Chapter 3
Hardware
3.01 What are input, output and storage
devices?
3.01 Input, Output and storage Devices
• Input – keyboard, trackerball, microphone, optical mouse,
scanner
• Output– inkjet printer, laser printer, 3D Printer, Speaker,
monitor
• Secondary Devices - hard disks, solid – state drives,
• Main memory - memory chips
• Processor – microprocessor
** touchscreen is both an input and output device
3.01 Input, Output and storage Devices
3.01 Input, Output and storage Devices
• Know how the input and output devices work, check
this CIE online resource:
http://www.cambridgeinternational.org/images/28502
1-topic-1.3.1-input-output-and-storage-devices-9608.pdf
Keyboard
• The most common input device
• it is used for inputting text,
numbers, punctuation marks,
symbols and instructions using a
number of software applications.
• By pressing down a key
completes an electrical circuit.
This circuit then transmits a
binary signal (commonly using
ASCII) to the computer to
represent the key pressed.
Keyboard
• Ergonomic or ergonometric keyboards
are shaped so that the user is less likely
to suffer from RSI (repetitive strain
injury).
• Overlay or concept keyboards consist of
an A4-sized tray that can have an overlay
sheet in it. It is used by people who may
have disabilities as it is easier to press a
large symbol than to press the key on the
keyboard.
Internal Workings of Keyboard
• The keyboard has its own processor and circuitry, a majority of which forms an
important component called key matrix.
• The key matrix is a collection of circuits under the keyboard, which is broken at a
specific point under every key, which results in making the circuit incomplete.
When you press any particular key, it completes this circuit, thus, enabling the
processor to determine the location of the key that was pressed.
• When you type or press any key, a switch is pressed, which completes the circuit
and allows a tiny amount of current to flow. A processor analyzes the position of
the keys pressed and sends this information to the computer, where it is sent to
something called the 'keyboard controller'. This controller processes the
information that is sent by the keyboard's processor, and, in turn, sends it to the
operating system (OS). The OS then checks this data to analyze if there are
system commands otherwise it forwards the information into the current
application.
Tracker ball mouse
• A tracker ball is an upside down mouse-like
device.
• It has been designed for users who have limited
ability regarding movement of their fingers or
hands. The user moves the ball using palm or
finger to control the pointer on the screen.
• There are usually three buttons, two same as left
and right click buttons on a mouse while third
button is usually used instead of double click. It is
useful where the user has limited motor skills or
where there is a lack of space.
How does a trackerball work?
• Trackballs work by using optical sensors to read the movements of dots on the
surface of the ball. By tracking the direction in which the dots move, the optics
translate the movement of the ball into moving the cursor.
• Older trackball units use rollers or wheels to record the movement of the ball
within an enclosed housing. Friction of the ball against these surfaces turns small
drive wheels, which the device records as movement on an X and Y axis. The
wheels have small wire contact discs on them that would pulse an on and off
signal as the wheel rotated and created a circuit. Computers then translated the
amount of pulses in the signal to cursor movements.
• Later variations replaced the contacting disks with a similarly shaped wheel
marked with holes. LED light is then displayed through the holes, and read by an
optical sensor. As light passes through the holes to the sensor or is interrupted by
the spinning wheel, it creates a pulse similar to earlier models.
Optical mouse
• An optical computer mouse uses a light source, typically a lightemitting diode, and a light detector, such as an array of
photodiodes or an image sensor, to detect movement relative to a
surface.
• It is an alternative to the mechanical mouse, which uses moving
parts to perform the same function.
• When a mouse is connected with the computer, a red LED starts
glowing. This light is focused on the surface beneath the mouse by
a special type of lens (HDNS-2100). The reflected light falls back to
the camera integrated in Optical Mouse Sensor.
• The camera takes images of the surface with a frequency in the
range of 1500 to 6000 images per second to calculate the position
of mouse. These images are processed by Digital Signal Processor
(DSP) and resultant co-ordinates are sent to the PC. The driver of
the mouse installed in the computer receives the co-ordinates and
makes the cursor move on the screen accordingly.
Microphone
• Microphones are a type of transducer - a device which
converts energy from one form to another.
Microphones convert acoustical energy (sound waves)
into electrical energy (the audio signal).
• Different types of microphone have different ways of
converting energy but they all share one thing in
common: The diaphragm. This is a thin piece of
material (such as paper, plastic or aluminium) which
vibrates when it is struck by sound waves. In a typical
hand-held mic like the one below, the diaphragm is
located in the head of the microphone.
• When the diaphragm vibrates, it causes other
components in the microphone to vibrate. These
vibrations are converted into an electrical current which
becomes the audio signal.
• Note: At the other end of the audio chain, the
loudspeaker is also a transducer - it converts the
electrical energy back into acoustical energy.
Touchscreens
• Both an input and output device
• Can be resistive or capacitive touchscreen
Resistive touchscreen
• The resistive touch technology is the most
widely used touch technology today. A
resistive touchscreen consists of two thin
flexible metallic layers with a gap in between.
These two layers have an electric current
running through them. When touched the top
flexible layer touches the bottom one,
interrupting the electrical current. The device
notices this and detects the point of contact by
the change in electrical flow. Of course this all
happens at warp speed.
• Applications: ATM, POS terminals
Resistive touchscreen
• Resistive touch is one of the cheapest
touch technologies out there. A resistive
touchscreen responds to pressure and
doesn't care what object applies the
pressure. A finger, glove or stylus will all
work. Swiping and multi touch do not
work, because this technology only
registers one touch point. That is why a
resistive touchscreen doesn't work on
smartphones or tablets
Capacitive touchscreen
• A capacitive touchscreen uses a transparent electrode layer. This
layer is placed on top of a glass panel and covered by a protective
layer. When a finger touches the touchscreen, some of the electrical
charge transfers from the screen to the user. Sensors in all four
corners of the screen detect the decrease of electric current. The
controller than determines the touch point.
• Capacitive touchscreens can only be activated when touched by
human skin or a stylus holding an electrical charge. Despite its long
term popularity, capacitive touch now gets replaced by projected
capacitive touchscreens.
Capacitive touchscreen
Scanner
• Scanners are used to enter hardcopy images into
a computer. The most common type is the
flatbed scanner where the user places the
document flat on a glass panel and closes the lid.
• An array of light sensors and a light source move
underneath the document.
• The sensor ‘reads’ the light reflected from the
document or image. Most scanners use chargedcoupled device (CCD) array. Regardless of the
technology used, a sensor array contains lightsensitive diodes that convert analog light waves
into a digital signal. Some scanner arrays contain
three rows of sensors. Each row is calibrated to
measure red, blue or green light
How does a scanner work?
• Once the document is in place and the lid is closed, a moving belt slides a
light source across the entire surface of the document. The motor in a
scanner is finely tuned to make sure this light source travels at the same
speed and creates the same amount of light across the whole document,
ensuring a uniform exposure. The light shined on the document then
reflects back into the machine and is reflected onto the lens by a series of
mirrors.
• The optic information from a scanner sensor is turned into digital pixel
information in order to be saved as a digital file, such as a JPG, PNG or TIFF.
A scanner relays this information to a computer through a wireless or
connecting cable connection to save the digital file. After the transfer, the
image file of the document is accessible on the computer and can be
opened, saved, edited or deleted just like any other digital picture file.
Output Devices
• A printer is a peripheral which makes a persistent human-readable
representation of graphics or text on paper or similar physical media.
• Impact printers rely on a forcible impact to transfer ink to the media.
The impact printer uses a print head that either hits the surface of the
ink ribbon, pressing the ink ribbon against the paper (similar to the
action of a typewriter), or hits the back of the paper, pressing the
paper against the ink ribbon (the IBM 1403, or dot matrix printer for
example)
• Non-impact is a type of printer that does not operate by striking a
head against a ribbon. Examples of nonimpact printers include laser
and ink-jet printers.
Inkjet Printer
• Inkjet printing is a type of computer
printing that recreates a digital
image by propelling droplets of ink
onto paper, plastic, or other
substrates. It works by spraying
ionized ink at a sheet of paper.
Magnetized plates in the ink's path
direct the ink onto the paper in the
desired shapes. Ink-jet printers are
capable of producing high quality
print
Types of Inkjet Printers
• Different types of inkjet printer fire the ink in various ways. In Canon
printers, the ink is fired by heating it so it explodes toward the paper
in bubbles. This is why Canon sells its printers under the brand name
"Bubble Jet." Epson printers work a slightly different way. They use an
effect called piezoelectricity. Tiny electric currents controlled
by electronic circuits inside the printer make miniature crystals jiggle
back and forth, firing ink in jets as they do so. You can think of inkjet
printers very simply as a firing squad of nozzles rattling off millions of
dots of ink at the paper every single second!
• Video of inkjet printhead
How does Inkjet Printer work?
How does Inkjet Printer work?
Laser Printer
• This type of printer produces very high
quality hard copy. It consists of drum
that is electrically charged. A laser is
used to change the charge on the
drum for each dot of the output to be
produced. Electrically charged toner is
then attracted to the oppositely
charged dots.
• The paper presses against the
toner coated drum and is output with
the pattern of dots required which is
then heated in order to permanently
fuse the text/imagery. The page
cannot be printed until the whole
document has been stored in a large
buffer
• Video of Laser Printing process
How does a laser printer work?
• Millions of bytes or characters of data move from the computer to the printer. Then
the electronic circuit present in the printer must figure out how to print the data that
it has received. This is where the printer determines how to print the data so that it
looks correct on the page. This is also when the electronic circuit activates the
corona wire, which is a high-voltage wire. The corona wire gives off a static electric
charge and effectively charges the photoreceptor drum.
• Once the photoreceptor drum is charged up, it will gain a positive charge across its
surface. While this is happening, the circuit will bring the laser to life. It will ask the
laser to draw the image of the page on the drum. The laser does not have to move as
it will bounce its laser beam off of a moving mirror, which is then run over the drum.
Soon the whole image will appear on the drum and then the ink roller will touch the
drum. Now the toner has a positive electrical charge so it can stick to the negative
electrical charge parts on the photoreceptor drum. A sheet of paper is fed through
the printer and the piece is printed.
Speaker
• It is a device which produces sound as output. The
digital data from the computer is converted into
analogue signals by a digital to analogue converter
and are then amplified and output using the
speakers. At the front of a loudspeaker, there is a
fabric, plastic, paper, or lightweight metal cone. The
inner part is fixed to an iron coil (sometimes called
the voice coil) that sits just in front of a permanent
magnet (sometimes called the field magnet).
• when electric current is passed through coil; It
becomes a temporary magnet (electromagnet). As
the electricity flows back and forth in the cables, the
electromagnet either attracts or repels the
permanent magnet. This moves the coil back and
forward, pulling and pushing the loudspeaker cone
which produces sound.
3D Printer
• 3D printers are a new generation of machines that can make everyday
things. They’re remarkable because they can produce different kinds of
objects, in different materials, all from the same machine.
• A 3D printer can make pretty much anything from ceramic cups to plastic
toys, metal machine parts, stoneware vases, fancy chocolate cakes or even
(one day soon) human body parts.
• The 3D printing process turns a whole object into thousands of tiny little
slices, then makes it from the bottom-up, slice by slice. Those tiny layers
stick together to form a solid object. Each layer can be very complex,
meaning 3D printers can create moving parts like hinges and wheels as part
of the same object.
How does a 3D Printer work?
• 3D printers create solid objects from various materials. A blueprint for the
object is created with CAD or modeling software and sent to the printer via
a connected computer. Either the modeling software or a separate piece of
software called a "slicer" divides the blueprint into thin layers, and the
printer prints these layers one at a time.
• The 3D printer usually sprays or squeezes the material onto a platform
layer by layer in passes that are similar to the mechanics of an inkjet
printer. Layers are usually about 1/10 millimeter in size, but printers exist
that are capable of printing even thinner layers. The printer also fuses the
new layer with the previous layers as it makes its passes.
• The actual printing of an object can take anywhere from a few hours to a
few days, depending on a number of factors, such as the type of printer
and the object's size.
Secondary Storage Devices
• Backing storage (also called auxiliary storage) stores programs and
data for future use. In order to store data while the electricity is
switched off or unavailable storage must be non- volatile.
• Access to backing storage is slower than internal memory. Operating
systems and program files are loaded into RAM from backing storage
when required for execution. There are three different types of
backing storage device:
• Magnetic storage device
• Optical storage device
• Solid state storage device.
Hard Disk
• Hard disk is a type of magnetic storage.
It consists of one or more disks
(depending upon the capacity of hard
disk).They are mounted on a spindle
which is operated by a motor to spin
the disk very quickly.
• There is usually one read/write head
for each disk surface being used.
• The disks are used to store operating
system as well as software programs
and data files. It provides very fast
access to data for both reading from
and writing to the to the disks.
Hard Disk Components
Platter - Metallic disks where One or both sides of the platter are magnetized, allowing
data to be stored. The platter spins thousands of times a second around the spindle. There
may be several platters, with data stored across them
Head - The head reads magnetic data from the platter. For a drive with several platters,
there may two heads per platter allowing data to be read from top and bottom of each
Actuator Arm - used to move the read heads in and out of the disk, so that data can be
read and written to particular locations and you can access data in a Random fashion, you
don't need to read your way through the entire disk to fetch a particular bit of
information, you can jump right there. Seek time is very low.
Power connector - provides electricity to spin the platters, move the read head and run
the electronics
IDE connector - allows for data transfer from and to the platters
Jumper block - used to get the disk working in specific ways such as RAID
How Hard Disk Reads Data
The text below explains how a hard disk works:
1. The platters spin around the spindle
2. data is requested to be read from a particular area of a platter
3. the actuator arm moves the read head to that track
4. Once the data sector that is required has spun around and under
the read head, data is read
5. Read data is sent from the IDE connector to main memory
How Hard Disk Writes Data
1. The platters spin around the spindle
2. data is sent to the hard disk using the IDE connector
3. the actuator arm moves the write head to the track that will be
written to
4. Once the data sector that is required has spun around and under
the write-head, data is written to the platter
Optical Disc
• optical
disc recording technologies, an
optical disc (OD) is a flat, usually circular disc
which encodes binary data (bits) in the form
of pits (binary value of 0 or off, due to lack of
reflection when read) and lands (binary value
of 1 or on, due to a reflection when
read) on a special material (often
aluminum) on one of its flat surfaces
• These pits and lands do not represent the 1s
and 0s, rather each change from pit to land or
land to pit is interpreted as 0 while no change
is read as 1.
Optical Disc
How Data are Written into and Read from CD
• The burning (writing) process of a CD is nothing but creating a pattern of pits and
lands over the polycarbonate layer. But since the data must be accurately
encoded on such a small scale, the burning process must be extremely précised.
A CD burner is used to write (burn) the data on a CD. It incorporates a moving
laser quite similar to a CD player which is known as ‘Write Laser’. The Write Laser
which is more powerful than the ‘Read Laser’, has the capability to alter the
surface of CD instead of just bouncing the laser light off. During burning process,
as per the data (binary values) the Write Laser bounces the light beam over the
CD surface and creates a series of pits on it.
• When you play (read) the CD, the Read Laser bounces the light beams (not
capable to modify the surface of CD) on the surface and detects the pits and
lands. Each change between pit to land or vice versa is translated as zero and no
change (pit to pit or land to land) is translated as one. These binary values form
the actual data.
Solid state memory
• Solid state storage is a type of computer
storage media that is made from silicon
microchips. it stores data electronically instead of
magnetically, as spinning hard disk drives or magnetic
tape do.
• An important advantage of solid-state storage is the fact
that it contains no mechanical parts, allowing data
transfer to and from storage media to take place at a
much higher speed and providing a more predictable
lifespan for the storage media.
• In addition to providing faster and more consistent
input/output (I/O) times, solid-state storage media offers
the same levels of data integrity and endurance as other
electronic devices and requires less power and cooling
than its electromechanical equivalents. It also generally
weighs less.
How does a Solid State Drive work?
• SSDs serve the same purpose as HDDs: they store data and files for longterm use. The difference is that SSDs use a type of memory called “flash
memory,” which is similar to RAM—but unlike RAM, which clears its data
whenever the computer powers down, the data on an SSD persists even
when it loses power.
• If you took apart a typical HDD, you’d see a stack of magnetic plates with a
reading needle—kind of like a vinyl record player. Before the needle can
read or write data, the plates have to spin around to the right location.
• On the other hand, SSDs use a grid of electrical cells to quickly send and
receive data. These grids are separated into sections called “pages,” and
these pages are where data is stored. Pages are clumped together to form
“blocks.”
• SSDs are called “solid-state” because they have no moving parts.
Flash Memory
• a type of electronically erasable programmable read-only memory
(EEPROM)
• is a solid-state chip that maintains stored data without any external
power source. It is commonly used in portable electronics and
removable storage devices, and to replace computer hard drives.
• Present in smartphones, GPS, MP3, PC, USB, digital camera
• Solid-state drives (SSD) using flash memory are replacing hard drives
in netbooks and PCs and even some server installations. Needing no
batteries or other power to retain data, flash is convenient and
relatively foolproof.
How Flash Memory Stores Data?
• The transistors in flash have two gates
on top, one called a control gate and
one called a floating gate.
• The two gates are separated by oxide
layers through which current cannot
normally pass. In this state, the
transistor is switched off—and
effectively storing a zero.
How Flash Memory Store Data?
• How to turn on the transistors?
• Both the source and the drain regions are
rich in electrons (because they're made of ntype silicon), but electrons cannot flow from
source to drain because of the electron
deficient, p-type material between them.
• But if we apply a positive voltage to the
transistor's two contacts, called
the bitline and the wordline, electrons get
pulled in a rush from source to drain.
• A few electrons also manage to wriggle
through the oxide layer by a process called
tunneling and get stuck on the floating gate:
The presence of electrons on the floating
gate is how a flash transistor stores a one.
Primary Memory
Main Memory
• Random Access Memory (RAM)
• Dynamic RAM (DRAM) example: predominant form of main memory in
modern computers.
• Static RAM (SRAM) example: cache memory
• Read – Only Memory (ROM)
• Used typically in a PC for boot program code
• Devices such as washing machine for storage of program code
Primary / Main Memory
• Main store (or computer memory) is divided into Read Only Memory
(ROM) and Random Access Memory (RAM).
• CACHE MEMORY – A Type primary storage where the computer can
temporarily store blocks of data used more often.
• REGISTER – these are parts of the CPU with the least capacity, storing
extremely limited amounts of instructions and data only immediately
before and after processing
Read Only Memory (ROM)
• ROM is memory that cannot be changed by a program or user. ROM
retains its memory even after the computer is turned off. For
example, ROM stores the instructions for the computer to start up
when it is turned on again
• Common Data found in ROM:
•
•
•
•
•
Boot program (or known as the BIOS) to start the computer
Fonts used in laser printer
Character pattern memory
Firmware updates for hardware ex. Cartridges used in video game consoles
Embedded system (software) used in cooking / washing timings
Programmable read only memory (PROM)
• A PROM is a memory chip on which data can be written only once.
Once a program has been written onto a PROM, it is permanent.
Unlike RAM, PROM's retain their contents when the computer is
turned off. The difference between a PROM and a ROM (read only
memory) is that a PROM is manufactured as a blank memory,
whereas a ROM is programmed during the manufacturing process. To
write data onto a PROM chip, a special device called a PROM
programmer or PROM burner is required.
Erasable programmable read only memory
(EPROM) and EEPROM
• EPROM is a special type of PROM that can be erased by exposing it to
ultraviolet (UV) light. Once it has been erased, it can be reprogrammed using an EPROM burner.
• An EEPROM is a special type of PROM that can be erased by exposing
it to an electrical charge. Like other types of PROM, EEPROM retains
its contents even when the power is turned off
RAM
• RAM is a fast temporary type of memory in which programs,
applications and data are stored. Here are some examples of what's
stored in RAM:
• the operating system
• Applications
• the graphical user interface (GUI) If a computer loses power, all data
stored in its RAM is lost
• Has 2 types: SRAM and DRAM
DRAM
• DRAM stores data by “writing a charge to the capacitor by way of an access
transistor” and was invented in 1966 by Robert Dennard at IBM and was patented
in 1967.
• SRAM makes use of latches in order to store data (transistor circuit), whereas
DRAM uses capacitors for storing bits in the form of charge.
• DRAM takes 1 transistor and 1 capacitor to store 1 bit. Means Each memory cell
in a DRAM chip holds one bit of data and is composed of a transistor (acting as
switch to read the capacitor) and a capacitor(responsible for holding the data of 1
or 0). But, capacitor leaks, so, they have to be recharged periodically making the
DRAM slower than SRAM
• Slower because access time for DRAM is about 60 nanoseconds than SRAM with
10 nanoseconds only
• Common application: DDR3 in computers
SRAM
• SRAM (static RAM) is random access memory (RAM) that retains data bits
in its memory as long as power is being supplied.
• Unlike dynamic RAM (DRAM), which stores bits in cells consisting of a
capacitor and a transistor, SRAM does not have to be periodically
refreshed.
• SRAM takes 6 transistors to store 1 bit while DRAM uses 1 capacitor and 1
transistor only, making SRAM more complex in structure
• Static RAM provides faster access to data and is more expensive than
DRAM.
• SRAM is used for a computer's cache memory and as part of the random
access memory digital-to-analog converter on a video card.
3.02 Main Memory
Oct/Nov 2016 Paper 11#4
#4 Describe the basic internal operation of :
a. Keyboard
b. Optical disc
c. Optical mouse
d. Scanner
Oct/Nov 2016 Paper 11#4
Oct/Nov 2016 Paper 11#4
May/June 2017 Paper 12#2
May/June 2017 Paper 12#2
Worksheet
3.03 Logic Gates and Logic Circuits
Logic Gates
• Draw a logic circuit
from the following
logic expression
May/June 2015 Paper 11#7
Solution
Alternatives
Worksheet