1. GrowMore B.C.A College
Computer Organization (Unit-1) B.C.A. Sem-1
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 Generation of computer
 ‘Generation’ of computer means this will give the basic information about the technologies
development trends in computer in the past and expected in the future.
 The generation means it is ‘step’ forward in technology.
 In the past you will find that the earliest computers were big in size, used a lot of power and
heated up quickly. For this reason it had to be shut down, end it needed cooled first.
 They were very expensive in terms of development and maintenance.
 As technology improved, computers become solid, faster and more powerful.
 From user’s point of view it becomes user friendly and more affordable.
1] First generation:
 The first generation starts from 1951 and end to 1958.
 Computers had vacuum tube, registers, and welded metal joints.
 They were large, slow, and expensive and produce a lot of heat.
2] Second generation:
 The second generation starts from 1958 and end to 1963.
 Computer used transistors (transistor is used to control the flow of electricity) invested by
john bardan, welter Brattain and William Shockley of bell laboratories.
 A transistor is a small, solid-state component designed to monitoring the flow of electric
current.
3] Third generation:
 The third generation starts from 1963 and end to 1974.
 The computer goes towards on new technology called the integrated circuit with SLSI (super
large scale integrated) and MLSI.
4] Forth generation:
 The forth generation starts from 1974 and end to 1989.
 Intel Corporation designed the first tiny computer on a chip.
 It was called a microprocessor.
 A microprocessor is an integrated circuit built on a tiny piece of silicon.
 It contents thousands or even millions of transistors.
5] Fifth generation:
 The third generation starts from 1989 to still date.
 Today computer are involved in fifth generation because they are all faster, cheaper, and very
small compare to all generation PCs.
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2. GrowMore B.C.A College
Computer Organization (Unit-1) B.C.A. Sem-1
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 Major Parts of Digital Computer
 The digital computer system has main three important parts
1. Input unit
2. Output unit
3. Central processing unit (CPU)
 In addition to these, secondary storage device are used to store data instructions on long
term basis.
1] Input Unit
 Data and instruction must be entered into the computer system.
 Input unit is a device which used to communicate with the computer system.
 Input of any form is just converted in to BITS (BInery degiTS) that easily understand by
processing unit.
 That input units/ devices are keyboard. Mouse, joysticks, touch screen, etc.
2] Central Processing Unit (CPU)
 Processing unit is also known as processor or CPU (Central Processing unit).
 It is also know as a heart of computer.
 It very fast and powerful then other parts of the computer.
 The CPU itself made of three components
1) Arithmetic logical unit (ALU)
2) Memory unit (MU)
3) Control unit (CU)
 Arithmetic logical unit (ALU)
 It perform arithmetic functions like addition, subtraction, multiplication, division and also
logical operation like grater then, less then and equal to.
 It completes all the operation with very high speed.
 It consist a number of registers to store temporary data.
 Memory unit (MU)
 The memory unit is used to store data and information.
 After the completion of an operation, the output is stored into memory.
 Control unit (CU)
 The control unit directs all the operation inside the computer.
 The function of the control unit is to execute the instructions of a program, one by one, in
the desired sequence.
 It’s controlling the instruction of units like input, output and storage.
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3. GrowMore B.C.A College
Computer Organization (Unit-1) B.C.A. Sem-1
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 Output unit
 Output unit works just in reverse manner then input units.
 It sends the information form inside the computer to the outside world.
 Basically, the output can classify by two ways…
o Hard Copy (direct usable from printed copy)
o Soft Copy (indirect usable from CD)
 The output can be converted to understand easily with any type for human being like…
o On the screen by monitor
o In printed paper by printer
o In graphic form by plotter
o In sound by speaker
 That Output units/ devices are Monitor, printer, plotter, speaker, etc.
 Storage unit
 Storage unit is used to holding the data information or instructions.
 There are two types of storage units
 Primary Storage unit
 A unit which is typically used in the computer or directly connected to CPU is called
primary storage unit.
 Ex: Register, cache memory, RAM
 Secondary Storage units
 A unit which is specially used outside the computer or indirectly connected to CPU, is called
secondary storage unit.
 Ex: CD (Compact Disk, HDD(Hard Disk Drive), FDD(Floppy Disk Drive), etc.
 Hardware:
 Hardware’s are all the physical parts of a computer system that we can see and touch.
 Beside the main box of the computer system, hardware also includes input devices, such as
keyboard, and mouse, storage devices like hard disk. Floppy disk and output devices like
monitor and printer.
 Software:
 Software’s are the electronics instruction that tell the computer what is to be done.
 The first software that runs the computer system is called the operating system. It also
known as OS or system software.
 Other software programs, called application program, help us accomplish specific task like
word processing. E.g. Microsoft office word, etc.
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4. GrowMore B.C.A College
Computer Organization (Unit-1) B.C.A. Sem-1
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 Application and system Software:
 System software:
 System software that controls and supports the operation of a computer system as
it performs various information processing task.
 It can be subdivided in to two part
1. System management software
2. System development software
1. System management software:
 System management software is used to manage the hardware, software, network,
and data resources of a computer system during its execution of information
processing jobs.
 Example of system management software is different operating system.
 Operating system is an integrated programs that supervise the operation of the cpu,
controls the input/output storage function.
 An OS performs basic five functions.
- User friendly interface.
- Managing the hardware resources.
- Managing the files and data resources.
- Managing the tasks a computer must finish.
- Provide miscellaneous support service.
a) MS-Dos:
 CUI stands for character user interface.
 CUI OS manages and controls all operation based on commands.
 Microsoft released MS DOS (Microsoft disk operating system) in the year 1982 and
version was 6.22 released in 1994.
 MS DOS is not a user friendly. MS DOS is a single tasking operating system.
 It is difficult to learn because the user must remember all commands.
 Limited user work on it.
 We cannot see mouse pointer in MS DOS.
 In MS DOS new hardware cannot work properly and configured.
 MS DOS file name cannot longer then 8 character name.
 The extension names cannot be more then 3 characters.
 MS DOS uses FAT 16 file system.
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b) MS-Window:
 GUI stands for graphical user interface.
 The first window version released in 1985.
 MS-window is user friendly.
 MS-window is multi tasking operating system.
 In window multiple users can work at a time on the same operating system.
 In MS-windows, we can see the mouse pointer for clicking any item.
 In MS-windows detects hardware and installs software for hardware automatically.
 MS-window has a longer file name and extension.
2. System development software:
 System development software helps as specialists and end users development computer
software and information system procedures.
 E.g. language translator, programming editors, and other programming tools.
I. Programming languages is a collected variety of programming packages to help
programmer develop computer programs. The five major levels of programming
languages are machine level language, assembler language, high level language, forth
generation language and object oriented languages. object oriented language like
java and special purpose language like HTML and XML are being wildly used for web
based business application.
II. Language translator programs used to convert programming language instructions
into machine language instruction codes.
III. Editors are used for editing the new as well as existing programs E.g. notepad,
WordPad.
 Application software:
 Application software that directs the performance of a particular use, or application, of
computers to meet the information processing needs of users.
 It includes a variety of programs that can be subdivided in to (1) general purpose (2)
special purpose software.
1. General purpose application programs perform common information processing
jobs for end users. Example is word processing, database management, and
presentation of graphics programs.
2. Special purpose programs accomplish information processing tasks that support
specific business function or process, scientific and engineering application; games
are most popular forms of application software.
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6. GrowMore B.C.A College
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 Classification of computer:
 Super computer:
Def: They are used for complex scientific computation is known as super computer.
Description: Very large size and very high speeds characterize them. The word length for
these computers is more then 64 bits.
Example: Cray 1/2/3, PARAM 10,000.
Application: They are used in weather forecasting in nuclear power plants, in defuse, in
medical, in electronic design, in energy management etc.
Features: More then processing unit
Perform parallel processing.
Very high processing speed and large in a size
 Mainframe computer:
Def: A high capacity computer but lesser then super computer and it mainly used for bulky
data handling and information processing is called a main frame computer.
Description: it is also called predecessor of servers because they support multi users. It
would occupy a entire room and could cost over million dollars.
Example: IBM 3090.
Application: it is used the purpose of research, engineering works, and graphics. E.g.
railway and air station.
Features: Provide a maximum I/O connectivity
Provide a maximum I/O band width.
Very good single thread operation.
 Mini computer:
Def: it is very small and slower then mainframe computer, so it is called a mini computer.
Description: they have many terminals connected to support many users. It is also called
midrange computer.
Example: PDP-I, VAX.
Application: distributed processing, multiprocessing application.
Features: midsize computer.
Multiprocessing system capability.
Supporting up to 200 users simultaneously.
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7. GrowMore B.C.A College
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 Personal computer:
Def: The smallest category of computer which used micro processor as its CPU is called
microcomputer. It is also called a PC (personal computer)
Description: the speed and its capacity of processing are limited for personal use only.
They are small enough to fit in a desk so it is called a desktop.
Example: Pentium III .
Application: it is used for the personal purpose of writing latter, calculate and for product
presentation.
e.g. office, account department, in company and other area.
Features: it has a limited memory and processing power.
Provide a limited I/O connectivity
Provide a max I/O band width.
 Analog and digital waves
 Analog wave:
 Analog electronic uses voltage, current or frequency that can be any value.
 The voltage often changes smoothly from one value to another value.
 E.g. dimmer light switch up or down.
 Analog signal that change with time is describe below.
 Digital wave:
 The term digital means that the signal is limited to only a few possible values.
 The general, digital signals are represented by only two possible voltages on wire 0
volts and 5 volts.
 The digital electronics use o volt as “low” or false or “0” and 5 volt as “high” or true or
“1”.
 In digital computer, 0 and 1 digit known as BITS ( BInary DigTS ).
 Digital signal that change with time is describe below.
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