BLOCK DIAGRAM OF COMPUTER

CPU

CONTROL UNIT

ARITHMETIC &
INPUT OUTPUT
LOGIC UNIT

MEMORY UNIT

INPUT
Input unit gets data and instructions from the user and then transmit them
into the memory. The input unit contains different devices.
e.g:- Keyboard, Mouse, Scanner, Joystick, Light pen, Microphone etc.,
It performs three major functions
• Gets data from the user.
• Coverts the data into machine readable form.
• And then transmit the data into main memory of computer

CPU (Central Processing Unit)

• CPU is the brain of the computer. It consists of memory unit, ALU and
control unit.
• ALU (Arithmetic and logic unit)
• It performs arithmetical operations like addition, subtraction ,
multiplication and division.
• It is also responsible for performing logical operations like AND, OR,
Equal to, Less than etc.,
• In addition to this it also performs merging, sorting and selection of given
data.
CU- Control Unit
• It is the supervisor of all the other units
 • It transfers the data from memory and from memory to ALU.
• The memory unit sends a set of instructions to the control unit.
• The control unit converts those instructions into signals and controls all
the activities inside the computer.
• Transfers the result from memory to output device.
• Memory unit
• All the data has to be processed or has been processed is stored in the
memory unit. It transmits it to the required part of the computer
whenever necessary.
Two type of Computer memory
Primary memory
▪ It is a temporary memory.
▪ Data gets erased once the power is switched off.
▪ Cannot store large amount of data.
▪ e.g:- RAM (Random Access Memory)
▪ It is used for reading and writing purposes.
▪ Data has to processed, first transferred to RAM and then to CPU.
Secondary Memory (Permanent memory)
▪ For permanent storage of datas, Secondary memory is used.
▪ Even in power failure data does not get erased easily.
▪ e.g:- Hard disk
OUTPUT
• The output unit gets the output results from the memory in the form of
binary. It then converts it into human readable form and displays the
result.
• It displays the result either in the form of soft copy (or) hard copy.
• e.g:- Monitor, Printer, VDU (Visual Display Unit), Plotters, Speakers etc.,

CHARACTERISTICS OF COMPUTER

MEMORY SPEED

AUTOMATION Characteristics of Computer ACCURACY

RELIABILITY VERSATILITY DELIGENCE

SPEED
Computer works with high speed. Computers can process million instructions
per second. Speed is measured in nanoseconds and microseconds.
STORAGE
Datas are stored in computer’s Primary memory which can be got back any
time. Datas are also stored in secondary storage such as CDs, Pendrives etc.,
DELIGENCE
Computers can work for long hours without getting tired. It performs millions
of tasks with same speed and accuracy.
VERSATILITY
Computer is a versatile tool. We can use computer for business, scientific
applications etc.,
AUTOMATION
Automation is the ability of computer to do given work automatically.
ACCURACY
Computers are 100% accurate. They do not make mistakes. Errors occurred due
to users only.
RELIABILITY
A Computer is reliable as it gives consistent result for similar set of data. (i.e) if
we give same set of input any number of times we will get the same result.

GENERATION OF A COMPUTER

GENERATION PERIODS MAIN COMPONENT USED

First generation 1940 – 1956 Vacuum tubes

Second generation 1956 -1963 Transistors
Third generation 1963 -1971 Integrated Circuits
Fourth generation 1971 – 2010 Microprocessor
Fifth generation 2010 – Till date Artificial intelligence
First generation : (1940 – 1956)
• Vacuum tubes (or) thermionic valves are used.
• Big in size.
• Consumed more power.
• Malfunction due to overheat.
• Worked on the basis of binary coded concept (0’s and 1’s).
• Input: Based on punched cards and paper tape
• Output: Displayed on printouts.
e.g
ENIAC (Electronic Numeric Integrated Computer)
EDVAC (Electronic discrete Variable Automatic Computer)
UNIVAC (Universal Automatic Computer)
Second generation:(1956 – 1963)
• Transistors are used.
• Generates less heat and power when compared to first generation
computers.
• Size was smaller than first generation computer.
• Computing time was also less.
• Programming languages are used. FORTAN, COBOL etc.,
• Input and output: punched cards and magnetic tapes were used
• Memory: Magnetic core / magnetic tape
Third generation: (1963 – 1971)
• Integrated circuits were used
• Computers were smaller, faster and more reliable.
• High level languages were used.
• Consumes less power and generates less heat.
• Easier for commercial use.
• Mini computers were introduced.
Fourth generation (1972 – 2010)
• Developed using microprocessor.
• Very small in size and portable.
• Faster and produces more accurate results.
Fifth generation (2010 to till date)
• High capability and large memory capacity.
• Fast and performs multiple tasks simultaneously.
• Advanced technologies of fifth generation
Artificial intelligence, Parallel processing, Nanotechnology, Quantum
computation etc.
APPLICATIONS OF COMPUTER
• Home
• Medical field
• Entertainment
• Industry
• Education
• Banking
• Business
Home:
At home, Computers are used for
• Online bill payment.
• Social media Access.
• Home tutoring and online class.
• Watching movies and shows.
• Work from home facility, to corporate employees.
• Internet access and E-mail.
• Playing games.
Medical field
Computers are used at hospitals,
• To maintain the database of patients, diagnosis and X-rays.
• Now a days, robotical surgical devices are used to perform delicate
operations.
• Virutal reality techniques are used for training purpose.
• Live monitoring the patients, to monitor the movements of fetus inside
mothers’ womb.
Entertainment:
Computers are used to,
 • Play games online (Virtually).
• Watch movies online.
• Listening to music, movies etc.
• In recording field, artificial instruments are used to record music with the
help of computers.
e.g: MIDI instruments (Musical Instrument Digital Interface) , Photo editing.
Industry:
Computers are used in industries to perform several tasks like
• Managing inventory
• Designing purpose
• Creating virtual sample products
• Interior designing
• Stock markets etc.,
Education
Computers are used in education field for the purpose of,
• Online classes
• Online examination
• Referring e-books
• Use of audio visual aids get increased
Government
In government sectors computers are used for
• Data processing
• Maintaining a database of citizens
In defense field computers are used for,
• Missile development
• Satellite, Rocket launches etc.,
Banking
In banking sector computers are used,
• To store details of customers
• Online transactions
• ATMs (cash deposit and withdrawal)
• Manual errors get reduced.
Business
In business field computers are used for
• Transaction processing
• To analyze investments, sales, expenses etc.,
• Training
• Computer based trainings reduces the time and travelling costs
• e.g: video conferencing
Arts
Computers are used in dance, photography, arts and culture.
• In dance field, fluid movements of dance can be shown via animation.
• Science and Engineering
• Super computers are used in Research and Development field.
• Topographic images can be generated with the help of computers.
• Detailed analysis of earthquakes are possible.

TYPES OF COMPUTER
Classification of computer on the basis of working
• Analog Computer
• Digital Computer
• Hybrid Computer
Analog Computer
• Analog computers are used to process analog data.
• Analog data’s are continuous in nature and having an infinity value
e.g., Temperature, Pressure, Speed, Weight, Voltage, Depth etc.,
• It directly accepts the data from the measuring device without converting
it into numbers and code.
• Analog computers do not require any storage capability because they
measure and compare quantities in a single operation.
• Produces output in the form of graph (or) series of dial (e.g., Speedometer
of a Car).
Applications
• Engineering and scientific application
• Paper making, Chemical industry
 • Oil refinery (for measuring flow and temperature)
e.g., Slide rule, Differential analyzer
DIGITAL COMPUTER
• A digital computer works with digital value (binary) 0’s and 1’s.
• Digital computer process information on the basis of presence (or)
absence of an electric charge.
• Digital computers are used to process numeric as well as non-numeric
data.
• It performs arithmetic and logical operations.
• It has storage section.
• Offers high speed as the data is processed digitally.
e.g., Accounting machines, Calculator, Desktop, Laptop
HYBRID COMPUTER
• Hybrid computer is a combination of analog and digital computer.
• It has the speed of analog computer and the memory and accuracy of
digital computer.
• Used in specialized applications where both analog and digital data is
processed.
• e.g., Processor used in petrol pump converts the measurements of fuel
flow into quantity and price.
o At hospitals, in ICU analog device is used to measure patient’s
blood pressure and temperature which is then converted and
displayed in the form of digits.
• Used for scientific calculations, in defense and radar systems.
Classification of computers on the basis of size
• Super Computer
• Mainframe Computer
• Mini Computer
• PCs (or) Micro Computers
SUPER COMPUTER
• Powerful computers that can process large amount of data and
computation very quickly
• Speed is measured in FLOPS (Floating point operations per second)
Used in
• Science
• Defense
• Engineering
• Aerospace
• Education
Computers having multicore processor and general purpose graphics processing
units are called Desktop Supercomputers (or) GPU Supercomputer.
Applications
• Weather forecasting
• Scientific simulation (labs)
• Military agencies
• Cryptanalysis
• Climate research
• Oil and gas exploration
• Quantum mechanics
Mainframe Computer
• Large and expensive.
• Handles huge volumes of information and data.
• Provides great security against the attack of viruses.
Used in
o Institutions
o Research
o Academics
o Healthcare
o Libraries
o Financial institutions
o Large business
o Stock brokerage firms
o Insurance agencies
Used for tasks related to,
Census taking, Industry and consumer statistics, Enterprise resource planning,
Transaction processing, e-business and e-commerce
Mini computer
• Performs data processing activities in same way as the Mainframe but on
a smaller scale
• Cost is low
• Intermediate in size, power, speed, storage etc.,
• Used by small organizations
• In recent year, minicomputers are called as small (or) midsize server
Server
Server is a central computer that provides information to other computers.
Workstation
• A Workstation refers to an individual computer or group of computers
used by single user to perform work.
• Workstations are capable of multitasking
• It has one or more high-resolution monitors and a quicker processor
than a personal computer
• Workstations have advanced graphic capabilities, large storage
capability and powerful central processing unit.
Microcomputer
• Microcomputers are also called as portable computer.
• Microcomputer uses a single microprocessor for its CPU.
• It is a low cost small digital computer.
• Maximum speed of microcomputer is up to 1million bytes per second.
Desktop Computer
• It is also known as personal computer.
• It can be placed on the desk.
• It consists of CPU, keyboard and mouse as input units, monitor or
display unit as an output device.
• The CPU consists of microprocessor, main memory, secondary storage
unit like hard drive, optical drive, power supply unit that is housed in a
single cabinet.
Laptop Computer
• A laptop computer (or) notebook computer is a small, portable personal
computer with a screen and alphanumeric keyboard.
• It runs on AC power (or) battery that lasts for hours.
 • They basically have an LED or LCD screen.
• In laptops, the keyboard, CPU, monitor, and mouse all are in-built.
• Light in weight and small to carry.
Palmtop Computer
• A palmtop computer was an approximately pocket calculator sized,
battery operated.
• It has integrated keyboard and display. (clamshell design)
• It is also known as PDA(personal digital assistant), hand-held computers
and pocket computers.
• Due to small size, most palmtop computers does not have disk drive.
• Palmtop PC comes with Intel compatible X86 Processor and IBM
compatible PC architecture.
• All of these devices were DOS based, which was kept in ROM.
• Most of the PCs could run standard, off-the-shelf PC software with no or
little modifications, even though many came with a variety of PDA and
office apps pre-installed in ROM.
• Some Palmtop PCs could run on other OS such as GEOS, Windows 1.0-
3.0 (in Real mode only) or MINIX 2.0.
Classification of computer on the basis of processor XT,AT
The older 8bit systems are very different. They give us two basic system
types (or) classes of hardware.
• 8 bit (PC/XT) class system
• 16/32/64 bit (AT – class) system
8bit (PC/XT – Class) Systems
• The first generation of IBM PCs.
• These kind of PCs include floppy disk based PC and hard disk based
PC.
• It had an 8-bit 8088 processor.
• For system expansion, it follows 8-bit Industry Standard Architecture
(ISA).
• The ISA bus in PC/XT systems can send and receive only 8bits of data
in a single cycle.
16/32/64 – bit (AT-Class) system
• The first AT-class system had 16-bit ISA bus (Extension of 8bit ISA
bus).
• They have 16-bit or greater system bus.
• AT class system must have processor that is compatible with Intel 286
(or) higher processors.
• It also includes 386, 486, Pentium, Pentium pro, Pentium II, Pentium
III processors.
• The bus architecture includes basic memory architecture, interrupt
request (IRQ), direct memory access (DMA) and IO port address
design.
Various Expansion slots (or) bus designs are,
o 16-bit ISA bus.
o 16/32- bit Extended ISA bus.
o 16/32- bit PS/2 Micro Channel Architecture(MAC) bus.
o 16-bit PC-Card (PCMCIA) bus.
o 32-bit Card bus (PCMCIA) bus.
o 32-bit VESA Local (VL) bus.
o 32/64-bit Peripheral Component Interconnect bus.
o 32-bit Accelerated Graphics Port.
• AT type systems with 386 (or) higher processor have special
capabilities which was not found in first generation (or) 286 based
Ats.
• The special capabilities include memory addressing, memory
management.
• It can access 32 (or) 64 – bit wide data.
• Most of the systems with 386DX (or) higher chips have 32-bit bus
architecture. It has the capability to transfer 32-bit data.
 Differences between PC/XT and AT Systems
System Attributes (8-bit) PC/XT (16/32/64 – bit) AT Type
Type
Supported Processors All x86 or x88 286 or higher
Processor modes Real Real/Protected/Virtual Real
Software supported 16-bit only 16 (or) 32-bit
Bus slot width 8-bit 16/32/64-bit
Slot type ISA only ISA, EISA, MCA, PC-Card,
Cardbus, VL-Bus, PCI and
AGP
Hardware interrupts 8 (6 usable) 16 (11 usable)
DMA Channels 4 (3 usable) 8 (7 usable)
Maximum RAM 1MB 16MB/4GB or more
Floppy controller speed 250Kbps 250/300/500/1,000 Kbps
Standard boot drive 360KB or 720KB 1.2MB / 1.44MB / 2.88MB
Keyboard interface Unidirectional Bidirectional
CMOS memory / clock None standard MC146818-compatible
Serial – port UART 8250B 16450/16550A or greater

Core i3 Processor
• Entry level processor.
• Not suitable for heavy multi-tasking such as video editing.
• Dual core processor.
• Most commonly used in laptops for low power requirements and low
heat generation.

Core i5 Processor
• Mid range processor.
• Available in dual core and quad core.
• Performs multi-tasking.
• Used in desktops and laptops.
• Used for moderate high performance applications.
 Core i7 Processor
• High end processor.
• It is powerful and very high performance processor.
• Has built in Intel HD Graphics processor that provides better
performance in video editing, gaming etc.
Core i9 Processor
• High performance processor.
• Performs heavy multi-tasking such as gaming , content creation
and editing large videos.
• 16 core processor.

MEMORY
Memory unit is the amount of data that can be stored in the storage unit. The
storage capacity is expressed in terms of Bytes.
Bit - Binary digit
Nibble - A group of 4bits
Byte - A group of 8 bits. Byte is the smallest unit that represent a data item or
character.
Kilobyte (KB) – 1KB = 1024 bytes
Megabyte (MB) – 1MB = 1024 KB
Gigabyte (GB) – 1GB = 1024 MB
Types
• Primary Memory
• Secondary Memory
Primary Memory
• Primary memory is also known as main memory.
• It is a memory that a processor or computer accesses first or directly.
• It is a volatile memory.
• The information kept in primary memory is lost when the computer shuts
down (or) loses power.
 Types of Primary memory
PRIMARY MEMORY

RAM ROM

PROM

SRAM DRAM
EPROM

EEPROM

RAM
• Random Access Memory contains one (or) multiple memory modules
that store data temporarily.
• RAM doesn’t save data when the computer is shut down.
• When we are launching the software, then it is loaded into RAM.
Types
• SRAM
• DRAM
SRAM
• Static Random Access memory.
• It is speedier and more efficient.
• Uses flipflops as storage medium.
DRAM
• Dynamic Random Access memory.
• It is simple and easily affordable.
• DRAM uses capacitor as storage medium.
ROM (Read Only Memory)
• ROM is a primary memory.
• Processors only read the content of ROM but cannot change the content.
PROM
• Programmable Read Only Memory.
• Once you program the information it cannot be altered.
• It is nonvolatile. It can retain its content when the computer is turned off.
EPROM
• Erasable Programmable Read Only Memory.
• The data can be erased and reprogrammed by using ultraviolet (UV) light.
EEPROM
• Electrically Erasable Programmable Read Only Memory.
• The data can be erased and reprogrammed by using electrical signals.
• Faster than flash memory.
Primary storage is limited in size. In modern PC, primary storage is often
around 4GB in size.
DDR (Double data rate)
• Transfers data on the rising and falling edges of the clock signal, allowing
for faster data transfer rate.
• This is also known as double pumped, dual pumped, double transition.
• Toggle mode is used in NAND flash memory.
SECONDARY STORAGE
• The secondary storage media can be fixed or removable.
• Fixed Storage media
• It is fixed inside the computer. E.g: Hard disk
• Removable Storage media:
• It is portable and can be taken outside the computer.
Secondary Memory

Sequential access device Direct Access Device

Magnetic disk Optical disk

Magnetic tape

I) Hard disk I) CD
II) Zip Disk II) DVD
III) Floppy disk III) Blu ray DVD
HARD DISK DRIVE
A hard disk drive (HDD) is an internal or external computer component that
stores data such as operating system, applications and user files.
HDDs are non-volatile storage devices.
• An HDD includes two main elements a spinning platter and an actuator
arm.
• The platter is a circular magnetic disk containing track and sectors that
retain data.
• The actuator arm moves across the platter to read and write data.
• The platter and actuator arm are protected by air sealed metal casing.
• A circuit board is present on the back of the hard drive to communicate
with the computer.
Advantages of hard disk
• We can store large amount of information.
• Access speed is high.
• Storage is permanent.
• Cost is low.
SSD (Solid State Drive)
• New generation of storage devices.
• SSD are made using NAND flash memory.
• SSD has no moving parts.
• SSD is a non-volatile storage device.
• Stores data in ICs
The difference between SSD and HDD is, SSD stores the data in integrated
circuits and HDD stores data magnetically through the spinning disks. Now a
days most of the PC’s and laptop come with SDD. More expensive than
HDD but it has higher speed and more energy efficient.It has high storage
capacity ranging from 32GB upto 8TB (Terabytes).
COMPACT DISC (CD)
• A compact disc is a circular memory device made up of plastic.
• It is used for storing datas and can be accessed later.
• It is 4.5 inch (12cm) in diameter.
• It can store data up to 700MB (or) 80minutes of audio.
History
Sony and Philips proposed CD standards. Philips factory in Germany created
firs CD on 17th August 1982. In 1993 CD technology was introduced to US.
Working
• It stores data as small notches.
• It reads data with the help of laser beam.
• Drives converts notches into usable data.
Uses:
To store software programs and then it can be installed on to the computer.
DVD
• Digital Versatile Disc (or) Digital Video Disc.
• It is used for storing optical data.
• It can store upto 17GB data.
• Size of DVD is same as CD, but DVD has more storage capacity.
• DVD can provide a definition of 720x480 pixels.
History
DVD was co-developed by Sony, Panasonic, Philips and Toshiba in 1995.
Types
• DVD-ROM
• DVD-R
• DVD-RW
DVD-ROM (Read only)
• It is also known as non-writable DVD.
• Datas on this kind of DVDs cannot be erased (or) added.
• E.g: Movie DVDs
DVD-R (Writable)
• Datas can be written (or) recorded only once.
• When its storage gets full, it becomes a read-only DVD.
DVD-RW (Rewritable (or) Erasable)
• These kind of DVDs can be erased, written (or) recorded multiple
times.
BLU-RAY DVD
• High capacity optical disc.
• Used for storing high definition video and large amount of data.
• Developed by Blu-ray Disc Association (2006)
• It uses blue laser (Blue violet) which has short wavelength(450nm).
This allows for higher data storage capacity on a single disc.
• CDs and DVDs uses red laser whose wavelength is 650nm.
Types
• Single layer – 25GB.
• Double layer – 50GB.
• Triple layer – 100GB.
• Quadraple layer – 128 GB.
Blu-ray disc provides a definition of 1920x1080 pixels.
PEN DRIVE
• Pen drive is a compact secondary storage device.
• It is also known as USB flash drive, thumb drive, jump drive (or) USB
Stick.
• It is connected to computer via USB port.
• It is a plug and play device, because it doesn’t need additional
software (or) hardware to use it.
Parts
It consists of integrated circuit memory chip to store data. This chip is placed
inside a plastic (or) aluminium casing.
Storage capacity
Generally ranges from 2GB to 128GB.Now a days, it is available to hold data
between 8GB to 2TB.
Brands
SanDisk, Kingston, Transcend, HP, Sony etc.
Uses:
Pen drives are commonly used for storage, data backup and transferring files
between devices.
MAGNETIC TAPE
• It is a sequential data secondary storage medium made up of flexible
polyester material.
• One side of the tape is coated with magnetic material.
• Group of data stored and arranged in a tape is called records.
• Vertical divisions of a tape along with length are called frames.
• Group of records is called as blocks.
• It consists of several number of tracks.
• Both parallel recording and serial recording of data can be done.
• Inter record gaps are those which separate the blocks on the tape.
Recording mechanism:
In serial recording, the first set of bits are recorded along with the whole
length of the tape. Once the end of the tape is reached, the recording head
will be repositioned to record a new track. During this process, it will
record in opposite direction. This process will be continued until the tape
is full. The magnetic tape can be
Advantages:
• It is inexpensive.
• It can store large amount of data.
• It provides large backup.
Disdavantages:
• Slow due to sequential access of data.
• Stored data cannot be easily updated or modified.
• It requires caring to store.
ZIP DISK
• Zip disk is an advanced version of the floppy disk (1.44”) developed
by Lomega.
• The disk needed a special drive called Zip drive.
• Zip disks were available in 100MB (or) 250MB capacities.
• The lomega zip disk is bigger than floppy disk and made up of hard
plastic.
• The zip disk contains a magnetic circular disk to hold information.
• To read and write information on zip disk, it is inserted into zip drive.
• With the introduction of new and large storage capacity mediums like
CD-R, CD-RW the zip disk disappeared from the market.