Transcript uNIT-1 - Computer Science Engineering

ASICS
 An ASIC (application-specific integrated circuit) is
a microchip designed for a special application, such as
a particular kind of transmission protocol or a handheld computer. You might contrast it with general
integrated circuits, such as the microprocessor and the
random access memory chips in your PC. ASICs are
used in a wide-range of applications, including auto
emission control, environmental monitoring, and
personal digital assistants (PDAs).
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• An
application-specific integrated circuit,
is
an integrated circuit (IC) customized for a particular use,
rather than intended for general-purpose use.
• An ASIC can be pre-manufactured for a special application
or it can be custom manufacture for a particular customer
application.
• For example, a chip designed to run in a digital voice
recorder is an ASIC.
• Application-specific standard products (ASSPs) are
intermediate between ASICs and industry standard
integrated circuits like the 7400 or the 4000 series.
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 an ASIC has grown from 5,000 gates to over 100
million. Modern ASICs often include
entire microprocessors, memory blocks
including ROM, RAM, EEPROM, Flash and other large
building blocks. Such an ASIC is often termed a SoC
(system-on-chip)
 Designers of digital ASICs use a hardware description
language(HDL), such as Verilog or VHDL, to describe
the functionality of ASICs.
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HISTORY OF ASICS
 The initial ASICs used gate array technology.
 Ferranti produced perhaps the first gate-array, the
ULA (Uncommitted Logic Array), around 1980.
 An early successful commercial application was the
ULA circuitry found in the 8-bit ZX81 and ZX
Spectrum low-end personal computers, introduced in
1981 and 1982. These were used by Sinclairv
Research (UK)
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 Due to Customization occurred by varying the metal
interconnect mask. ULAs had complexities of up to a
few thousand gates.
 Gate Array Design:
 Gate-array design is a manufacturing method in which
the diffused layers, i.e. transistors and other active
devices, are predefined and wafers containing such
devices are held in stock prior to metallization in other
words, unconnected.
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 Gate-array ASICs are always a compromise as mapping
a given design onto what a manufacturer held as a
stock wafer never gives 100% utilization.
 Often difficulties in routing the interconnect require
migration onto a larger array device with consequent
increase in the piece part price.
 These difficulties are often a result of the layout
software used to develop the interconnect.
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ASICS SUPPLIERS
 There are two different types of ASIC suppliers, IDM and fabless.
IDM ASIC suppliers
 Allegro
 AMS
 Avago Technologies
 Elmos Semiconductor
 Cavium Networks
 Fujitsu
 Freescale Semiconductor
 HITACHI
 Global Foundries
 IBM
 Infineon Technologies
 GigOptix (ChipX Structured ASIC)
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LSI Corporation
Maxim Integrated Products
NEC
NXP Semiconductors
ON Semiconductor
Renesas
Samsung
STMicroelectronics
Texas Instruments
Toshiba
TSMC
Bosch
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Fabless ASIC suppliers
 Alchip
 Aeroflex Colorado Springs
 AnSem (Analog, RF and mixed-signal ASICs)
 Brite Semiconductor
 Broadcom Corporation
 Custom Silicon Solutions, Inc.
 GigOptix (ChipX Structured ASIC)
 DA-Integrated
 DELTA Microelectronics
 eASIC
 eSilicon
 Faraday Technology
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Hong Kong Science and Technology Parks Corporation
ICsense (ASIC Design and Supply)
Marvell Semiconductor
MOSIS
Nvidia
Open-Silicon
PMC Sierra
Qualcomm
SWINDON Silicon Systems
Socle Technology Corporation
Triad Semiconductor (Configurable Analog and Mixed-Signal)
Xilinx
Cactus Semiconductor
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•Computer is an electronic device that perform some
arithmatic and logic operation to achive specific task.
•Computer works mostly on data and information.
•Data is a collection of raw facts.Data may be valuable or
non-valuable.
•Information is the processed data.
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Major Components Of A Digital
Computer
Input Device
CPU
Output Device
Memory
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CPU
 The CPU is the brain of the computer
 Its primary function is to execute programs.
 It also control the operation of all other components such
as memory, input & output devices.
Accumulator
ALU
General &
Special Purpose
Register
Control Unit
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CONTROL UNIT
 It control the entire operation of the computer by passing
control signals.
 It gives order to ALU what operation is to be performed .
 It controls the data flow between the CPU & Peripherals.
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Characteristics Of Computer
 Speed
 Accuracy
 Reliability
 Storage Capability
 Automation
 Versatility
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Characteristics Of Computer
 Computers are built to carry out a small variety of
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instruction.
Instruction are extremely simple e.g. add,subtract,read
or write chracter,compare a no. etc.
Most instruction are carried out in less than a
millionth of a second.
Instructions are carried out obediently with no
question asked.
Instructions are carried out without any mistakes.
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Disadvantages of computer
 Computer does no work by itself. It works on the basis of
the list of instruction given to it.
 Computer doesnot have any I.Q it works on the basis of
what has been instructed.
 Computer does not take decision of its own.
 Computer does not learn by experience.
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ALGORITHM
 It is a step by step description of how to arrive at the
solution of the given problem.
 An algorithm may be defined as a finite sequence of
instruction to solve a problem.
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Characteristics of algorithm
 An algorithm begins with instruction to accept input.
 The proceesing rules specified in the algorithm must
be precise and unambiguous.
 Each instruction must be carried out by a person with
paper and pencil.
 The total time to carry out all the steps in the
algorithm must be finite.
 An algorithm must produce one or more outputs.
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Example of algorithm
 an algorithm to find the avg no. of vowels in a passage.
Step 1: Let no. of character=0
Step2: Let no. of vowels=0
Step3: Repeat 4,5,6 and 7 until end of passage is
reached.
Step4: read one character from passage.
Step5: add 1 to no. of character.
Step6:if the character is any one of the letters
A,E,I,O,U,a,e,I,o,u add 1 to no. of vowels.
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Step7:move to next character.
Step8: avg no. of vowels =
no.of vowels/no. of character
Step9: Write avg no.of vowels.
Step10: stop.
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Flow Chart
 It is a pictorial representation of an algorithm.
Start/Stop
INPUT/OUTPUT
Decision Box
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Processing
C
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Input Devices
• These are those devices, which facilitate a user to give
input. Information is entered in to a computer through
input devices.
• An input device converts input information in to suitable
binary format, which can be accepted by the computer
system.
• The computer system has to process details of each
command, therefore the command will have to be
converted in to machine readable format and this work can
be done through input unit.
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Keyboard
 Keyboard is one of the most widely used peripheral devices.
 Data is entered in to the computer system through keyboard.
 Keyboards are designed for the input of text and characters and
also to control the operation of a computer.
Most of the keyboard have a common number of features like:
 Standard type writer keys
 Function keys
 Special purpose keys
 Cursor Movement Keys
 Numeric keys
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MOUSE
 Mouse is a device which is used to move the cursor on the
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screen and to select options.
When the mouse is moved on the surface the cursor is also
moved in the same direction on the monitor.
By moving the mouse the user can point to menu on the
screen i..e. Mouse is also known as pointing device.
Pressing the button of a mouse is known as clicking.
Technicians often describe mouse speed in DPI(dots per
inch).
One DPI is intended to be the number of pixels the mouse
cursor will move when the mouse is moved one inch.
Some common types of mouse are
 Mechanical Mouse
 Optical Mouse
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LIGHT PEN
 A light pen is a pointing device.It is an input device in the
form of a light-sensitive wand used in conjunction with
the computer's CRT monitor.
 It allows the user to to select a displayed menu option on
the CRT.
 A light pen can work with any CRT-based monitor, but
not with LCD screens, projectors or other display devices.
 It is capable of sensing a position on the screen when its
tip touches it ,its photocell sensing element detects the
light coming on the screen and sends the corresponding
signal to the processor.
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TOUCH SCREENS
 It is a type of display screen in which one can use finger to
point the command displayed on the screen. In this user
touches the icon that represent their choices and the
computer display information about their choices.
There are some types of touch screen technology:
 A resistive touch screen panel is coated with a thin
metallic electrically conductive and resistive layer that
causes a change in the electrical current which is
registered as a touch event and sent to the controller for
processing.
 Surface wave technology uses ultrasonic waves that pass
over the touch screen panel. When the panel is touched, a
portion of the wave is absorbed. This change in the
ultrasonic waves registers the position of the touch event
and sends thisSunil
information
to the controller for processing.27
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JOYSTICK
 A joystick is also a pointing device.
 It is used to move cursor on the CRT screen.
 A joystick is a stick that has spherical ball at it’s upper as
well as its lower end.
 The lower spherical ball moves in a socket.
 The electronic circuitry inside the joystick detects and
measures the displacement from its central position, the
information is sent to the processor.
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MICR
 Magnetic Ink Character Recognition, or MICR, is a special
kind of character recognition technology that was adopted
mainly by the banking industry to facilitate the processing of
cheques.
 A special ink called magnetic ink is used to write the character
of the cheques and deposit forms which are to be processed by
an MICR.
 The magnetic ink is magnetized during the input process.
 The MICR reads these pattern and compared with the special
pattern stored in the memory
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OCR(Optical Character Reader)
 It is an abbreviated form of Optical Character Reader.
It detects the alphanumeric character printed on
paper.
 It works on the basis of light scanning techniques in
which each character is illuminated by the light source
and the reflected images of the character is received by
the photocells which provides binary data
corresponding to the lighted and dark areas.
 OCR is quite costly because the memory requirement
is very high.
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BAR CODE READER
 Bar code is a machine readable numerical code, printed as
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a set of varying width vertical bars.
A barcode reader is a computer peripheral for reading
barcodes printed on various surfaces.
As you know bar codes are present on most of the grocery
item, it consist of a number of thick lines with a varying
distance between them.
A barcode reader scans the bar code, and converts it into a
number that the computer can then process and display on
the screen.
Bar code reader, generally consists of a light source, a lens
and a photo conductor translating optical impulses into
electrical ones. Therefore, it read such bars and convert
thm in to electrical pulses which is processed by the
computer.
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OMR
 Special marks such as square or bubble are prepared on
examination answer sheets.
 The user fill in theses squares or bubbles with soft pencil
or ink to indicate there choices. These squares are detected
by an OMR and the corresponding signals are sent to the
processor.
 If a mark is present, it reduces the amount of reflected
light . If a mark is not present the amount of light reflected
is not reduced.
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OUTPUT DEVICES
The output devices receive information from the
computer and provide them to user in a readable
format. The computer sends information to the output
devices in binary coded forms. Then, output devices
convert them in to a form, which can be used by user.
Some output devices are
• Printer
• Monitor
• Plotter
• Speaker
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PRINTER
 It is a device that produces a hard copy which is permanent
human-readable text of documents stored in electronic form,
usually on physical print media such as paper or transparencies.
 The data received by a printer may be:
a string of characters
a bitmapped image
a vector image
 Printers which are used with computer can be classified in two
ways.
Line Printer
Character Printer
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Line printer is categorised into:
Drum Printer
Chain Printer
Comb Printer
Drum Printer
In drum printers, a drum carries the entire character set of the
printer repeated in each column that is to be printed. The
printer receives all characters to be printed in one line of the
text from the processor. The hammer hit the paper and ribbon
against the desired character on the drum when it comes in the
printing position.
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A
AAAAAAAAAAA
BBBBBBBBBBBB
B
--------------------------------------------------------------------------------------------------------
 In chain printers which is also known as train printers, the
character set is arranged multiple times around a chain that
travels horizontally past the print line. In either case, to print a
line, precisely timed hammers strike against the back of the
paper at the exact moment that the correct character to be
printed is passing in front of the paper. The paper presses
forward against a ribbon which then presses against the
character form and the impression of the character form is
printed onto the paper.
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 In comb printers, a comb of hammers printed a portion of a
row of pixels at one time. By shifting the comb back and forth
slightly, the entire pixel row could be printed.
 Another way of classifying the printer is on the basis of
manufacture:
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Impact Printer
Non Impact Printer
 Impact printer use electromechanical mechanism that causes
hammer or pin to strike against a ribbon and a paper to print
the text.
 Non Impact Printer, A printer that creates an image without
striking a ribbon against the paper.It does not use
electromechanical printing head to strike against ribbon and
paper.These type of printer use thermal, chemical, electrostatic,
laser beam or inkjet technology for printing the text.
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DOT MATRIX PRINTERS
 It use a matrix of small pins to create precise dots.
 In this character is printed by printing the selected no of
dots from a matrix of dot. The formation of a character has
been shown 5 dot rows and 7 dot columns. This pattern is
called 5*7 dot matrix. In this character is printed by
printing the selected no of dots from a matrix of dot. The
formation of a character has been shown 5 dot rows and 7
dot columns. This pattern is called 5*7 dot matrix.
 Such printers would have either 9 or 24 pins on the print
head. Print head is that part of the printer that creates the
printed image.
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INKJET PRINTER
 It is a type of non impact printer. It is a printer that creates
an image by spraying tiny droplets of ink from the
printhead.
 In ink-jet printer, whenever we want to print the image the
nozzel spread the ink, so there is a permanent remark on
the paper. Suppose there is a 5 pin then it spread the ink
up to 5 pixels. But it can approximately print up to 16 to
32 pixel at a time.
 In inkjet printer the ink is stored in a cartridge.A colour
inkjet printer cosist of four cartridge one each for blue,
green, cyan, magenta and black.
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LASER PRINTER
 Laser printer are page printer. They make use of laser
beam to produce an image of the page containing text
/graphics on a photo sensitive drum.
 A laser printer uses a rotating disc to reflect laser beam
onto a photosensitive drum, where the image of the page
is converted in to an electrostatic charge.
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PLOTTER
 Plotter used to produce good quality drawings and
graphs.
 Drum plotter: It contain along cylinder and a pen
carriage. The paper is placed over the drum. The drum
rotates back and forth. The pen moves horizontally along
the surfacei.e either left to right or right to left.
 Flat-Bed Plotter: It uses horizontal flat surface on which
paper is fixed and the pen moves along both the axes i.e. x
axis and y axis.
 Inkjet Plotter: These plotter uses inkjet in place of ink
pens.
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VDU(VIDEO TERMINAL)
 A computer display is a device that can display signals
generated by a computer as images on a screen.
Quality factors used in monitor are:
 Pixels: It is the smallest unit of monitor which is displayed
without disturbing the other point .While designning the pixels,
some distance between the pixels must be there in the
horizontal as well as in vertical directin also.
 Aspect Ratio: It is the ratio of the pixels in the horizontal as
well as in vertical direction also.
 Resolution: No of pixels in a per unit area.
 Refreshing Rate: The rate by which the pixels glow again
Refreshing Rate = 1/Refreshing Time
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VDU IS CATEGORIZED INTO
 CRT
 Non CRT
CRT Display
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Non CRT Display
 LCD
 LED
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SPEAKER
 Speaker is one of the output devices which is mainly used
for entertainment, video conferencing etc.Computer
speakers, or multimedia speakers, are external speakers
and are usually equipped with a male-end stereo jack plug.
 The sound capability of the computer system does not
work unless and unti there is a sound card. Speaker
recieves the data from the sound card in the form of
electric signal and then convert it in to the sound format
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•First Generation
1946-1955
•Second Generation
1956-1964
•Third Generation 1964-1971
•Fourth Generation
1971-Present
•Fifth Generation Present-Future
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First Generation Computers
 The era of the first generation computers began in 1946
because that was the year when people consciously set out
to build stored program computers. In 1946 there was no
'best' way of storing instructions and data in a computer
memory. There were four competing technologies for
providing computer memory:
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Electrostatic storage tubes,
Acoustic delay lines (mercury or nickel),
Magnetic drums (and disks),
Magnetic core storage.
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Some computers of these generations are given below
:
 ENIAC
 EDVAC
 EDSAC
 UNIVAC
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Characteristics of First Generation Computers
 Used vaccum tubes
 Not reliable
 Big and clumsy computers
 Electric consumption is very high
 This type of computers generate too much heat,
therefore air conditioners are required.
 Batch processing
 Slow Input/Output operations.
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Second Generation Computers
 Transistor takes place of vaccum tubes.
 Faster than first generation.
 Assembly language is used instead of machine
language.
 Generate less heat
 Smaller in size
 Magnetic tapes and disks are used.
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Third Generation Computers
 Transistors is replaced integrated circuits
 Increases speed as well as reliability.
 Uses multiprogramming operating system
 Lower power consumption
 Magnetic disk can be used as a secondary storage.
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Fourth Generation Computers
 Very large scale and ultra large scale integrated
circuits has been developed.
 Computers now becomes portable.
 Semiconductor can be used as primary storage.
 Database Management system can be used
 Distributed data processing.
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Fifth Generation Computers
 Fifth generations computers are only in the minds of advance
research scientists and being tested out in the laboratories. These
computers will be under Artificial Intelligence (AI), They will be
able to take commands in a audio visual way and carry out
instructions. These computers will perform many of the operations,
which require low human intelligence.
 Parallel Processing is coming and showing the possibility that the
power of many CPU's can be used side by side, and computers will
be more powerful than those under central processing. Advances in
Super Conductor technology will greatly improve the speed of
information traffic. Future looks bright for the computers.
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Description Of a Processor
• The processing unit in a computer interprets
instructions given in a program and carries out the
instructions.
• Processors are designed to interpret a specified number
of instruction codes. Each instruction code is string of
binary digits.
• All processors have input/output instructions,
arithmetic instructions, logic instructions, branch
instructions and instructions to manipulate characters.
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• In this section we will describe the processor of a
hypothetical computer which we will call HYPCOM. The
processor of HYPCOM has an accumulator register (ACC).
The other registers are an instruction register (IR) and a
program counter register (PC).
• The instruction register is used to temporarily store the
instruction being executed. It consist of two parts :
1) An operation code part
2) Address part
• The PC register stores the address of the next instruction to
be executed.
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The other specifications of HYPCOM are :
1) It has a 4K word addressable memory.
2) A word of HYPCOM is 16 bits long.
3) A word of HYPCOM stores either an instruction or data to be processed.
4) It has 15 operation codes.
5) The instructions are single address instructions. Four bits are needed to represent
15 operation codes. Twelve bits are needed to address a 4K memory
An instruction is thus 16 bits long.
6) It has an input unit which is used to feed both instructions and data.
A 16 bit word is read via the input and stored in memory when a READ operation
code is executed by the processor.
7) It has a printer as its output unit which is used to output a 16 bit word from the
memory when a PRINT operation code is executed by the processor.
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CLA:
Clear accumulator and place contents of specified memory address in it.
ADD
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ADD to the accumulator contents of specified address.
SUB
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Subtract from the accumulator contents of specified address
MUL
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Multiply contents of accumulator by contents of specified address.
DIV
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Divide the contents of accumulator by the contents of specified address
and leave integer quotient in accumulator.
STO
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Store contents of accumulator in the specified address in memory.
JMP
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Take next instruction from address 653 of memory.
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JNE
 Take next instruction from address 446 if ACC<0 else next instruction
from address given in PC.
JZE
 Take next instruction from the address 648 if ACC=0 else next
instruction
from the address given in PC.
READ
 Input into specified address in memory data read from input unit.
PRINT
 Print data retrieved from the specified address in the memory.
SHR
 Shift contents of ACC right by 8 bits.
COM
 Complements contents of ACC.
EOR
 Match each bit of ACC with each bit of contents of specified address.
HLT
 Halt computation
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COMPUTER LANGUAGE
 Computer programming languages are developed
with the primary objective of facilitating a large no. of
people to use computers without the need to know in
detail the internal structure of computer.
 Languages are matched to the type of operations to be
performed in algorithms for various application.
 Languages are also designed to be machineindependent.
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A. Machine Language
Machine language is a system of instructions and data
which is directly understandable by a computer's
central processing unit. In this instructions are
patterns of bits. Depending on the processing
architecture, a given instruction may specify:
 Particular registers for arithmetic, addressing, or
control functions
 Particular memory locations or offsets
 Particular addressing modes used to interpret the
operands
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Advantages Of machine Language
The machine easily understands these languages.
Processing is faster.
Limitations Of Machine Language
It is machine dependent; it is different from one computer
to another.
 All the instructions are to be given into binary digits,
therefore it is very difficult to program.
 It is difficult to rectify a program written in machine
language.
 It is very time consuming and tedious task to write a
program in machine language.
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B. Assembly Language
 Writing the programs in machine language is a
very tedious and boring job. To solve this problem,
assembly languages is developed which makes use
of alphanumeric symbols for writing the set of
instruction instead of 0 and 1.
 A program written in assembly language consists
of a series of instructions in symbolic code i.e.
mnemonics that correspond to a stream of
executable instructions, when translated by an
assembler, that can be loaded into memory and
executed.
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Advantages Of Assembly Language
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Easy to understand because of mnemonic code.
Easy to detect and correct error.
Eassily modified
It saves time and reduce complexity than machine language
program.
 The computation time of assembly anguage program is
less.
Limitations
 The assembly language is machine oriented. This means
that program must have the detailed knowledge of the
structure of the computer.
 Assembly language program contains more instruction as
compared to high-level languages
 Writing assembly language programs is difficult and time
consuming..
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C. High Level Language
Advantages Of High Level Language
 It is a machine independent language.
 They are easier to learn and understand.
 Program written in this language are portable and easier to
maintain.
 In this program can be easily written because natural
language English is used.
Limitations
 The high level language program take more time to run.
 Computer are unable to understand instruction given in
high level language.
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OPERATING SYSTEM
An operating system is a program that control
the execution of application programs and acts
as an interface between the user of a computer
and the computer hardware.
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OPERATING SYSTEM
The structure of OS consists of 4 layers:
1. Hardware
Hardware consists of CPU, Main memory, I/O
Devices, etc,
2. Software (Operating System)
Software includes process management
routines, memory management routines, I/O
control routines, file management routines.
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3. System programs
This layer consists of compilers, Assemblers,
linker etc.
4. Application programs
This is dependent on users need. Ex. Railway
reservation system, Bank database
management etc.,
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Services provided by OS
 Program development
 Program execution
 Access to I/O devices
 Controlled access to files
 System access
 Error detection and responses
 Accounting
 Resource allocation
 Communication
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Functions of Operating Systems
 Provide a user interface
 Run programs
 Manage hardware devices
 Organized file storage
• In a desktop computer, these resources include
such things as the processor ,memory and disk
space
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 It provides a stable, consistent way for applications to
deal with the hardware without having to know all the
details of the hardware.
 The OS also determines how you see information and
perform tasks. Some operating systems utilize a
graphical user interface (GUI), which presents
information through pictures (icons, buttons, dialog
boxes, etc.) as well as words.
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 OS performs a variety of functions, including




determining what types of software you can install.
coordinating the applications running on the
computer at any given time
making sure that individual pieces of hardware, such
as printers, keyboards, and disk drives, all
communicate properly
allowing applications such as word processors, email
clients, and web browsers, to perform tasks on the
system
reporting errors.
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Core Process Of Operating system
 Process Management
 Memory Management
 File Management
 Device Management
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Process Management

The creation and deletion of both the user and
system processes.
The suspension and resumption of process
The provision of mechanism for process
synchronization
The provision of mechanism for dealock handling.
When a program is submitted to the CPU, it may be
one of the three states:







Running
Ready
Wait
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Memory Management

Keep track of which part of the memory are
currently being used and by whom.

Decide whichprocess is to be loaded in to the
memory when the memory space becomes
available.

Allocate and deallocate the memory space as
needed.
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File Management

The creation and deletion of file.

The creation and deletion of directories.

The mapping of file on to the secodary storage.

The backup files on stable storage media.
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Device Management

It should activate them, control them, issue
command to the device, handle errors etc.

It should also provide an interface between the
devices and the system, so that it becomes easy to
use this devices.

The operating system provide coordination between
all the peripheral devices, instead of they arev quite
different.
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Types of Operating Systems
Real-time operating system
 RTOS are used to control machinery, scientific
instruments and industrial systems.
 Real time systems which were originally used to
control autonomous systems such as satellites and
robots
 Very fast small OS
 Built into a device
 Respond quickly to user input
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Single user/Single tasking OS
 One user works on the system
 Performs one task at a time
 MS-DOS and Palm OS
 Take up little space on disk
 Run on inexpensive computers
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Single Tasking
 Operating System cannot be able to take control
back from the running process/task/application
 In case if a process call an I/O Instruction then
Processor must wait for I/O instruction to
complete before preceding
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 Example of Single User, Single Task
 The Palm OS for Palm handheld computers is a good
example of a modern single-user, single-task operating
system.
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Single user/Multitasking OS
 User performs many tasks at once
 Most common form of OS
 Windows XP and OS X
 Require expensive computers
 Tend to be complex
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Multitasking
 Operating System can take control back
from the running process and can give it to
other.
 When one job needs to wait for I/O, the
processor can switch to the other job
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Example of Single User, multi Tasking
 Microsoft's Windows and Apple's MacOSplatforms are
both examples of OS that will let a single user have
several programs in operation at the same time.
 For example, it's entirely possible for a Windows user
to be writing a note in a word processor while
downloading a file from the Internet while printing
the text of an e-mail message.
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Multi user/Multitasking OS
 Many users connect to one computer
 Each user has a unique session
 UNIX, Linux, and VMS
 Maintenance can be easy
 Requires a powerful computer
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Multi user/Multi tasking OS
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Examples of Multi-user
 Unix, VMS and mainframe operating systems, are
examples of multi-user operating systems.
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BATCH OS
 Some computer systems only did one thing at a time.
They had a list of instructions to carry out and these
would be carried out one after the other. This is called
a serial system. The mechanics of development and
preparation of programs in such environments are
quite slow.
 Batch operating system is one where programs and
data are collected together in a batch before processing
starts. A job is predefined sequence of commands,
programs and data that are combined into a single unit
called job
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 Figure below shows the memory layout for a simple batch
system.
 Memory is usually divided into two areas: Operating system
and user program area.
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Advantages of Batch System:
 1. Move much of the work of the operator to the
computer.
 2. Increased performance since it was possible for job
to start as soon as the previous job finished.
Disadvantages of Bach System:
 1. Turn around time can be large from user standpoint.
 2. Difficult to debug program.
 3.A job could enter an infinite loop.
 4.A job could corrupt the monitor, thus affecting
pending jobs.
 5.Due to lack of protection scheme, one batch job can
affect pending jobs.
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MULTIPROGRAMMING OS
 When two or more programs are in memory at the
same time, sharing the processor is referred to the
multiprogramming operating system.
 Multiprogramming assumes a single processor that is
being shared. It increases CPU utilization by
organizing jobs so that the CPU always has one to
execute.
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 Figure below shows the memory layout for a
multiprogramming system.
( Memory layout for a multiprogramming OS)
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Advantages
 1.High CPU utilization.
 2. It appears that many programs are allotted CPU
almost simultaneously.
Disadvantages
 1.CPU scheduling is required.
 2.To accommodate many jobs in memory, memory
management is required.
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DESKTOP OS
 During the late 1970, computers had faster CPU, thus
creating an even greater disparity between their rapid
processing speed and slower I/O access time
 Multiprogramming schemes to increase CPU use were
limited by the physical capacity of the main memory,
which was a limited resource and very expensive.
These system includes PC running MS window and the
Apple Macintosh.
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 MS-DOS is an example of a microcomputer operating
system.
 The most powerful microcomputers used by
commercial; educational, government enterprises.
Hardware cost for microcomputers are sufficiently low
that a single user (individuals) have sole use of a
computer. Networking capability has been integrated
into almost every system.
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TIME SHARING OS
 Time sharing system supports interactive users. Time
sharing is also called multitasking. It is logical
extension of multiprogramming.
 Time sharing system uses CPU scheduling and
multiprogramming to provide an economical
interactive system of two or more users.
 In time sharing, each user is given a time-slice for
executing his job in round-robin fashion. Job
continues until the time-slice ends.
 Time sharing systems are more complex than
multiprogramming operating system.
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MICROKERNEL OS
 A microkernel is very small core of OS that allow easy
portability of OS across different vendors computers.
 It is predicted that all future OS will be built around a
microkernel.
 The microkernel approach replaces the layered
approach of UNIX by a horizontal organization.
 Fig shows the organization of microkernel called
chorus developed in France.
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Chorus microkernel OS organization
Unix
Proce
ss
Unix
Procs
ee
Unix
Proces
s
Proce
ss
mgr
Disk
Drive
r
File
Mgr
Real time
executive
Inter process
communication
Memory
manager
User
Space
System
Space
Chorus
nucleus
Machine dependent supervisor
Fig. Chorus microkernel OS organization
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Unix OS
 Unix is multiuser,time sharing OS which was written
in 1973 by Ritchie and Thomson at Bell Telephone
Laboratories USA.
Features of UNIX OS: Unix is writen in C, a high level language.
 The interface provided to user is simple and powerful.
 The file system used by UNIX is hierarchical which
allows efficient implementation and easy
maintenance.
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 UNIX is multiuser,time sharing,multiprogramming
OS.
 UNIX supports scripting language called shell.
 UNIX can support any programming language that has
a compiler or an interpreter.
Fig shows the layers of UNIX OS
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H/W
For diagram refer book
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•In computer science,computer software is nothing but all
computer programs.
•To perform any task on computer, the programmer has to
write a set of instruction.
•This sequence of instruction given to the computer is
called a program.
•A set of program written for the computer is called
software.
•Software is a program that enables a computer to
perform a specific task, as opposed to the physical
components of the system.
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SOFTWARE
 Software may be classified into 2 types: Application software
 System software
application software :It is the set of programms necessary to carry out the
operation for the specified application.
System software:They are general programs written for the system
which provide the environment to facilitate the
writing of application software.
Ex. Assembler, Compiler, Loader, Linker etc.
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System Software
 System Control Software
 System Support Software
 System Development Software
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System Control Software:
 System Control programs control the execution of
programs, manage the storage and processing resources of
the computer, and perform other management and
monitoring functions. The most important of these
program is the operating system & DBMS(Data Base
Management System).
 Operating system: An operating system is a program that
acts as an intermediate between the user and computer
hardware.
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System Development Software :Language Processor
A Compiler
B Assembler
C Interpreter
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System Support Software :Utility Software
 Disk defragmenters/Disk management tools
 Virus scanners/Antivirus
 Compression
 File Management tools
 Encryption
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Current Storage Format
 CD’s
 Consist of pits and lands
stamped out in a spiral
pattern on the disc.
 A laser then reads the
pits and lands.
 The change from a pit to
a land or a land to a pit
indicates a one while no
change indicates a zero.
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Current Media Format Cont.
 CD-RW’s
 Consist of a metal phase
change alloy which
when heated can be to
change to reflectivity
 CD-R’s
 Consist of a dye that is
applied to the disc.
 When a writing laser is
shined it changes the
reflectivity.
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Current Media Format Cont.
 DVD’s
 Also contain pits and
lands.
 Are more highly
compact than a CD.
 Special laser is needed
to read them.
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Blu-ray Technology
 Name
 Derived from the blue-
violet laser used to read
and write data.
 Developed by the Bluray Disc Association
with more than 180
members.



Dell
Sony
LG
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Blu-ray Technology Cont.
 Data capacity
 Because Blu-ray uses a
blue laser(405
nanometers) instead of
a red laser(650
nanometers) this allows
the data tracks on the
disc to be very compact.
 This allows for more
than twice as small pits
as on a DVD.
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Blu-ray Technology Cont.
 Data Capacity Cont.
 Because of the greatly compact
data Blu-ray can hold almost 5
times more data than a single
layer DVD. Close to 25 GB!
 Just like a DVD Blu-ray can also
be recorded in Dual-Layer
format. This allows the disk to
hold up to 50 GB!!
 Because the polycarbonate layer
of the Blu-ray disc is so much
larger than a DVD because the
recording layer is so much
smaller it can have even more
than two layers.
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Blu-ray Technology Cont.
 Writing Data
 Blu-ray uses a
combination of two
lenses to greatly shrink
the laser to read the
data.
 This also allows for
higher data rate transfer
close to 36 mbps.

It could record 25 GB of
data in an hour an a half.
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HD DVD vs Blu-ray
 Both formats use blue lasers rather than red.
 Both have the same options for video and audio compression.
 Blu-ray offers significantly more storage space -- 50 GB on a dual-layer disc versus HDDVD's 30 GB.
 The DVD Forum, which creates DVD standards, has approved HD-DVD and has not
approved Blu-ray.
 HD-DVD is less expensive than Blu-ray.
 HD-DVDs can be produced on existing equipment, and Blu-ray discs can't.

 HD-DVD players are selling for $499 (Toshiba HD-A1) to $799 (HD-XA1), and Blu-ray
players are selling for around $1,000 (Samsung DB-P1000).
 HD-DVD players hit the market on April 18, 2006, two months before the first Blu-ray
player hit the U.S. market in June, 2006.
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HD DVD vs Blu-ray Cont.
 Current supporters of HD-DVD include Toshiba, NEC, Sanyo, and
Microsoft, in addition to New Line Cinema, Paramount, Universal, TimeWarner, and the official approval of the DVD Forum.
 Current supporters for Blu-Ray includes PC makers Apple,
Dell, Hewlett-Packard, and Sony, and electronics giants
Hitachi, LG, Mitsubishi Electric, Matsushita/Panasonic,
Pioneer, Philips, Samsung, Sharp, TDK, and Thomson. Add
to this the support by movie studios such as Columbia
TriStar, Sony Pictures and MGM (all three owned by Sony),
20th Century Fox, Lions Gate Entertainment, and Disney, as
well as video game makers Electronic Arts and Vivendi
Universal Games, and the bastion of support for Blu-Ray
looks formidable indeed
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The Hard Drive
 Hard drives are composed of individual disks or
platters
 The platters are made up of aluminum and coated with
a magnetic medium
 Two tiny read/write heads service each platter
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The Hard Drive
 The closer the read/write heads are to the platter, the
more densely the data can be packed on to the drive
 Hard drives use a tiny, heavily filtered aperture to
equalize the air pressure between the exterior and
interior of the hard drive
 Platters spin between 3500 and 10,000 rounds per
minute (RPM)
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Types of Hard Disk Drives
ATA is the current standard, it uses regular molex power connectors and IDE cables.
SATA is a newer product (also SATA2 is already in development) - it is faster than
ATA and uses different cables - much thinner and neater.
Also take into consideration the RPM of the drive, 5400 is a bit slow, 7200 is good,
10,000 is fast but can be quite noisy.
Servers generally use 10k rpm SCSI hard drives, but SCSI is unusual in home
computers.
Most motherboards only have IDE connections and so can only take ATA, you would
need a new motherboard for SATA hard drives.
The capacity that you need is simply dependant on how much you plan on saving to
your hard-drive. Usually from 40GB upwards
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Hard Drive
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Data Encoding
 Hard drives store data in tiny magnetic fields called fluxes
 The flux switches back and forth through a process called flux
reversal
 Hard drives read these flux reversals at a very high speed when
accessing or writing data
 Fluxes in one direction are read as 0 and the other direction as 1
Data Encoding
 Encoding methods used by hard drives are
 Run length limited (RLL)


Data is stored using “runs” that are unique patterns of ones and
zeroes
Can have runs of about seven fluxes
 Partial Response Maximum Likelihood (PRML)



Uses a powerful, intelligent circuitry to analyze each flux reversal
Can have runs of about 16 to 20 fluxes
Significantly increased capacity (up to 1 TB)
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Arm Movement in the Hard Drive
 The stepper motor technology and the voice coil
technology are used for moving the actuator arm
 Moves the arms in fixed increments or steps
 Only seen in floppies today
 The voice coil technology uses a permanent magnet
surrounding the coil on the actuator arm to move the
arm
 Automatically parks drive over non-data area when
power removed
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Geometry
 Geometry is used to determine the location of the data
on the hard drive
 CHS (cylinders, heads, sectors)
 Used to be critical to know geometry
 Had to enter into CMOS manually
 Today, geometry stored on hard drive
 BIOS can query hard drive for geometry data
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Heads
 Number of read/write heads used by the drive to store data
 Two heads per platter
(top and bottom)
 Most hard drives have an
extra head or two for their
own usage, so the number
may not be even
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Basic components of a hard drive
 Disk platters
 Read/write heads
 Head actuator mechanisms
 Spindle motor
 Logic board
 Cables & connectors
 Configuration items (such as jumpers & switches)
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Hard Disk Platters
 Hard disks have been a number of different form
factors over the years
 3 1/2 inch drives are the most popular for desktop &
some portables
 Max number of platters in a 3 1/2 inch drive is 11
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Hard Disk Platters
 No matter what type of platter is used, the platters are
covered with a thin layer of magnetically retentive
substance (called the medium) on which magnetic
information is stored.
 Oxide media
 Thin-film media
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Read/Write Heads
 A hard disk has one read/write head for each side of
the platter
 The heads are connected on a single movement
mechanism
 They move in unison
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Head Actuator Mechanism
 A drive using a stepper motor is much less reliable
than one using a voice coil
 Floppy drives use a stepper motor to position their
heads
 Accuracy of the stepper is suited to a floppy drive,
because track densities usually lower
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Spindle motor
 Motor that spins the platters
 Connected directly to the drive
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Logic Boards
 Mounted on the hard drive
 Contain electronics that control the drive’s spindle &
head actuator systems & present the data to the
controller
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Cables & Connectors
 Sever connectors for interfacing to the computer,
receiving power & sometimes grounding to the system
chassis
 Three types
 Interface connectors
 Power connectors
 Option ground connector (green wire)
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Speed of the Drive
 Average Seek time
 Measured in milliseconds - average amount of time it
takes to move the heads from one cylinder to another
cylinder a random distance
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