.
Microcomputer
The microcomputers are
also known as personal computers or simply PCs. Microprocessor is used in this
type of computer. These are very small in size and cost. The IBM’s first
microcomputer was designed in 1981 and was named as IBM-PC. The most popular
types of personal computers are the PC and the Apple. Personal computers are
available in two models. These are:
- Desktop PCs
- Tower PCs
Microcomputers are further divided into
following categories.
- Laptop computer
- Workstation
- Network computer
- Handheld computer
1. Laptop computer
Laptop
computer is also known as notebook computer. It is small size (85-by-11 inch notebook computer
and can fit inside a briefcase. The laptop computer is operated on a special
battery and it does not have to be plugged in like desktop computer. The laptop
computer is portable and fully functional microcomputer.
The
memory and storage capacity of laptop computer is almost equivalent to the PC
or desktop computer. It also has the hard dist, floppy disk drive, Zip disk
drive, CD-ROM drive, CD-writer etc. it has built-in keyboard and built-in
trackball as pointing device.
2. Workstations
Workstations
are special single user computers having the same features as personal computer
but have the processing speed equivalent to minicomputer or mainframe computer.
A workstation computer can be fitted on a desktop. Scientists, engineers,
architects and graphic designers mostly use these computers.
Workstation
computers are expensive and powerful computers. These have advanced processors,
more RAM and storage capacity than personal computers. These are usually used
as single-user applications but these are used as servers on computer network
and web servers as well.
3. Network
computers
Network
computers are also version of personal computers having less processing power,
memory and storage. These are specially designed as terminals for network
environment. Some types of network computers have no storage.The network
computers are designed for network, Internet or Intranet for data entry or to
access data on the network.
4. Handheld computer
These
computers are also referred to as Palmtop Computers. Because of its reduced
size, the screen of handheld computer is quite small. Similarly it also has
small keyboard. Some handheld computers have a specialized keyboard. The
examples of handheld computers are:
¨
Personal Digital Assistance
¨
Cellular telephones
¨
H/PC Pro devices
Personal Digital Assistance - A PDA provides special functions such as taking notes, organizing
telephone numbers and addresses. Most PDAs also offer a variety of other
application software such as word processing, spreadsheet and games etc.
Some
PDAs include electronic books that enable users to read a book on the PDA’s
screen. Many PDAs are web-based and users can send/receive e-mails and access
the Internet.
The
primary input device of a PDA is the stylus. A stylus is an electronic pen and
looks like a small ballpoint pen. This input device is used to write notes and
store in the PDA by touching the screen. Some PDAs also support voice input.
Cellular telephones - A cellular phone is a web-based telephone having features of
analog and digital devices. It is also referred to as Smart Phone. A cellular
phone also provides the functions to receive and send e-mails & faxes and
to access the Internet.
H/PC Pro devices - These devices have features between PDAs and notebook PCs. The H/PC
Pro device includes a full-size keyboard but it does not include disk. These
systems also have RAM with very low storage capacity and slow speed of
processor.
Computer software
¨
A set of instruction given to the
computer to solve user problems and to
control different operations of computer is known as computer software.
¨
A set of programs and instructions are
written by the user is called software.
¨
For eg:
tally, ms-office, oracle, java,
vb etc.
¨
A software package is a group of
programs which solve a specific problem or perform a specific type of job.
¨
For eg: word processing package may
contain programs for text editing, text formatting, drawing graphics, spelling
checking etc.
Software can be divided
into two major categories.
¨
Application software
¨
System software
Application
software:
¨ A set
of program used to solve a particular problem of user through computer is
called application software.
¨ It is
also known as application package.
¨ The
ready packages are also available in market on CDs for various purpose.
¨ The
user solve their problem by using ready packages more easily and quickly.
Some of the application packages are:
¨ Word
processing software
¨ Database
management system software
¨ Graphics
software
¨ Entertainment
software
Word processing software:
This software is
used to create and edit document such as letter, essays etc. word processing software provides several features for
document editing and formatting.
Eg: Microsoft word
Database management system software:
This software is
used to create and manage database . A
database is a collection of related information or records. DBMS is stores and
manage records in database.
Eg: Microsoft
access and oracle is an eg of DBMS.
Graphics software:
It is used to
create slides for making presentation .
Eg: power
point presentation.
Entertainment software:
It allows a
computer system to be used as an entertainment tools.
Eg: video games
is an eg for entertainment software.
System software:
¨ System
software is a set of programs that controls the operations of computer and
devices attached with the computer.
¨ It
creates link between user and computer as well as controls the execution of
application program.
¨ Without
these software no link can be created with user and computer.
The examples of system software are:
¨ Operating
system software
¨ Communication
software
Operating system software:
Every computer
has an operating system software which takes care of the effective
and efficient utilization of all hardware and software components of the
computer system.
Communication software:
In a network
environment communication software
enables transfer of data from one computer system to another.
Input device
An input device is used to transfer
information into the computer. Computer input devices
are accessories that control how a computer processes information. A computer
input device sends data to the computer.
An input device is any
peripheral used to provide data and control signals to an information
processing system (such as a computer). The first input
devices were punch cards and later keyboards.
Input devices are the accessories
that give the computer's central processing unit (CPU) data with which to work.
The CPU processes the information and then displays results to the user.
Keyboard
The keyboard is the primary device for inputting
information to a computer. It operates by converting key presses to electronic
signals in binary digital form. The typical computer keyboard has the standard
character keys found on a typewriter together with a number of special keys.
·
Function keys which can be
programmed by the user or by the software being run, so that a single key
depression sends a command or string of commands to the computer.
·
The CTRL and ALT keys (short
for Control and Alternate), which are always used in conjunction with other
keys to issue commands to the computer.
·
The Backspace key, which delete
the character to the immediate left of the cursor on the screen.
·
The four arrow keys, which move
the cursor one character position in the direction of the arrow.
·
The PageUp and PageDown keys,
which are normally programmed to move the cursor one page up or down.
·
The Home key, which may be
programmed to move the cursor to the left of the screen or the beginning of the
document.
·
The End key, which may be
programmed to move the cursor to the right of the screen or the end of the
document.
·
The Esc key, which is often
programmed to enable the user to escape from the currently selected option.
Mouse
The mouse is the most common
pointing device and contains one or more buttons with which a user can interact
with an application.
With the introduction of graphic
user interfaces (GUIs), the mouse acts as an input device. Mice allow the user
to control an on-screen pointer, called a cursor, which commonly looks like an
arrow. When the arrow is properly positioned, the user can use it to perform
various tasks by pressing buttons on the mouse
Move
Press
Pressing and holding down
a mouse button. A press can initiate an action, such as dragging an object to a
printer icon.
Press and
move
Pressing a mouse button
without releasing it and then moving the position of the pointer, such as
moving an element (like an icon) across the screen.
Release
Releasing a mouse button
after pressing it. Releasing the mouse button performs an action initiated by
pressing it, such as activating a push button.
Click
Pressing and releasing a
mouse button without moving the pointer. Clicking a mouse button can perform an
action such as activating a menu item.
Double-click
A double-click performs
the default action of a control. The time interval between clicks can be user
defined.
Multi-click
Double-press
Multi-press
Performing a number of
clicks followed by a press in quick succession without moving the pointer
Joysticks
Joysticks
are most commonly used when playing games. Originally, they consisted of a
single movable stick and a button or two, allowing the user to control a game
character's movements. Modern joysticks group a number of sticks and buttons
together, allowing the user to control complex movements with a couple of
finger flicks.
Touch screens
Touch screens
Touch screens are used by touching
the display area with either a finger or stylus. It enables one to interact directly with what is
displayed, rather than indirectly with a cursor controlled by a mouse or touchpad.
Also,it lets one to do operations without requiring any intermediate device
that would need to be held in the hand. They can be
found on PDAs, mobile phones,
video games and tablet PCs.
Uses
¨
Dusty, dirty or wet environments
where a keyboard would be damaged e.g) Factory floors
¨
Hazardous environments where
there may be any chance of a spark e.g) Chemical plants
¨
Constricted areas where there
is no room for another input device e.g) Satellite Navigation system on a car
dashboard
¨
Hygienic environments where it
must be simple to wipe clean e.g) urgical theatres
Touch pad
A
touch pad (also trackpad) is a
device for pointing (controlling input positioning) on a computer display
screen. It is an alternative to the mouse. It consists of specialized surface
that can translate the motion and position of a user's fingers to a relative
position on screen.Originally incorporated in laptop computers, touch pads are
also being made for use with desktop computers. A touch pad works by sensing
the user's finger movement and downward pressure.
The first touch pad was
invented by George E. Gerpheide in 1988. Apple Computer was the first to
license and use the touch pad in its Powerbook laptops in 1994.
Magnetic Ink
Character Recognition
The acronym MICR stands for Magnetic
Ink Character Recognition. This technology uses magnetically chargeable
ink or toner to print the numbers and special characters on the bottom of
checks or other financial transaction documents. The technology allows computers to read
information (such as account numbers) of printed documents.
It is a technique that enables
special characters printed in magnetic ink to be read and input rapidly to a
computer. MICR is used extensively in banking because magnetic-ink characters
can be machine-read with much greater accuracy than human reading or other optical
character recognition (OCR) systems, and are therefore ideal for marking
and identifying the account and sort code numbers on cheques.
Optical Mark Reader
OMR
A
special scanning device that can read carefully placed pencil marks on
specially designed documents. OMR is frequently used in forms, questionnaires,
answer-sheets.
The
Optical Mark Reader will be referred to as the scanner or OMR. The computer
test forms designed for the OMR are known as NCS compatible scan forms. Tests
and surveys completed on these forms are read in by the scanner, checked, and
the results are saved to a file. This data file can be converted into an output
file of several different formats.
Advantages
¨
Good for inputting large volume
of data at low cost.
¨
Very little training or
instruction required to use.
¨
Good for multi-choice
questionnaires
¨
A quick and reliable way of
inputting large volume of simple data
Disadvantages
¨
Can only input a limited data
set
¨
Poorly marked forms/cards cause
errors.
¨
Creased/folded forms cause
errors
¨
It can't be used for bulk
text/numbers input.
Barcode reader
A barcode reader
(or barcode scanner) also called a price scanner
or point-of-sale ( POS ) scanneris an electronic device for reading printed barcodes. A barcode reader consists of a scanner, a decoder and a cable used
to connect the reader with a computer. Because a barcode reader merely captures
and translates the barcode into numbers and/or letters, the data must be sent
to a computer so that a software application can make sense of the data.
A barcode reader works by directing
a beam of light across the bar code and measuring the amount of light that is
reflected back. The scanner converts the light energy into electrical energy,
which is then converted into data by the decoder and forwarded to a computer.
Scanner
Scanners are devices that receive
images from documents like images or paper. The scanner runs over the colours
and writing on the paper, and the device sends it to the computer. Users
normally have custom software that is included with the scanner. This software
displays the images that were taking from the scanner's surface.
Scanners work much like photocopiers. A digital image of the document is
created that can be saved in the computer's memory, then printed or saved. This
is an image, and must be edited in a graphics program. To convert this image to
text for manipulation in a word processor, OCR (optical character recognition)
software is needed
to make the
conversion.
Cameras
Cameras are also a computer input
device.
Two types of cameras are used for input
on a computer. The digital camera is a device that takes digital images and
saves them to memory. The user then connects the camera to the computer where
images are uploaded and saved. Web cams are the other type of camera that
connects to the computer. Web cams are ways for people to take images from the
computer and communicate visually with other users on the Internet.
Any peripheral that receives and/or
displays output from a computer. An output device is any piece of computer
hardware equipment used to communicate the results of data processing carried
out by an information processing system (such as a computer) to the outside
world.
Monitor
A monitor or display
(sometimes called a visual display unit) is an electronic visual display
for computers. The visual display of the processed data, which the users can
view is got through the monitor.
Computer monitors come in
a variety of screen sizes with different visual resolutions. There are two
types of computer monitors available, namely CRT and flat panel. All monitors
rely in a video card, which is located on the motherboard to display the
information. It is the video card, which processes the data into images, which
is eventually displayed on the monitor.
The display device in
modern monitors is typically a thin film transistor liquid crystal display
(TFT-LCD) thin panel, while older monitors use a cathode ray tube (CRT).
Printer
A
printer is an output device that produces text and graphics on paper.
The speed of a printer is measured in:
|
cps
|
= characters per second
|
|
lpm
|
= lines per minute
|
|
ppm
|
= pages per minute
|
Printers can be divided into two
main groups, impact printer and non-impact printer. Impact
printer produces text and images when tiny wire pins on print head strike the
ink ribbon by physically contacting the paper. Non-impact printer
produces text and graphics on paper without actually striking the paper.
Printers can also be categorized
based on the print method or print technology. The most popular ones are inkjet
printer, laser printer, dot-matrix printer and thermal
printer. Among these, only dot-matrix printer is impact printer and
the others are non-impact printers
Line
printer
The line printer is a form of
high speed impact printer. A line printer uses a long
drum imprinted with raised characters. As the drum rotates, words are formed on
the page. The drum moves in a horizontal direction, printing one line at a
time. Line printers have limited font availability and no graphic capability.
Advantages
Advantages
¨ They are less expensive
¨ They can print large, custom-sized pages
and produce carbon copies, and
¨ Easier to maintain
¨ Because of the nature of the print mechanism, line printers are much faster than dot-matrix or daisy-wheel printers;
Disadvantages
¨ They tend to be quite loud,
¨ Have limited multi-font capability, and
¨ Often produce lower print quality than more recent printing technologies.
serial
printer It is a printer
that prints a single character at a time. It is attached with the computer
through a serial interface.
Dot
Matrix printers
Dot-matrix printer is an
impact printer that produces text and graphics when tiny wire pins on the print
head strike the ink ribbon. The print head runs back and forth on the
paper like a typewriter. When the ink ribbon presses on the paper, it
creates dots that form text and images. Higher number of pins means that
the printer prints more dots per character, thus resulting in higher print
quality.
Advantages of
dot matrix printer:
1) Can print on multi-part
forms or carbon copies
2) Low printing cost per
page
3) Can be used on continuous form paper, useful for data logging
4) Reliable, durable
Disadvantages of dot matrix
printer:
1) Noisy
2) Limited print quality
3) Low printing speed
4) Limited color printing
Inkjet printers
Inkjet printers are non-impact printers
which print text and images by spraying tiny droplets of liquid ink onto
paper. The ink is
stored in disposable ink cartridges. often a separate cartridge is used
for each of the major colors. These colors are usually Black, Red/Magenta,
Green/Cyan, and Yellow (CYMK).
They are the
most popular printers for home use. Ink-jet printers are capable of producing
high quality print which almost matches the quality of a laser printer. A
standard ink-jet printer has a resolution of 300 dots per inch.
Advantages of inkjet printers:
¨
Low cost
¨
High quality of output, capable
of printing fine and smooth details
¨
Capable of printing in vivid
color, good for printing pictures
¨
Easy to use
¨
Reasonably fast
¨
Quieter than dot matrix printer
¨
No warm up time
Disadvantages of inkjet printers:
¨
Print head is less durable,
prone to clogging and damage
¨
Expensive replacement ink
cartridges
¨
Not good for high volume
printing
¨
Printing speed is not as fast
as laser printers
¨
Ink bleeding, ink carried
sideways causing blurred effects on some papers
¨
Aqueous ink is sensitive to
water, even a small drop of water can cause blurring
¨
Cannot use highlighter marker
on inkjet printouts
Thermal printers
Thermal printers use two types of printing
technologies: direct thermal and thermal transfer printing.
Thermal
printers worked by pushing electrically heated pins against heat-sensitive
paper (thermal paper). The coating on the thermal paper turns black in
the areas where it is heated, producing characters or images.
Thermal printers are often used in cash
registers, ATM and point-of-sales terminals.
Advantages
¨
Direct thermal printers have no
ink, toner or ribbon.
¨
These printers are durable,
¨
Easy to use and
¨
Cost less to print than other
printers.
Disadvantages
¨
The thermal paper is sensitive
to heat, light, water, and abrasion and
¨
The text and images may fade
over time.
In
thermal transfer printing, a thermal print head applies heat to a
heat-sensitive ribbon, which melts ink onto paper and a wide range of materials
to form text and images. The printouts can be extremely durable and can be
stored over long period of time.
Programming Language
A language is a means of communication. Similarly a programming language
is used by a programmer to instruct a computer what he/she wants it to do.
A language that is acceptable to the computer system is called a
computer language or computer programming language, and the process of writing
instructions in such a language for an already planned program is called
programming or coding. All computer languages can be broadly classified into
the following three categories:
¨
Machine language
¨
Assembly language
¨
High-level language
Machine
Language:
Although computers can be programmed to understand many different
computer languages, there is only one language understood by the computer
without using a translation program. This program is called the machine
language of the computer. The machine language of a computer is normally
written as string of binary 1s and 0s. The circuitry of the computer is wired
in a manner that it immediately recognizes the machine languages instructions,
and converts them into the electrical signals needed to execute them.
A
machine language instruction normally has two-part format.
|
OPCODE
(operation code)
|
OPERAND
(Address/Location)
|
The first part of an instruction is the
operation code, which tells the computer what function to perform, and the
second part is the operand, which tells the computer where to find or store the
data or other instructions, which are to be manipulated. Hence each instruction
tells the computer what operation to perform, and the length and locations of
the data fields, which are involved in the operation. Typical operations
included in the instruction set of a computer are:
¨
Arithmetic operations
¨
Logical operations
¨
Branch operations
¨
Data movement operations for moving data between memory locations and
register
¨
Data movement operations for moving data from or to one of computer's
input/output device
Advantage:
¨
Programs can be executed very fast by the computer.
¨
No translation of the program is required.
Disadvantages:
¨
Machine dependent: Because the internal design of
every type of computer is different from every other type of computer, the
machine language also differs from computer to computer.
¨
Difficult to program. It is necessary for the
programmer either to memorize the dozens of operation code numbers for the
commands in the machine’s instruction set or to constantly refer to a reference
card. A programmer is also force to keep track of the storage location of data
and instructions. Moreover a machine language programmer must be an expert who
knows about the hardware structure of the computer.
¨
Error prone. A programmer has to remember the
opcodes, and must keep track of the storage locations of data and instructions
it becomes very difficult for him /her to contribute fully on the logic of the
program. This frequently results in programming error.
¨
Difficult to modify. It is difficult to correct or
modify machine language programs. Checking machine instructions to locate
errors is very difficult and time consuming.
In short, writing a program in machine
language is so difficult and time consuming that it is rarely used today.
Assembly Language
A language, which allows instructions and storage locations to be
represented by letters and symbols, instead of numbers is called an assembly
language or symbolic language. A program written in an assembly language is
called an assembly language program or a symbolic program. Assembly language
programming which was introduced in 1952 helped in overcoming some of the
limitations of machine language programming in the following manner:
1.
By using alphanumeric mnemonic codes, instead of numeric codes for the
instruction in instruction set. For e.g. using ADD instead of 1110(Binary)or
14(decimal)for the instruction to add.
2.
By allowing storage location to be represented in the form of alphanumeric
addresses instead of numeric addresses. For e.g. the memory locations 1000,
1001, 1002 may be represented as FRST, SCND and ANSR respectively.
3. By providing additional instructions called
pseudo-instructions in the instruction set which are used for instructing the
system how we want the program to be assembled inside the computer memory.
Assembler:
A
computer can directly execute only machine language programs so assembly
language program must be converted (translated) into its equivalent machine
language programs before it can be executed on the computer. This translation
is done with the help of a translated program, which is known as an assembler.
|
Assembly language program
machine language program
Advantages:
Ø Easier to understand and use. Due to the use of mnemonics, instead of
numeric op-codes, and symbolic names for data locations, instead of numeric
addresses, assembly language programs are much easier to understand than
machine language programs.
Ø Easier to locate and correct errors. Programmer need not keep track of the
storage locations of the data and instructions. So it is easy to write program
in assembly language. Assemblers are designed to automatically detect and
indicate errors for use of an invalid mnemonic op-code or a name that has never
been defined.
Ø Easier to modify. Since it is easier to understand it is easier to locate, correct, and
modify instructions of an assembly language program than a machine language
program.
Ø No worry about addresses. Programmer need not keep track of the
storage locations of the data and instructions while writing assembly language
program.
Ø Easily relocatable.The availability of pseudo-instructions for instructing the system how we
want the program to be assembled inside the computer memory makes assembly
language program easily relocatable, because their location can be easily
changed by suitably changing the pseudo instructions.
Ø Efficiency of machine language. An assembly language program is one-to-one
correspondence between the instructions of an assembly language program and its
corresponding machine language program. Hence leaving out the transaction time
required by the assembler, the actual execution time for an assembly language
program, and its equivalent machine language program will be the same.
Disadvantages:
Ø Machine dependent. Assembly languages differ from computer to computer and an assembly
language can executed only on the computer in whose assembly language it has
been written.
Ø Knowledge of hardware required. Since assembly languages are machine
dependent an assembly language programmer must have a good knowledge of the
characteristics, and the logical structure of his /her computer to write good
assembly language programs.
Ø Machine level coding. In case of an assembly language, instructions are still written at the
machine code level. That is one assembly language instructions are substituted
for one machine language instruction. Hence writing assembly language programs
is still time consuming and not very easy.
Uses of
computers in Education
Computers are used successfully not
only in the classroom of schools and colleges but also in the offices.
Administrative
uses
Many educational institutions
computerize nearly all their operations from mailing labels to staff payroll.
Computerizations of administrative functions are:
1. Office
Applications
In the offices, computers are used
in filing, typing/word processing, preparing mailing for dispatch and making
labels of addresses.
2. Library
Applications
In the library, computers are used
for retrieval of bibliographic information, cataloguing, circulation,
purchasing of books, journals etc., searching books and charging fines from
students. Also databases can be prepared of the different users of library.
3. Financial
Applications
Computers are used for making
budgets, auditing, accounts receivable/payable, general ledger, purchase order
generation, salary schedule analysis and maintenance of student’s fees records
etc.
4. Student
Applications
Computers are used to make time
table for students, report cards, grade information, maintenance of attendance,
students’ health and demographic records, result processing, fees statements,
railway concessions cards, bio-data of students etc.
5. Personnel
Applications
Computers are used to prepare
payrolls of workers, maintenance of personnel records staff assignments, leave
records of teachers, health records, tax information and reporting, issuing
circular to teaching and non teaching staff, maintaining bio data of teachers
and non teaching staff.
6. Research
and Planning Applications
Computers
are used in various research and planning applications such as bus routing,
test item analysis, project planning and evaluation, budget forecasting,
feasibility of opening new courses etc. In well equipped modern educational
institutions like IGNOU most of these functions are performed through
computers.
Academic
Uses- Instructional Uses
Before the advent of micro
computers, in 1960’s and 1970’s, when
computer uses were limited, instructional uses were generally classified as CAI
(Computer Aided Instruction) or CMI(Computer Managed Instruction). In CAI
students received some kind of direct instruction via a computer screen. Drill
and practice, tutorial and simulation programs fall under this category.
Now-a-days multimedia presentations, CBT’s(Computer Based Training), Internet
are widely used in the field of education.
CAI (Computer
Aided/Assisted Instruction)
CAI consists of text material, test
questions requiring students’ responses, additional backup instructional
material and analysis of programmes. Student’s at CAI terminals can proceed
through lessons at their own rate. Each terminal can evaluate specific lessons,
independently of the others.
In CAI, if
students cannot understand the main text, they are given access to alternative
explanations. The students are provided with immediate feedback. It requires
less student time.
¨
Computer Assisted Instruction
is nothing but giving instructions with the help of computers.
¨
In CAI, the activity of the
learner is the most important attribute.
¨
CAI is nothing but learning
with computers.
¨
It can be used to impart formal
and non-formal education at all levels and also in all areas
¨
CAI has been developed from the
principles of Programmed Instruction
¨
It is one of the types of
Individualized Instruction
¨
CAI
uses a combination of text, graphics, sound and video in enhancing the learning
process
CMI (Computer
Managed Instruction)
Computer-managed instruction is an instructional strategy whereby
the computer is used to provide learning objectives, learning resources, and
assessment of learner performance. It refers to the use of a computer system to
manage information about learner performance and learning resources options in
order to prescribe and control individual lessons.
Computer-managed
instruction (CMI) aids the instructor in instructional management without
actually doing the teaching. Central CMI
themes discussed in the literature are individualization, behavioral objectives,
and educational technology.
Computer in Teaching Learning process
In computer managed instructions, the computer gathers, stores and
manages information to guide students through individualized learning
experience.
As the computer is being used in
administrative and management, these days, such type of use of a computer is
known as computer based learning, for example in distributing the salaries of
the teachers and other employers.
Computer is not used directly in
teaching – learning process, but it used as an helper in teaching learning
process. If a teacher is made free by assigning his other duties to the
computer such as administrative, managemental activities, then he can utilize
his spare time in an effective manner in the classroom.
Computer Managed
Testing
Computers are used in the
preparation, administration and scoring of tests. Various items of the tests
are collected and pooled. These item pools are stored as computer files. With
the help of computers items pools are managed and updated. Whenever needed,
they can be retrieved. Computers are used for preparing tests.
Tests can be conveniently
administered by a computer. During the testing sequence a decision algorithm is
used repeatedly which decides the sequence of questions to be asked and the
point at which to stop the test.
Computers are used to process test
data. Numerous scores can be computed. Consequently detailed and individualized
feedback may be provided. Teachers can also get individual results detailing
e.g, which student’s have mastered which objectives.
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