5)On the basis of brand
On the basis of brand computer can be classified as:

i) IBM
The computer that are manufactured by IBM are known as IBM PC.IBM PC is one of the leading company of the world in manufacyuring computers.These are more reliable ,durable & have better quality.It was also very expensive in comparision to IBM compatible computer.It was specifically designed for professional & scientific problem solves.

ii) IBM Compatible
The computers that are manufactured by other companies but having same technology & fetures of IBM PC are known as IBM Compatible.such computers are refer to as Pc clones or IBM clones.Since they almost exactly duplicated all significant features of PC architecture facilated by various manufactures.

iii)Apple Mac
the computers that are manufactured by Apple Mac company but having different architecture & configuration then IBM compatibles are known as Apple Mac.They have system produced by Apple company for their maintosh is called Mac OS.




) 6) On the basis of model

i) XT(Extra Technology)
The computers having 8000 ,8086 ,8088 microprocessor & processing speed of 4.TT mega hertz are known as XT.It can’t support GUI (Graphics User Interfare) based operating system.

ii) AT
The computer having 80286 ,80386 ,80486 ,Pentium-I Pentium-II & Pentium-IV microprocessor & processing speed.

iii) PC 12
It is a laptop computer with rechargeable battery based system.It is operated with OC1R operating system.These computers are use refinal architecture making the computer faster than AT computer.They can almost all programe.eg:laptop hand held computer.

Number system.

1. Decimal (0-9)10
2. Binary (0-1)2
3. Octal (0-7)8
4. Hex (0- )

Today we can’t imagine a world without numbers.It took thousands of years to get the decimal number system.In the stone age man used pebbles sticks & different types of symbols for counting numbers.all the techniques requires some physical power from man.The process was very slow & a lot of works was required for large calculation.Later on above techniques were replaced by the present day number system.Besides decimal number system there are other system namely binary ,octel & hex.

1 ) Decimal number system
The number system having base10 is called decimal number system.it includes 10 digits.Since there are 10 digits in decimal number system it’s base is 10.The order of base values in decimal number system are 1 ,10 ,100 ,1000 e.t.c.

2) Binary number system
The number system having base 2 is called binary number system.It includes only two digits 0 & 1.Since there are omly two digits it’s base value is two.The order of two values in binary number system are 1 ,2 ,4 ,8 ,16 ,32 ,84 ,128 , & so on.
1 or 0 is also called bit ,which represents two logic conditions:
1.True &
2.False

1) Octal number system
The number system having bsae 8 is called octal number system.it includes 8 digits i.e. 0-7.Since there are 8 digits in octal number system it’s base is 8.

5)Hexa decimal number system
The number systemj having base 16 is called hexa decimal number system.It includes 16 digits.eg: (0-9 A ,B ,C ,D ,E ,F).Since there are 16 digits it’s base is 16.

Fourth generation of computer
The fourth generation of computer were developed during 1974-till.They used micro chips having about -50,000 transistors on a chip as a major component.
A micro chip is a single chip that consists of the entire computer circuiting American intel corporation develop the first microprocessor called 4004 in 1971.The main features of this generation of computer are:
-Highly reduce the size of computer.
-The operating speed increase beyond HIPS(million Instruction Per second)
-Magnetic & optical storage devices with capacity more than 360 GB.
-Mltiprocessing & multiprogramming operating system are used.
-4G(Fourth generation) languages are used eg:Ctt,Java,Net e.t.c.
-Eg:8086,8088,80286,80386,80486,80586,(Pentium-I,II,III,IV) e.t.c.

Fifth generation of computer
The development of fifth generation of computer is being started but not completed til now.These computer will use Bio chips which are made from Gallium & Arsenite as major component.Japan has been working to develop such computer using the concept of A.I.
(Artificial Intelligence)
Features of fifth generation of computer
-Able to understand human language & speak ,think & make decision.
-Can perform large number of parallel processing.
-Speed is extremely high.


Classification of computer
1) On the basis of work.
a. Analog computer
It work on the supply of continious electrical pulse.The display of output is also continious.It has a very limited memory.It can perform a limited type of calculation.It is used for only scientific research & engineering purpose.eg:automobile ,speedometer ,clock with a two hand & slide rule.

b. Digital computer
It dosen’t work on the supply of continious electrical pulses.It has a very big memory.Generally ,we use digital computer in our daily lifea.It is used not only for scientific research & engeneering purpose but also in industries ,government sector ,education ,medicine ,law ,social services e.t.c. a digital computer is one that directly counts numbers or digits that presents numbers ,letters or other special symbols.eg:digital clock ,present computer.


c. Hybrid computer
The computer that processes the features of both analog as well as digital is called hybrid computer.These are used on intensive care unit of hospitals ,jet planes & other data analysis terminals.It is very useful & confidend in scientific research ,medicine & engineering purposes.


#Difference between Analog & Digital computer
1) Analog computer
#It is costly.
#It is used in scientficial ,medical & industrial field.
#It is specific slow & less accurate.

2) Digital computer
# It is less costly.
# It is used for statical data numerical problem &
Science
#It is versatile ,fast & accurate.


1) On the basis of size
a. Super
It is the largest computer of very high efficiency & storing capacity having feature of multi user of multi processer.It be able to solve very difficult & complex problems within a nanosecond.It use RISC processor.(Reduced Instructor Set Computer)
It is used in the following:
1) Used in forecasting weather & climate.
2) Used in millitary research & defense system.
3) Used in encrypting decoding sensitive intelligence information.
4) Used in automobile aircraft & spacecraftdesigning.
5) Used in seismography plasma & nuclear research.
6) Study of DNA structure & gene engeneering.
7) Digital film rendering.
8) In metrology
Eg:PAEAM ,services developed by C-DAC ANURAG ,CRAY-I ,CYBER 205 e.t.c.


b. Mainframe computer
It is very powerful muti-user ,general purpose computer system & supports wide range of input & ontput terminals with large backing storage capacity.It supports large number of terminals upto 100 or more.It works on the hime saving basis.the first mainframe compater dereloped by ibm was system 360.

Applications:
-Credit card procession.
-Bank account management.
-Business data processing.
-Air traffie coutem & induslrial design.
Eg:system1360 ,IBM 51390 ,IBM 51709 e.t.c.

3) Mini computer
Mini computer is also known as mid-range comouters & more powerful & larger than micro computer.It is also multiuse computer & supports more then dozens of people at a time.
Applications:
-Used in universities.
-Used in large business.
-Used in scientific research instrumentation
System ,industial process.
-Used in monitering & controlling system eg PDP-II (Program Data Processor)

2) Micro computer
It is also called home PC or desktop PC because it is a single user computer.it supports many high level languages ,multimedia graphics ,3D-graphics & games.It is popular among students ,professionals due to small size ,low price & low maintainance cost.

Application:
- For different programming ,graphic designing &
desktop publishing.
- For listening multimedia songs e.t.c.

Types of micro computer
i)Laptop
ii)Palmtop
Types of micro computer
i) Laptop
ii) Palmtop
iii) Multimedia
iv) PDA (Personal Digital Assistant)



i) Laptop/Palmtop
These are small ,portable ,less power consuming & equipped with all the facilities of modern PC.These computers can be operated by battery.These computers have as equal as storing capacity like desktop & all facilities are included.It has CD-Drive ,FLOPPY DRIVE ,COMBO & other input output parts.

The idea of laptop computers was started by Alien kay of Xerox palo alto research centre in 1970 & named to notebook but the first laptop was designed by William Moggrage of grid system in 1979.Palmtop computers are very useful for remote areas where there is no electricity. Facility available.
The higher authorities ,social working in remote areas.They get more benefit by palmtop as well as laptop.
Simply the desktop is your personal computer seated at the top of your disk laptop as no problem on your lap & palmtop on your palm.


ii)Multimedia computer
Multimedia is a combined form of two or more media like as text ,graphic ,sound & animation e.t.c. ADC (Analog Digital Computer) converts he sound wave into digital signal in multimedia computer MPEG (Motion Picture Expert Group) is a standered use to compress sound (audio) & videos for computer name HPEG-1 ,MPEG-2 e.t.c.


iii) PDA
PDA is a small sized portable hand-held electronic edvice which has all the features of PCs.It has input processing storage & output capability like the other micro computer.We can transfer data from PDA to PC & PC to PDA.It is used for daires calendar ,address ,book e.t.c.

(3)UAIUA
It stands for Universal Automatic Computer developed by J.P eckret & DR. John Mouchly in 1961.It was capable of processing alpha numeric data & based on the concept of stored memory of John newman.It was used for business data processing which was the first computer manufactured for commercial use & general purpose digital computer.

(4)EDSA
It stands for Electronic Delay Storage Automatic Computer.altough the concept of store programme was introduced EDVAC,EDSAC was the first computer implementing this concept.It was designed by Mauric Willes in 1947.It is used as Mercury delay line storage system where the exess time was 1 mini second.It contains 3,000 vacum tubes & operated on 30 kilo watt.

History of computer in Nepal:
-First ‘Facit’ named calculating device was brought in
2018 B.S. for census purpose.


-In 2028B.S. “IBM 1401” was the first computer computer brought in Nepal which was the second generation of computer.

-During 2039 B.S. different types of computer like ‘Sirus’ ,‘Apple Mac’ e.t.c. was brought.

-Till now we are using laptops,palmtops e.t.c. & the technology is still using.

#Generation of computer

(1)Rise in step of technology
The step of technology in computer system is termed as generation of computer.Simply the generation of computer Each generation is distinguish from others on the basis of the type of switching circuits.
There are five generation of computer:

Generation Duration Components
First 1943-1958 Vacum tubes
Second 1959-1965 Tansistors
Third 1966-1973 IC-chips
Fourth 1974-Till Mcro -chips
Fifth Future Bio chips




First generation of computer
The first generation of computer were developed in 1943-1958 A.D.They use the vacuum tubes as the switching device.Lee De forest first developed vacuum tubes.

#Features of first generation of computer.
1)Very long in sieze,very slow.
2)Consume high power & produce large amount of heat.
3)They have slow speed,operating & limited computing & storage capacity (1-4B)1024+1024 Byte.
4)Programming was done in machine level language.
5)Programming was difficult & expensive eg:ENIAC,EDVAC,UNIAL,IBM650IBM701 e.t.c.


Second generation of computer
The second generation of computer was developed during 1959-1965 A.D.Tey use they use the transistors as the main switching device.John Barden &Willium B.shockley developed.

Features if seeond generation of computer
-They were smaller than first generation of computer
-They consumed less power & produced less heat in comparism to first generation of computer.
-They are faster & more reliable in processing.
-Less costly & capable of storing largeamount of data.
-Programming would be done in high level language like ‘CBOL’(Common Business Oriented Language)
-the operating speed was in terms of microsecond. eg:IBM 1401,IBM1620,CDC3600,CDC1804 e.t.c.

Third generation of computer
The third generation of computer was generated/developed during 1966-1973.They used IC Chips as the major components.Jack Clair Kilby developed it.
An Ic Chip is a circuit with number of transistors integrated on a small silicon chip.The main features of this generation of computer are as follows:
-They are small efficient & reliable.
-Operating speed was in terms of nano second.
- Semi-conductor memory was used as primary memory, magnetic disk was used as secondary memory.
-Understanding large numbers of high level languages eg:FORTAN(Formula Translation Pascal )e.t.c.-Input & output devices such as keyboard & moniters were used Eg: IBM 360,IBM 370,ICL 1900,VAX 750PDP-II