Chapter III
Understanding computer hardware
1- Introduction about computer evolution
a. Human being started the chase for computation help since the dawn of
civilization. We witness the chase continue presently at a faster pace and sure
its trend is to persist in the future at much faster pace because of the
progressive emerging needs for digital information processing in the human
society and the global environment.
b. The earliest known computing tool is the Abacus (figur3-1 and 3-2), also called
“counting frame” that consists of beads sliding on metal wires fit into a
rectangular wood or bamboo frame.
Figure 3-1: Abacus sample (courtesy MS clip art gallery)
Figure 3-2: Abacus sample (courtesy MS clip art gallery)
i. The abacus was used since 3000 BC (long before human knew the
numeral systems) by the Sumerian, the Egyptians, the Phoenicians, the
Persians, the Greeks and the Romans and most ancient civilizations and
it is still used by merchants and clerks in some countries in Asia, Africa,
the Middle East.
ii. In 1985 Robert Good Jr. explained in his article published in the “Journal of
computers” an approach in Mathematics and science teaching using a binary
Abacus. Normal Abaci were used in schools around the world to teach numeral
systems and mathematical operations.
iii. In the early 1980s Tim Cranmer developed an abacus (known now as Cranmer
abacus) for the blind and vision impaired people after having developed the
modern braille code.
c. In 1645, Blaise Pascal, famous French mathematician and philosopher, invented a
machine he called Pascaline which is a mechanical calculator, but that machine was
subject to a lot of problems.
d. Digital electronic computers:
i. The first digital electronic computer was introduced in 1937 by J. Atanasoff and
C. Berry Known as ABC (Atanasoff-Berry-Computer).
ii. In 1943, Dr. J Mauchly and J Eckert Jr. and their team completed their 30 metric
tons ENIAC (Electronic Numerical Integrator and Computer) with big dimensions
30x50 feet. That computer with its 18000 vacuum tubes needed more than 150
kilowatts of power.
2- Digital electronic device/computer:
a. Modern industry uses a lot of digital electronic devices to perform automatic functions
in many products such as:
i. Automobile industry uses a computer like device to control many of the car
performances.
ii. Appliances: cooler, Freezer, washer/dryer, dishwasher, etc…
iii. Construction business use electronic devices in many building activities.
iv. Hospital machinery
v. Smart weapon and military industry
vi. GPS and autopilot devices
vii. Most modern devices and equipment used in all human and life activity enjoy
the enhanced high performance digital electronic devices.
b. A modern computer is a digital electronic device used by people to help them make
correct decisions and efficiently tackle the heavy load of daily data and information
generated by:
i. Their social life and living environment
ii. Their business environment
iii. Their education and literacy
iv. Their entertainment and knowledge needs
v. The natural global variables.
3- Computer components:
a. Computer industry evolve around three computer components
i. Computer Hardware
ii. Computer software
iii. Computer malware
b. Computer hardware comprises structural computer components and peripherals that
also comprise all type of devices that complement the computer system and enhance its
operational performance.
c. The ultimate goal set for a computer in the early steps was to have a device that can
compute numbers and help in solving mathematical problems.
d. After the adaptation of the binary numeration system and the implementation of the
binary digital data representation, the computer goals were set much higher as it
became possible to simulate human functions enhanced with super speed, super
precision and super power.
e. To be able to simulate human activity a computer must be able to:
i. Accept all types of data input
ii. Process data into information
iii. Produce all needed types of output
iv. Provide high flexibility and perfect accuracy.
v. Store information and be ready to retrieve it and use it when needed.
vi. Communicate easily with users and other computers.
f. To fit these obligations computer hardware components are composed of the following
hardware devices: (Figure 3-3)
i. Input devices:
1. Mouse and pointing devices
2. Touch screen and stylus input
3. Text input: keyboard, scanners, text recognition
4. Multimedia input: Microphone, digital camera and video camera.
5. Sensors with diverse input roles.
ii. Processing devices
1. Processor also called microprocessor.
2. Advanced technology to enhance its processing speed
iii. Storage devices:
1. Magnetic storage
2. Optical storage
3. Solid state storage
iv. Output devices
1. Monitor
2. Printers
3. Laser
4. Audio
5. video
6. Various automated tools in various business activities
v. Communication devices
1. Network interface card
2. Network Modem
3. Internet modem
4. Various slot to connect various devices
vi. Housing and local communication and synchronization devices
1. The motherboard
2. The bus
3. The local wiring
4. The ports
5. The slots
Processor
CU
ALU
ROM
BIOS
Other computer
Input
keyboard
Memory
Output
RAM
Monitor
CMOS
Date/tim
e
Storage
Other computer
Hard disk
Figure 3-3: Computer components
Input
1- Input is designed to enter instructions and/or data necessary for the computer system to
perform. It is used as interface with the computer.
2- Input affects all operations a computer needs to perform safely and accurately so it can provide
the necessary information requested by businesses and individuals.
3- To highlight the importance and sensitivity of input, computer people use the slogan: Garbage in
Garbage out (GIGO) that necessitates rigorous verification of input safety and accuracy.
4- It is very important that business employees, as users of the business computer information
system, be knowledgeable of input environment so they can determine what input technology
and accessories they need:
a. To feed their computer systems with data.
b. To accommodate their executives, shareholders or partners, customers and suppliers
c. To provide necessary tools for all outside agents and businesses providing work or help
to their company.
Input technology
Diverse hardware technologies contribute in covering the huge array of input needs. These technologies
can be classified as:
1- Keyboard: The oldest known data entry typewriter style device:
a. The classical keyboard consists of a set of 104 buttons or keys fit in a rectangular frame.
i. A key may represent The ASCII binary codes of two or more characters and
symbols in many languages.
ii. A function or a functional operator
iii. A number or mathematical operator.
b. The most popular English keyboard is the QWERTY key board that is called by this name
because the arrangement of the 1st six letters from left to right form the word QWERTY.
c. The second is DVORAK
d. The newest technology is the Colemak keyboard that places the most frequently used
letters on a home row corresponding to the strongest fingers in keyboarding. Compared
to the previous technologies Colemak enjoys the following strengths:
i. Faster typing ratio
ii. Multilingual: It accommodates more than 40 different languages
iii. Easy transition from QWERTY and DVORAK
iv. Ergonomic: designed to have fewer finger jumping from one row to another
v. Available for Android, iPhone, iPad, Google play, etc…
Figure 3-4: Colemak keyboard layout (courtesy Colemak.com)
e. AZERTY is a 104 keys keyboard used in France and other non-English speaking European
countries where the A and Z swipe places with Q and W and the place of all other
characters remain unchanged.
Figure 3-5: AZERTY keyboard layout (courtesy Wikipedia)
f.
Chorded keyboard layout sample: Figure 3-6 (courtesy Kudzu world)
Consists of few keys and the data entry is like you play on piano chords (enter
characters by pressing several keys together)
i. Each key represents a bit
ii. 8 keys are enough to enter 256 different combinations
iii. Chording few keys that fit in a small device would be enough to operate devices
Like in smart phones, iPhone, iPad and Android
iv. Requires more practice and advanced skills.
g. Optical keyboard technology:
i. Uses photo sensors and light emitting parts.
ii. Sensors and light parts are mounted on printed circuit boards (PCBs)
iii. The pressed key blocks the light and activates the code of the character.
2- Pointing technology: consists of 2 categories:
a. Motion detection:
i. A clickable mouse slid over a smooth surface moves a pointer or cursor and
position it over a clickable target.
ii. Rotating a trackball into a socket activates sensors fixed in the socket and
movestouch the cursor on the screen. Commonly used in CAD stations.
iii. Joystick: used in games apply pressure while moving a stick.
Figure 3-7 Motion detection mouse (courtesy Microsoft clip art gallery)
b. Touch detection:
i. Touchpad: uses electrodes layers to detect finger contact and motion so you can
scroll by moving your finger while touching the pad and click by tapping on any
point of the pad.
ii. Graphics tablet: also called digitizing tablet is similar to the touchpad but it is
activated using an electronic or magnetic head stylus to activate the cursor
1. Used in tablet laptops.
2. Also used to digitize signatures and hand written things in banks, stores
and other employment and government places.
iii. Touch screen technology: based on highly sensitive electronic device embedded
into the screen of a monitor.
1. The finger or stylus touch results in a change of the electric current and
send to the processor the code of the affected area.
2. This technology is highly used in most modern devices like smartphones,
iPad and Android, etc…
3. iPad and Android allow users to get a keyboard on the screen pad and
type exactly like using a laptop or any PC or MAC.
c. Gaming technology: pressured computer industry to advance forward several devices
needed to control moving objects and play the game. Like the light pen, the light gun,
the steering wheel and paddle for automobile simulators and the yoke for aircraft
simulator also to highlight:
i. Game controller (remote control) and gamepad
ii. Wii remote controller is motion detection remote created by Nintendo for its
video games. Wii use Bluetooth to connect with game devices.
3- Multimedia input technology: digitize pictures audio and video and provide it to the processor.
a. Picture (image):
i. Digital camera captures live pictures, digitize them and store them on a flash
card memory to be entered to the computer later.
ii. Scanner converts printed pictures and documents into bitmap files we can
consider many types of scanners that use different technology of image sensors
to reproduce the image of the document.
1. Flatbed scanner: figure 3-8 takes printed documents and images that
are placed on its bed and digitizes all their pixels.
Figure 3-8 (flatbed scanner(courtesy Microsoft)
2. WAND scanner: called after the ancient Pharaohs magic stick. Wand
scanner scans by moving over the surface of the document.
Figure 3-9: wand scanner
3. 3D scanners: used in engineering projects for industrial design.
4. Drum scanners use photomultipliers tube as image sensor
5. DNA scanners use charge coupled device (CCD) or photomultipliers to
detect microscopic DNA arrays.
Figure 3-10: DNA micro-array scanner (curtsey U-strasbg- Fr)
b. Video:
i. Digital camcorder captures and digitizes film and clip footage so they can be
processed and used by computer systems.
ii. Webcam linked to the computer shoots and converts live clip footage instantly
and feed them into the system so they can be used in video telephony and
teleconferencing and live news reporting
iii. Traffic camera is the base of many traffic applications (TIS: Traffic Intelligent
System)
iv. The digital camera embedded in the smart phone is very convenient to shoot
and email digital pictures and video clips while they are happening contributing
to the greatness of this convergence device.
c. Audio:
i. Microphone captures voice, sound and music and transfers them to an audio
device where they are digitized and used in the context of their happening.
ii. MIDI (Musical Instrument Digital Interface) captures notes and encodes them as
digital messages into the computer processor and synchronizes the rhythm of
multiple devices.
iii. MIDI piano-like keyboard doesn’t produce sounds. This keyboard send
information to the computer who reproduces an array of voices or samples
iv. The MIDI protocol controls all components and parameters of the sounds of an
instrument sample.
v. Perhaps the most important role of MIDI protocol is to ensure that many music
devices communicate with each other and with the computer system.
d. Bare voice input recognition
i. Computer can be taught to recognize spoken words.
ii. Words must correspond to vocabulary of its dictionary
iii. Software application helps complete the performance.
4- Medical input technology: Of course there are too many other areas where input has specific
importance. Here we will consider the health concerns.
a. MRI (Magnetic resonance imaging) use huge magnet surrounding a bed where the body
is subject to resonance produced by short electromagnetic field. The resonance causes
protons in the body water to align and then to rest. The measurement of these protons
gives clear panorama of the inspected region and precisely shows abnormal aspects.
Figure 3-11: MRI scanner
(courtesy mritechniciansite)
b. Computed tomography (CT) inputs many sectional X-rays for any penetrating wave
processed by the computer to create high precision tomograms for the inspected body.
Figure 3-12: CT scan (courtesy UCLAendocrinesurgery)
5-
6-
78-
i. CT scanning is a very popular technology because of the high quality of its 3D
pictures
ii. High number of tomograms produces ultra-high volume files that may be in the
order of several gigabytes of data for a CT scan session.
iii. Best known technology for the diagnosis of MS (Multiple Sclerosis) illness. In the
brain cells.
c. Industrial CT scanning use sectional X-rays as input used by the computer to create
three-dimensional designs for products and components.
d. Ultrasonography: use frequencies that are not audible as input (2 to 18 MHz) the
computer processes the waves and their influence on the body and produces scans that
are easily interpreted by specialists and handily viewed by people. An example is the
pregnancy sonogram.
e. Tiny digital camera introduced into human or animal veins and organs input pictures
processed by computers to locate obstructions or tumors or lesions etc…
Network and Internet input
a. Using indirect input forms designed to collect needed data for processing
b. Using several direct input technologies made available by several internet services:
Example the virtual keyboards and the scripts.
Internal input:
a. Information from files and folders on the hard disk.
b. Information from files saved on several storage media.
Paper input technology: use perforation or marks like the barcode tag attached to all
merchandise items available in stores.
Input technologies that feed computer system with data to produce information highlights the
importance of business employees to be literate, knowledgeable and vigilant so they can
contribute in designing the needed tools for their company.
Processing
Computer processing comprises steps performed by the processor to get information out of data input
and program instructions and deliver it by means of output.
Processing components are all located in the computer motherboard which represents the main circuit
board of the computer and provides housing for:
Figure 3-13 Motherboard courtesy Microsoft
art Gallery
-
All computer components.
The complementary electronic elements
The wiring that provides the internal link between them and the external link with the outside
The slots and expansion slots to fit different components
The ports that serve as interfaces with other computers and devices.
Computer processor
Central processing unit (CPU)
Figure 3-14: computer
processor chip courtesy
Microsoft art Gallery
The computer processor or central processing unit is a thumb-nail size chip or integrated circuit that
comprises 100 million to few billions of transistors and wiring that link them with the outside. It is
considered as the brain of the computer.
To fulfill its mission the processor has the necessary components as follows: (figure 3-3)
1- The control unit CU that performs the readiness, supervision and control roles
2- The arithmetic and logic unit ALU completes the necessary computing under the supervision of
the control unit.
Figure 3-15
Computer clock as the
human heart.(courtesy
Microsoft gallery
3- The computer clock:
a. Processing speed is the most important characteristic of the processor. It is determined
by the processor clock and defined as the number of machine cycle instructions a
processor can perform in one second.
b. In electronics, the number of cycles per second is defined as the frequency of the signal.
That’s why the processor speed (as the number of cycles per second) is like the signal
frequency measured in Hertz, kilohertz, megahertz, gigahertz and so forth.
c. The clock of the computer can be compared to the heart in the human body.
i. The heart synchronizes the blood circulation cycle in the body.
ii. During each pulse of the heart a blood circulation cycle is completed.
iii. Similarly, during each tick of the computer clock, at least one machine cycle
should be completed.
iv. For example: One GHz processor can process up to one billion machine cycles
per second.
v. We will go over many technologies that enable the processor to complete
several machine cycles during each clock tick!
d. Machine cycle comprises 4 steps that are, in the order: Fetch, decode, execute and
store which in turn can be divided into two operational steps:
i. The instruction operational step: Fetch and decode.
ii. The execution operational step: Execute and store.
4- The word size (also: word width or word length) refers to the processing and addressing unit (it
is the number of bytes (or bits) that are processed by the instruction set as one unit).
5- Modern computers have word size of 32 bits (4 bytes) or 64 bits (8 bytes). While some modern
electronic devices have word size of 8, 9, 16, 24, etc…
6- The word size affects the software used in the computer.
Processor speed technology
Because of the importance of processing speed computer industry is always trying to enhance speed of
computer processing using many technologies that will be explained below:
1- Pipelining technology:
a. Normal processing without pipelining requires the processor to finish processing a cycle
completely before starting another cycle.
Figure 3-16: regular processing of cycles
Instruction1
Instruction2
Instruction3
Fetch – Decode – execute – store – fetch – decode – execute – store – fetch …
b. With pipelining the processor will be capable to process several machine cycles
simultaneously.
Figure 3-17: Pipelining processing of cycles
Instruction1: Fetch – decode – execute – store
Instruction2:
Instruction3:
Fetch – decode – execute – store
fetch – decode – execute – store
2- Co-processing technology:
a. This technology assigns some sophisticated time consuming processing to specific
processors that help the main processor to tackle these specific tasks.
Figure 3-17: Floating point addition (consists of representing the added
numbers with same exponent before proceeding with the addition).
54321.1234 + 555.444 = (5.43211234 × 10^4) + (0.05554440 × 10^4)
= (5.43211234 + 0.0555444) × 10^4
= 5.487665674 × 10^4
= 54876.65674
b. Floating point mathematics processor achieves lengthy floating point calculations that
are very frequent in scientific and complex algorithms.
c. GPU (graphics processing unit) is a co-processor that, working together with the main
processor, accelerates the processing of multimedia and scientific applications.
Example: NVIDIA graphics processor.
Figure 3-18
3 processors linked in
parallel
Input software
3- Parallel processing technology:
Processor 1
Processor 2
Software for
results
Processor 3
a. Parallel processing consists of using a set of processor chips connected together in
parallel and designed to team up in tackling processing tasks.
b. Software is needed to divide the processing assignments equally between the
processors at the input and reconstruct the results at the output.
c. Supercomputers in general use this technology to reach ultra-high processing speed
they are built to achieve.
4- Multi-core technology:
a. While parallel processing technology use only one processor on each chip, multi-core
technology consists of putting two or more processors on one chip where they form one
integrated circuit and they time share its electronic components.
b. Intel launched the first core-2 duo in 2006 and the quad-core i7 in 2008 with 4
processors on the same chip i7.
c. In 2010 SUN/ORACLE launched the SPARC T3 processor that has 16 processors on one
chip that is a thumbnail size.
d. In 2012 AMD launched an 8-core with eight processors on the same chip.
5- Supercomputers use a combined technology of thousands of multicore processors grouped in
parallel to form an ultra-powerful ultra-fast processor
6- Initial speed factors- Processor clock:
a. Whether its technology is single core or multicore or parallel or combined, the speed or
power of any processor is determined by the frequency of its clock which is measured in
hertz (cycle per second).
b. 1 KHz= 1000 Hz, 1 MHz = 1000 KHz, 1 GHz= 1000 MHz, etc…
c. Processor clock of most laptop on the market is between 2 and 3 GHz which means that
the clock ticks 2 to 3 billion ticks per second and therefore they process as much
instructions.
Output
Computer output is information or action people and businesses want to get out of a computer as a
result of processing input data and information.
An output device is a computer component or device linked to a computer that is capable to:
1- Convey processed information to the user.
2- Complete an action required by the user.
Employees of each department of a company should be able to define their output needs and
coordinate with IT people to have these needs satisfied to the best possible.
Output needs may be classified as follow:
Printed output
1- Business requests for printed (hard copy) documents need different categories of printers to
fulfill them and they may be divided into 3 categories:
a. Normal print-out documents: reports, letters, notes, etc… An example is when the
customer service department asks for letters to be sent to clients or suppliers or
agencies.
b. Special documents: paychecks, cards, etc…
c. Pictures, brochure, fliers, banners and other colored forms and booklets.
2- A printer is a peripheral device that produces permanent readable hard copy designed to
satisfy the needs outlined above.
3- Modern printing technology produces four types of printers:
a. The dot-matrix printer: this technology uses solenoids (tiny magnets), a ribbon and a
guide plate.
i. Also called impact printer because it prints by impact of the print head or
pin driven forward by a tiny magnet.
ii. Prints one line at a time.
iii. Log life machine. They were very slowly.
b. The inkjet printer: The most commonly used printer technology that is based on
propelling ink particles onto the paper. Two ink technologies are used:
i. Continuous: uses high pressure pump and a microscopic nozzle that creates
a continuous stream of ink particles.
ii. Drop on demand: Canon, Hewlett- Packard and Lexmark use thermal inkjet
process also called bubble jet (Canon trade name)
iii. Another DOD technology used in Epson and Brother industries uses
software to create and direct ink bubbles in cartridge chambers.
c. The laser jet printer: This technology uses laser beam, dry ink (toner) and a rotating
drum coated with selenium. It works as follow:
i. The laser beam projects the image of the page on the drum
ii. Selenium photoconductors allow the charge to leak and particles of the
toner to be spread depending on the light density.
iii. The heated drum prints the image (documents and photos) by direct
contact that fuses the toner to the paper.
iv. Much faster and better quality than inkjet and dot-matrix printers
d. The LED printer (invented by Casio): similar to the laser printer but instead of the
laser beam the LED technology uses light-emitting diodes in the print-heads.
Compared to the laser printer the LED printer is:
i. More reliable and more efficient because they have less moving parts and
less mechanical wear,
ii. Faster
iii. Less expensive
4- Audio output: Beyond using speakers, headphones and ear buds to hear regular audio,
what’s interesting about computer audio may be included in the following properties:
a. You have an endless source of music stored on your computer or available and easy
to download in many online sites as Rhapsody for example.
b. You can play and hear the music in all the rooms of your house or your office and
you can even access them from all the rooms.
c. You can create playlists that suit occasions and events and easily chose and change
what you want to hear.
d. You can improve the quality of your audio by connecting your computer to a good
audio system.
5- Video output: video components work together to show the processed frame rate of
images on the monitor of computers or televisions. 2 scanning technologies and four display
technologies are used:
a. Scanning technologies
i. Interlacing technology: is the older technology and consists of sending the
signal in 2 steps or intervals: One half of the image vertical or horizontal
lines are sent first then the remaining half is sent later. This technology is
used in most SD televisions and monitors, however it is not used in LCD
(liquid crystal display) technology, gas plasma technology, or DLP ( )
technology.
ii. Progressive technology: The entire frame signals are sent simultaneously.
This scanning technology is most used by high definition television and
game monitors because of the easier way to compress and decompress
video.
b. Display technologies
i. CRT (Cathode Ray Tube) technology: based on the old vacuum tube
technology and 3 back guns that send red, green and blue electrons to
activate the color on a phosphoric screen. Because of the weight and
volume required to accommodate the monitor and the excessive power
consumption and generated heat, this technology was superseded by other
Figure 3-19: CRT (cathode ray tube)
Monitor courtesy Microsoft
modern technologies.
ii. LCD (liquid crystal display): This technology uses a natural liquid that have
the properties of any available liquid but its particles or molecules can be
oriented and polarized like those of crystal. Liquid crystal can be found in
Figure 3:20 LCD (Liquid
Crystal Display) courtesy
Microsoft Gallery
proteins and living cells.
1. Pros:
a. Low power needs.
b. Can be tailored to any size: small or large
c. Excellent quality resolution
d. Very compact and light weight.
2. Cons:
a. Highly influenced by temperature and light
b. Viewing angle is very limited
c. Dead pixels resulting of extensive use lower the image
quality.
d. Very heavy and big volume: Prohibitive in lrge and wide
displays.
iii. Gas plasma display: This technology uses a layer of ionized gas particles
similar to that of florescent lamps (vacuum bulbs) as a flat panel comprised
between two layers of glass.
1. Pros:
a. Excellent color due to very high contrast ratio: (10,000 : 1)
b. Very fast activation response
c. Good viewing angle
d. Highly scalable (up to 150”: world largest screen)
e.
2. Cons:
a. Large size screen (42 inches and over) required for good
quality because of the large pixel pitch needed.
b. Glass screen used in this technology may results often in
glare and reflections.
c. Heavier than LCD because of the glass weight.
d. Extended use produce deteriorated pixels that lower the
quality of gas plasma display earlier than that of LCD and
LED and even CRT.
e. Consume more power than LCD
iv. LED (Light Emitting Diodes) display: This technology is based on a cluster of
red green and blue diodes working together to produce the right color of
each pixel. When the emissive layer used in the diode is a film of organic
compound LED becomes OLED (Organic Light-Emitting Diode)..
1. Pros:
a. Lighter weight than all other displays
b. Very short image response time
c. Excellent color because no back light is used.
d. Wide viewing angle
e. Excellent contrast (more than 1000,000 to 1)
f. Because of its light weight, high quality and adaptability to
any display size this display technology is used in small
displays and advertisement and traffic displays
2. Cons:
a. Blue deteriorate faster than other color causing bad image
quality with extensive use
b. The organic material can be damaged from water and
vapor.
c. Long time exposure to sun light damages the quality of the
display.
d. Cost of production is higher than other displays
c. Display resolution:
i. All types of display are designed so that the display is divided into cells
called pixels.
ii. There are hundreds of columns and hundreds of rows that intersect in cells
forming a grid superposed on the display.
iii. Each cell or pixel has its own coordinates and its own RGB (red, green and
blue) color components.
iv. Resolution = columns x rows = Number of pixels
v. The higher the resolution the better the quality of the image and the lower
the resolution the lower the quality is.
vi. The resolution doesn’t change with the size of the screen because it is
always a fixed product of the columns and the cells.
vii. Higher resolution requires higher image file volume and faster Internet
access to upload and download it.
6- Spoken words output
a. Computer can also speak words in all languages if we teach it to speak.
b. Spoken words are chosen from a word dictionary and articulated as per a grammar
algorithm.
c. A software help complete this job.
Storage
Computer storage components provide a way for the computer to store and retrieve data and
information needed for its computation operations and allow business people who use the
computer to have needed information available when they need it for their applications.
Storage fall under two categories: Temporary and permanent.
1- Temporary or volatile storage: Needed to store data and application programs during the
processing. It is blank when the power is off. The following components are volatile or
temporary storage components:
a. Registers: Briefly used by the processor to store the numbers to compute and the result
of the computation.
b. RAM (Random Access Memory): It is a memory chip (typically referred to as DRAM,
Dynamic RAM) that can store hundreds of billions of bytes (100 Gigabytes) and more in
most modern computers. It is used as the waiting lobby for all elements used by the
processor to process an application. (Figure 3-3)
c. DRAM solid state storage technology uses semi-conductors; it is a volatile or temporary
memory because its semi-conductors need power to keep the stored items which are
lost when the power is OFF.
d. Because RAM is volatile, files must be saved before you quit the computer or turn it OFF
for any reason and updates should be saved frequently so that they will not be lost
accidently.
e. RAM is divided by the operating system into several compartments each assigned to a
specific type of data or information during the processing, as follow:
i. The operating system compartment
ii. The input compartment
iii. The output compartment
iv. The processing results compartment
v. Interface compartment
vi. This memory allocation should be strictly enforced and no break-in through the
borders must be allowed under any circumstances. Otherwise the system will
break down immediately.
f.
RAM is a must visit temporary stay area for everything that is:
i. Input to the computer
ii. Output from the computer
iii. Input to the processor
iv. Output from the processor
v. Input from all other storage media
vi. Output to all other storage media.
g. Cache: is a solid state volatile fast memory chip. This chip is checked first by the
processor when it looks for instructions or data needed that is why:
i. It is small (kilobytes)
ii. May be dispersed to 2 or 3 levels
iii. Used to store most recently and most frequently used instructions and data to
allow for the fastest possible processor access.
2- Internal permanent storage: When the computer power is off the computer is not dead; it is
sleeping because it will restart when the power is turned ON again! And what about the date
and time that stay running and up when the computer is off?
a. ROM (Read Only Memory): is a permanent solid state storage chip that holds
instructions and data recorded in the factory: (Figure 3-3)
i. Hold the BIOS (Basic Input Output System)
ii. When you turn the power ON the BIOS is activated and takes control of the boot
process by extracting a copy of the operating system kernel from the hard disk
and place it into RAM
iii. When it is fully there the operating system take control and finish the waking-up
process called the booting process.
iv. Mobile computer like the smart phones and PDAs that have no hard
disk (they instead have a flash drive) don’t need any booting. They are
up right when power is ON.
b. CMOS (Complementary Metal-Oxide Semiconductor): Semi-permanent chip
get its power from a tiny rechargeable battery fixed in the mother board. It
holds the following information: (Figure 3-3)
i. Configuration of the computer system to help the BIOS and the operating
system in the booting process.
ii. The date and time always updated shown on the right bottom corner of the
monitor and supplied to all computer components and programs that need
them.
c. Virtual memory (VRAM):
i. Virtual memory is not a chip nor is volatile because it is a part of the HDD
configured as an extension of the actual RAM.
ii. Unlike Cache used to store most recently and frequently accessed items, VRAM
is much bigger storage used to store the least frequently accessed items.
iii. Processor starts looking for needed items as follow: Cache then RAM then
VRAM then other assigned media.
3- Permanent mass storage technology: Includes the primary storage medium, which is
the internal hard disk drive and all other secondary and external storage media where
three different technologies are used:
Figure 3-21 (hard diskmagnetic storage
technology courtesy
Microsoft Gallery)
a. Magnetic technology:
i. This technology represents the most common and strongest removable
mass storage technology
ii. Magnetized surface is populated by magnetic grains (grain size = 10
nanometer = 0.00,000,001 mm).
iii. That surface pass close to read-write magnetic heads that arrange them
into ASCII code in the recording phase and read the arrangement and
convert it into ASCII characters during the reading phase.
iv. The gap between the head and the surface of the medium is
somewhere between 10 and 50 nanometers.
v. A particle of dust or smoke is at least 10 times bigger than the gap that
is why you must:
1. Keep the computer clean and away from dust, smoke and
humidity
2. Never abruptly move the computer or shake it while the hard
disk is spinning.
vi. Examples of magnetic technology are:
1. The hard disk drive (HDD) which was introduced by IBM in 1956
is until today the main mass storage unit of any computer. It is
formed of:
a. Stack of magnetized platters (2.5” diameter in laptop
computers, 3.5” in desktop computers) that spin around
an axis.
b. Beam of read write heads position themselves between
the moving platters.
c. SATA (Serial Advanced Technology Attachment) form
the mass storage interface for data exchange with RAM.
d. Major manufacturers worldwide are: Western digital,
Toshiba and Seagate.
e. HDD estimated worldwide sales may surpass 40 billion
dollars in 2012.
2. Magnetic bands used to store information on the back of most
used cards like:
a. Credit cards
b. Gift cards abundantly used by stores as very popular
gifts that help in the promotion and marketing.
c. Driver licenses and other ID cards.
d. Hotels door opener and similar applications.
3. Magnetic tape: A sequential high endurance mass storage
presently used for backing up extensive mass data because of
their very low cost compared with other media.
b. Optical technology:
Figre3-22: Optical storage
technology courtesy
Microsoft Gallery.
i. This technology uses low-power laser beams to create pits (1-3 microns
long X 0.5 micron wide x 0.1 micron deep) on the mirror like surface of
the disk (12 cm of diameter).
ii. The disk surface comprises a layer of polycarbonate plastic, where the
pits are perforated, covered by a thin aluminum layer that reflects light
where no pits are present and a layer of lacquer that protects the
surface.
iii. In the reading phase the laser beam scans the surface the beam will
have a sharp reflection that represents (1) (no pits = lands) and dim
reflection over the pit (0).
iv. Disk capacity is function of the gap between pits of the medium surface:
1. CDR and CDRW store around .7 megabyte
2. DVDR and DVDRW store 7 gigabytes
3. BDVD stores 25 gigabytes.
v. Optical technology pros:
1. Very high condensation in small area (superior capacity
compared with Magnetic technology).
2. Excellent quality sound and graphics.
3. Inexpensive
4. Recorded data is not affected by power outage and magnetic
field disturbance
5. Disk doesn’t need to be protected into closed boxes and their
scanning devices are durable because they have few moving
parts subject to wear.
vi. Optical technology cons:
1. Very slow compared to other media
2. Cannot be used inside the system unit
3. Rewritable media must be burned and prepared to be able to
erase previous recording before recording again on the same
area.
c. Solid state non-volatile storage technology:
Figure 3-23: USB drive built
with solid state technology
courtesy Microsoft Gallery
i. This technology utilizes non-volatile semiconductors that can be
rewritten electrically and does not require power to retain data.
ii. Two types are available depending on the logic gate used to get the
data: NAND and NOR.
iii. The NAND (Not AND) electronic logic gate technology developed by
Toshiba allows access to a page or bloc of data; it is designed to
ultimately replace the magnetic HDD. It outputs (1) if both inputs are
similar (both ones or both zeroes)
iv. The NOR (Not OR) electronic logic gate technology was developed by
Intel allows access to a single byte in the chip. Produce (1) only if the 2
inputs are zeroes
v. Solid state pros:
1. Used by cache, ROM, Flash memory, Flash drive, smart phones
and so forth to replace HDD.
2. No moving parts
3. Faster and more consistent input/output
4. Requires less power than other storage technologies.
5. Much faster than HDD in supplying needed data to the
processor (much shorter latency)
vi. Solid state cons:
1. Can wear out faster than other media.
2. Read and write operations apply to one complete page.
3. Erase operations apply to a bloc of the page (less operational
flexibility compared to other storage media).
4. Prohibitive cost (2 terabyte of solid state may cost about $
500,000 while a 2 terabytes HDD costs less than $200.
d. Future storage technologies: Holographic data storage system (SSDS)
i. This technology is still under development. Although over half decade of
research and millions of dollars were spent, it was lately introduced in a
LAS VEGAS convention in May 2012 (NAB).
ii. This is a WORM (Write Once Read Many) archival storage technology
that consists of using two laser beams that create 3D holograms to store
pages of data and retrieve them by memorizing the storage angle.
iii. Holograms are stored on top of each other so it can store 1 gigabyte on
2 cubic mm.
iv. Holograms don’t wear fast (life span is over 50 years)
v. Holography disks are well protected from weather, heat, humidity and
handling.
vi. SSDS media are fast and flexible (less than 10 seconds to access any
hologram data.
e. Future storage technology: Molecular storage memory
i. Inspired by DNA principles, scientists aims to develop synthetic strands
in molecules similar to those of the DNA.
ii. The density may be million times higher than other available storage
technology.
iii. This technology is underway and will possibly be the future
breakthrough in the storage industry.
iv. Reading University researchers announced their findings on this subject
in early in 2010 and technology development is underway.