Computer is an electronic device that accepts data as input, processes it, and provides results as output. It has three main components: the arithmetic logical unit (ALU) that performs calculations, the control unit (CU) that directs operations, and the central processing unit (CPU) that comprises the ALU and CU. Computers store data temporarily in RAM and permanently in various storage devices like hard disks, tapes, optical disks, and flash drives. They have evolved through five generations from vacuum tubes to today's integrated circuits and microprocessors. Computers come in various sizes ranging from supercomputers to desktops, laptops, and palmtop computers. They accept input through devices like keyboards and provide output through monitors and printers.

1. PGCET/ Computer basics
Intro

2. COMPUTER…
Computer is an electronic device which is capable of receiving
information or data and perform a series of operations in accordance
with a set of operations. This produces results in the form of data or
information.
It accepts and processes the data by doing some mathematical and
logical operations and gives us the desired output.

3. BASIC COMPUTER OPERATIONS
• Accepts data or instructions by way of input.
• Stores data,
• Processes data as required by the user,
• Gives results in the form of output, and
• Controls all operations inside a computer.

4. COMPUTER SYSTEM
• Arithmetic Logical Unit (ALU)
The processing of the data and instructions are performed by Arithmetic
Logical Unit. The major operations performed by the ALU are addition,
subtraction, multiplication, division, logic and comparison.
• Control Unit (CU)
The control unit determines the sequence in which computer programs and
instructions are to be executed. Activities like processing of programs stored
in the main memory, interpretation of the instructions and issuing of signals
for other units of the computer to execute them are carried out by CU.

5. • Central Processing Unit (CPU)
The ALU and the CU of a computer system are jointly known as the
central processing unit( CPU) system. It is just like brain that takes all
major decisions, makes all sorts of calculations and directs different
parts of the computer functions by activating and controlling the
operations. The CPU (Central Processing Unit) is the device that
interprets and executes instructions.

6. CHARACTERISTICS OF COMPUTER
• Speed
• Accuracy
• Versatility
• Diligence
• Power of Remembering
• Storage

7. GENERATION OF COMPUTERS
Generation, Period, Technology
First 1946-59 Based on vacuum tube technology
Second 1957-64 Transistor based technology replaces vacuum tube
Third 1965-70 Integrated circuit (IC) technology developed
Fourth 1970-90 Microprocessors developed
Fifth 1990-till date Use of Bio-Chip technology

8. TYPES OF COMPUTERS
Super Computer
Supercomputers are fastest computers and are very expensive. These
are employed for specialized applications that require immense
amounts of mathematical calculations. For example, weather
forecasting, animated graphics, fluid dynamic calculations, nuclear
energy research, and petroleum exploration.

9. Mainframe Computer
It is a very large and expensive computer and is capable of supporting
hundreds, or even thousands of users simultaneously. In the hierarchy
that starts with a simple microprocessor (in watches, for example) at
the bottom and moves to supercomputers at the top, mainframes are
just below supercomputers.
Mini Computer
It is a mid sized computer in size and power. It lies between
workstations and mainframes. In the past decade, the distinction
between large computers and small mainframes has blurred. In
general, a minicomputer is a multiprocessing system capable of
supporting from 4 to about 200 users simultaneously.

10. Micro Computer
1. Desktop Computer: a personal or micro-mini computer sufficient to
fit on a desk.
2. Laptop Computer: a portable computer complete with an
integrated screen and keyboard. It is generally smaller in size than a
desktop computer and larger than a notebook computer.
3. Palmtop Computer/Digital Diary /Notebook /PDAs (Personal Digital
Assistant): a hand-sized computer, Palmtop, does not have
keyboard, but its screen serves both as an input and output device.
4. Workstations: It is a terminal or desktop computer in a network. In
this context, workstation is just a generic term for a user’s machine
(client machine) in contrast to a “server” or “mainframe.”

11. INPUT AND OUTPUT UNIT
Input Unit
The data is entered / input into the computer through input devices.
The input devices translate the data / information from a natural
language in which the user is working, into the machine language
which the computer can understand. Computer language is in the form
of binary code (0 and 1).

12. Input devices are classified as follows:
• Human data entry devices - keyboard, mouse, joystick, trackball,
digitizing labels and; pick devices - light pen touch screens.
• Source data entry devices (Audio input –speech recognition; video
input -digital camera; scanners - optical scanner OCR, OMR, MICR,
Barcode Reader).

13. Output Unit
The output unit accepts output data from computer via output devices and
transforms the data into human readable form. All the information inside the
computer is in the form of binary digits (0 and 1). Output devices convert
them to numbers, words, graphics, sound and motion which we can easily
understand.
Output devices are classified as
● Hard copy device (Printer, Plotter, Computer Output on Micro-film)
● Soft copy devices (Monitor, Visual Display Terminal, Video Output and
Audio Response).

14. Memory
Memory is an internal storage area in a computer, which is
availed to store data and programs either permanently or
temporarily. Computer memory is broadly divided into two
groups and they are:
• Primary memory and
• Secondary memory
The Primary memory holds instructions and data when a
program is executing, the auxiliary memory or secondary
memory holds data and programs which are not currently in use
and furnishes long term storage.

15. • Primary memory:
• Primary memory is the only type of memory which is directly accessed by the CPU. The
CPU continuously reads instructions stored in the primary memory and executes them.
Any data that has to be operated by the CPU is also stored. The information is transferred
to various locations through the BUS. Primary memories are of two types. They are:
• RAM
• ROM
1.RAM: It stands for Random Access Memory. Here data can be stored temporarily, so this
type of memory is called as temporary memory or volatile memory because when power
fails the data from RAM will be erased. The information stored in the RAM is basically
loaded from the computer’s disk and includes information related to the operating system
and applications that are currently executed by the processor. RAM is considered random
access because any memory cell can be directly accessed if its address is known. RAM is
of distinct types like SRAM, DRAM, and VRAM.
2.ROM: It stands for Read Only Memory. In this, the data will be furnished by the
manufacturers regarding the system, so this information can simply be read by the user
but cannot add new data or it cannot be modified. ROMs are of distinct types:
• PROM – Programmable Read Only Memory
• EPROM – Erasable Programmable Read Only Memory
• EEPROM – Electrically Erasable Program

16. Secondary memory: Secondary memory or auxiliary memory consists of
slower and less expensive device that communicates indirectly with CPU via
main memory. The secondary memory stores the data and keeps it even
when the power fails. It is used to store or save large data or programs or
other information. The secondary storage devices are explained below:
1.Magnetic disks: Magnetic disks are made of rigid metals or synthetic
plastic material. The disk platter is coated on both the surfaces with
magnetic material and both the surfaces can be used for storage. The
magnetic disk furnishes direct access and is for both small and large
computer systems. The magnetic disk comes in two forms:
• Floppy disks
• Hard disks
2. Magnetic tape: magnetic tape is serial access storage medium and it can
store a large volume of data at low costs. The conventional magnetic tape is
in reels of up to 3600 feet made of Mylar plastic tape. The tape is one-half
inch in width and is coated with magnetic material on one side. The reel of
tape is loaded on a magnetic tape drive unit. During any read/write
operation, the tape is moved from one spool to another in the same way as
in the audiocassette tape recorder. The magnetic tape is densely packed
with magnetic spots in frames across its width.

17. 3. Optical drives: optical drives are a storage medium from which data is read and to which it is
written by lasers. Optical disks can store much more data up to 6GB. Optical store devices are the
most widely used and reliable storage devices. The most widely used type of optical storage devices
are explained below:
• CD – ROM
• DVD – ROM
• CD – RECORDABLE
• CD – REWRITABLE
• PHOTO – CD
4. USB flash drives: USB flash drives are removable, rewritable and are physically much smaller
drives, which have the weight of less than 30g. In the year of 2010, the storage capacity of the USB
flash drives was as large as 256GB. Such devices are a good substitute for floppy disks and CD –
ROMs as they are smaller, faster, have thousands of times more capacity, and are more durable and
reliable. Until 2005, most desktop and laptop computers had floppy disk drives, but nowadays floppy
disk drives have been abandoned in favor of USB ports. The USB connector is often protected inside
a removable cap, although it is not likely to be damaged if unprotected. USB flash drives draw power
from the computer through external USB connection. The most widely used USB flash drives are the
memory cards.
5. Mass storage devices: Mass storage devices refer to the saving of huge data in a persistent
manner. Mass storage machines can store up to several trillion bytes of data and hence are used to
store or save large databases, such as the information of customers of a big retail chain and library
transactions of students in a college. Some of the commonly used mass storage devices are
explained below:
• Disk array
• Automated tape
• CD – ROM jukebox

18. HARDWARE AND SOFTWARE
Hardware
Hardware refers to the physical equipment used for the input,
processing, output and storage activities of a computer system. It
consists of mechanical and electronic devices, which we are able to see
and touch easily. Some of them are central processing unit (CPU),
primary storage devices, secondary storage devices, input and output
unit and communication devices. These are explained below:-
● Central processing unit (CPU): It manipulates the data and controls
the tasks performed by the other components.
● Primary storage: It stores temporarily data and program instructions
during the processing.

19. ● Primary memory (main memory): These are RAM (Random Access
Memory/Read-Write Memory), and ROM (Read-only-memory).
● Secondary storage: These store data and programs for future use.
These are
Hard Disk (Local Disk) and External Hard Disc, Optical Disks,(CDR, CD-
RW, DVD-R, DVD-RW ), Pen Drive, Memory Cards, etc. Secondary
Storage Devices
Communication Devices: These are used for communication or flow of
data from
one computer to another computer. Some of them are Modem, Switch,
Router, TV
tuner card, etc.

20. Software
A computer cannot do anything on its own. It has to be guided by the
user. We have to give a sequence of instructions to the computer in
order to do any specific job.
Software is simply a computer program or a set of instructions.
Software guides the computer at every step indicating where to start
and stop during a particular job. The process of software development
is called programming.
There are two types of software,
• System software
• Application software.

21. System Software
System Software are general purpose programs designed to perform tasks such as
controlling all operations required to move data into and out of the computer. It
communicates with keyboard, printer, card reader, disk, tapes, etc. It also monitors
the use of various hardwares like memory, CPU, etc. System software acts as an
interface between hardware and application software. Remember that it is not
possible to run applicaion software without system software. Some of the system
softwares are Disc Operating System(DOS), Windows, Unix/Linux, MAC/OS X
Application software
It is a set of programs, which are written to perform specific tasks of the users of
computer. These softwares are developed in high level languages to help the user
to get the computer to perform various tasks. Some of the application software are
MS Office, Macromedia (Dreamweaver, Flash, Freehand), Adobe (PageMaker,
PhotoShop), LIBSYS, SOUL, WINISIS, KOHA, etc.

22. Internet
The Internet is a global system of interconnected computer
networks that use the standard Internet protocol suite (often
called TCP/IP, although not all applications use TCP) to serve
billions of users worldwide.

23. Terms to Be Familiar With:
• Browser- Contains the basic software you need in order to find, retrieve, view, and send
information over the Internet.
• Download --To copy data from a remote computer to a local computer.
• Upload —To send data from a local computer to a remote computer.
• E-mail - E-mail (electronic mail) is the exchange of computer-stored messages by
telecommunication. E-mail can bedistributed to lists of people as well as to individuals. However,
you can also send non-text files, such as graphic images andsound files, as attachments sent in
binary streams.
• Filter - Software that allows targeted sites to be blocked from view. Example: X-Stop, AOL@School
• Home Page - The beginning "page" of any site.
• HTML (HyperText Markup Language) - The coding language used to create documents for use
on the World Wide Web.There are three-letter suffixes used in coding that help to identify the type
location one is viewing
• HTTP (HyperText Transport Protocol) - the set of rules for exchanging files (text, graphic images,
sound, video, and othermultimedia files) on the World Wide Web. Relative to the TCP/IP suite of
protocols (which are the basis for informationexchange on the Internet), HTTP is an application
protocol.
• Hypertext - Generally any text that contains "links" to other text.
• Search Engine - A web server that collects data from other web servers and puts it into a database
(much like an index), it provides links to pages that contain the object of your search.

24. • TCP/IP -- TCP/IP (Transmission Control Protocol/Internet Protocol) is the
basic communication language or protocol of theInternet. It can also be used as a
communications protocol in a private network (either an intranet or an extranet).
When youare set up with direct access to the Internet, your computer is provided
with a copy of the TCP/IP program just as every othercomputer that you may
send messages to or get information from also has a copy of TCP/IP.
• URL (Uniform Resource Locator) - The Internet address. The prefix of a URL
indicates which area of the Internet will beaccessed. URLs look differently
depending on the Internet resource you are seeking.
• WWW (World Wide Web) - A technical definition of the World Wide Web is: all
the resources and users on the Internetthat are using the Hypertext Transfer
Protocol (HTTP).
What is a Web Browser?
A Web browser contains the basic software you need in order to find, retrieve,
view, and sendinformation over the Internet. This includes software that lets you
Send and receive electronic-mail (or e-mail) messages worldwide nearly
instantaneously. Read messages from newsgroups (or forums) about thousands of
topics in which users share information and opinions. Browse the World Wide Web
(or Web) where you can find a rich variety of text, graphics,
and interactive information.