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Chapter 10 : Computer Peripherals

_________ are devices that are external to the main processing function of the computer itself. They are external to the CPU. They do not include the CPU, memory and power supply.
The peripherals in a mainframe computer are similar, except larger, with more capacity. They may be 100 keyboards and terminals and a hard drive array.
Peripheral devices are classified as input devices, output devices and storage devices.
Each peripheral is connected to the computer by one of two methods. State them.
1) Ports
parallel, serial, USB or FireWire
2) Or an interface to the system bus
Computer storage is often conceptualized hierarchically, based upon the speed with which data can be accessed.
In the hierarchy of storage, access to CPU __________ is essentially instantaneous, since they are actually a part of the CPU.
In the hierarchy of storage, _____________ is the fastest memory outside the CPU.
Cache memory
______________ is a small amount of fast memory that is used to hold current data and instructions.
Cache Memory
_________ storage refers to both types of RAM, DRAM and SRAM.
Both DRAM and SRAM provide immediate access to program instructions and data by the CPU and can be used for the execution of instructions.
True (Test Question)
______ storage refers to hard drives, thumb drives, CD-ROMs/DVDs, floppy drives and magnetic tape.
Data and programs in secondary storage must be copied to primary storage (memory) for CPU access.
True (Test Question)
Most secondary devices are mechanical in nature and are therefore slower than primary memory. The only exception is flash memory.
The location of the desired data is usually not immediately accessible, and the medium must be physically moved to provide access to the current location. The _________ is the time needed to find the desired location.
seek time
Most of the access time specified for secondary storage devices consist of seek time.
State the two advantages of secondary storage.
1) its permanence, or lack of volatility and
2) it may be used to store massive amounts of data
Magnetic tape, most flash memory devices, optical disks and some magnetic disks are designed for easy removal from the computer system, which makes them well suited for backup and off-line storage of data that can be loaded when the data is needed.
Data and programs may be stored on a secondary storage device connected to a different computer and accessed through a network connection between the computers. In this context, the computer with secondary storage is known as a server or file server. The primary purpose of the file server may be to act as a storage provider for all of the computers on the network.
Flash memory is nonvolatile electronic integrated circuit memory. Although read accesses and certain simple overwrite accesses are relatively fast, flash memory must be erased in blocks. The erase-and-rewrite operation is very slow compared to the read access.
Thumb drives are useful for moving files and data from one machine to another and also serve as an inexpensive and convenient backup medium.
Large capacity flash memory units called "_________" have appeared on the market and are starting to supplant disk drives as the long-term storage device of choice in computers where less weight, low power consumption and small size are important. They have the additional advantage of being relatively immune to failure due to physical shock and vibration, and generate less heat and no noise.
Solid State Drives
A __________ consists of one or more flat, circular platters made of glass, metal, or plastic, and coated with a magnetic substance.
Particles within a small area of the magnetic substance can be polarized magnetically in one of two directions with an electromagnet. An electromagnet can also detect the direction of polarization previously recorded. Magnetic polarization can be used to distinguish 1's and 0's.
Electromagnetic read/write heads are used for this purpose.
A drive motor rotates the disk platter(s) about its central axis. On most drives, the motor rotates at a fixed speed.
An ______ resembling that of a phonograph record player has the read/write head mounted at the end. It makes it possible for the read/write head to move radially in and out across the surface of the disk. The read/write head motor controls precisely the position of the arm on the disk.
actuator arm
State the two major types of magnetic disks.
1) Floppy disks or diskettes
2) Hard disks
The floppy disk has ___________ surfaces on the disk platter within the diskette case.
Most hard disk drives contain several platters, all mounted on the same axis, with read/write heads on each surface of each platter. The actuator arm heads move in tandem, so they are positioned over the same point on the surface. Each side of the platter has an actuator arm that can read and write data for that side of the platter.
With the actuator arm head in a particular position, it traces out a circle on the disk surface as the disk rotates. This circle is known as a ______. Each one contains one or more blocks of data.
Since each of the tracks on each surface of the platters all line up, the set of tracks for all of these surfaces form a _____________.
On most disks, the surface of the disk platter is divided into equally sized pie shaped segments, known as __________. Each one contains one block of data, typically 512 bytes, which represents the smallest unit that can be independently read or written.
On a floppy disk, if you assume that the number of bytes in a sector is the same anywhere on a disk, the bits on the disk are more closely packed on the inner tracks than they are on the outer tracks.
In _______, the tracks near the center have the smallest number of sectors per track and the number of sectors increases as the tracks get larger. Each track on an IDE drive is designed to have the optimum number of sectors appropriate to the size of the track. There are still 512 bytes per sector for every sector on the drive.
multiple zone recording
Each platter on the hard drive is made of rigid material and is precisely mounted
The actuator arm heads do not actually touch their side of the platter
A _____ occurs when the actuator arm comes in contact with a platter.
head crash
The hard disks are sealed to prevent dust particles from getting between each side of the platter and the actuator arm head
When the disk is stationary, the actuator arm head rests in a parked position on the edge of the drive. The head has an aerodynamic design, which causes it to rise on a cushion of air when the disk platter spins.
The speed of a hard disk is measured by the sum of its average seek time, latency and sustained transfer rate.
True (true)
__________ is the time required to move from one track to another.
Average Seek Time
_________________ is the time required for disk to rotate to beginning of correct sector.
__________ is the time required to transfer a block of data to the disk controller buffer.
Transfer Time
A single data block consists of a header, 512 bytes of data and a footer.
A(n) ________separates the block from neighboring blocks.
Inter-block Gap
The track positions, blocks, and headers must be established before the disk may be used. The process of doing this is called _______________ the disk.
The entire track is laid down as a serial stream of bits.
Many current hard drives include a large buffer memory that can hold several blocks of data.
true (test question)
A _____________ is a hard drive that is housed in a cartridge that can be removed from the computer.
Removable hard Drive
In a ___________ drive, a cushion of air keeps the head from touching the surface. Thus, the cartridge has the advantage of a hard disk drive, but with the flexibility of an inexpensive, removable cartridge. Zip drives are an example of this technology.
A ____________ is a grouping of two or more disk drives. It can be used to reduce overall data access time by sharing the data among multiple disks and also to increase system reliability by providing storage redundancy.
Disc Array
____________ is a very useful disk array and can be implemented in two ways. These two ways are a mirrored array and a striped array with parity.
A __________, in a RAID configuration, consists of two or more disk drives where each disk drive is identical. The disks each contain exactly the same data. Reads are faster since some of the data can be obtained from each of the hard drives. All data must be written to each of the hard drives.
Mirrored array
A ________, in a RAID configuration, requires a minimum of three disk drives. Some of the data is stored on each of the drives along with parity information (error checking information). If one of the drives goes bad, a new drive can be obtained and the data can be reconstructed with the help of the parity information.
Striped array with parity
A mirror array (RAID 1) and a striped array with parity (RAID 5) are examples of a fault-tolerant system.
Optical storage technologies are portable and are capable of packing a relatively large amount of data into a convenient package. It is intended more for offsite archiving, as well as program and file distribution
A ______________ is a read-only, removable medium with data storage capacity of about 700 MB. Data are stored in blocks on the disk. The blocks can be arranged in files, with a directory structure similar to that of magnetic disks.
A mirrored array (RAID 1) and a striped array with parity (RAID 5) are examples__________.
of a fault-tolerant system
Rather than concentric tracks, data on a CD-ROM is stored on a single track, approximately three miles long, which spirals from the inside of the disk to the outside. Instead of sectors, the data is stored in linear blocks along the track. Each block is the same length.
Data is stored on the disk in the forms of pits and lands. They are burned into the surface of the disk with a high-powered laser. The disks are reproduced mechanically using a stamping process. The disk is protected by a clear coating.
A laser beam is reflected off the pitted surface of the CD-ROM as the motor rotates the disk. The reflection is used to distinguish between the pits and lands, and these are translated into bits.
On a CD-ROM, a "0" bit is represented as a _________.
On a CD-ROM, a "1" bit is represented as a _____________.
When the laser strikes land, light reflected into the light detector.
When the laser strikes a pit, light is scattered.
___________ is essentially similar to CD-ROM technology. The disks are the same size and formatted similarly. However, the use of a laser with a shorter light wavelength (visible red, instead of infrared), allows tighter packing of the disk. Each layer can hold approximately 4.7 GB.
DVD technology
Two layers of data can be placed on the same side of the DVD disk, one underneath the other. In addition, both sides of a DVD-ROM can be used. If both layers on both sides are used, the DVD-ROM capacity is approximately 17 GB. The use of a blue laser extends this capacity to approximately 50 GB.
________ disks were originally designed to provide an inexpensive way for archiving data. WORM disks can be written, however once written, a data block cannot be rewritten. When a file is updated, it is simply written again to a new block and a new directory entry is provided.
Write once, read many times.
WORM disks work similarly to a CD or a DVD. The main difference is that the disk is made is made up of material that can be blistered by a medium-powered laser. Initially, the entire disk is smooth. When data is to be written, the medium-power laser creates tiny blisters in the appropriate locations. These correspond to the pits in a normal CD-ROM.
State the other types of optical storage technologies that medium-powered laser blister technology is also used.
_____________ is a sequential medium, which makes it impractical for random access tasks. Generally, full system backups are made to it and moved to offsite locations for long term storage. It can be used for archival purposes and for disaster recovery. It can be stored indefinitely.
Magnetic Tape
Tape cartridges are read serially and are used for data backup.
True (Test Question)
When the tape is in the tape drive, ready for operation, it is said to be mounted.
State the three types of magnetic tape and briefly describe each one.
The reel-to reel tape drives are used in older mainframe computers to preserve the long-term legacy data.
Linear recording cartridge
This technique used for storage and retrieval is called data streaming.
Helical scan cartridge
The data on helical scan cartridges is very tightly packed, using a read/write head that rotates at a high speed to pack the tape more tightly with data.
The LTO (linear tape open) formats are representative of linear recoding cartridges.
State two different helical scan cartridges in common use.
The smaller AIT (advanced intelligent format) uses 8-mm wide tape in tape lengths of up to 246 meters, with a current maximum uncompressed capacity of 400 GB in a cartridge.
The larger SAIT (super-AIT) cartridge contains up to 640 meters of one-half inch wide tape, with a current maximum uncompressed capacity of 800 GB.
A _________ is an image made up of thousands of individual pixels (picture elements) arranged to make a large rectangular screen. Each pixel is a tiny square on it.
The size of the display is the diagonal length of the screen.
A _____________ pixel is actually made up of a mixture of different intensities of red, green and blue (RGB). It takes one byte per pixel to represent a 256-color image. 24 bit color would use 8 bits per color and result in more than 16 million colors on the screen and is sometimes described as True Color.
A _______________ scale with no shading would require only one 1 bit per pixel (on for white, off for black).
The actual display is produced by scanning and displaying each pixel, one row at a time, from left to right, top to bottom. This method of displaying all the pixels is known as a ___________. It is essentially identical to the way that television pictures are generated.
Raster scan
Some monitors __________ the display, by displaying the odd rows first and coming back and displaying the even rows.
Interlaced monitors tend to flicker more than noninterlaced ones.
True (Test Question)
Noninterlaced displays are also sometimes called ______________.
An alternative to raster scan is _____________, in which pixels are displayed in whatever order is necessary to trace out a particular image. It could trace a character by following the outline of the character. It is used for object images in CAD/CAM applications. They are sometimes used when printing object graphics-based drawings to a plotter.
vector scan
The popularity of what-you-see-is-what-you-get (WYSIWYG) output requires the ready availability of different fonts and flexibility in layout on the screen.
___________ are described by an object-based description language such as PostScript. These fonts can be scaled easily to different sizes and rotated to different angles. The graphic image is then reconstructed at the terminal by translation software that is built into the display controller. This method is particularly amenable to printers and to PostScript displays used for precision graphical and layout work.
Outline fonts
____________ are described by laying out the detailed pixel diagram for the characters.
Bitmapped fonts
____________ technology has become the prevalent means of displaying images.
Liquid Crystal display (LCD)
In a LCD, a florescent light panel, located behind the display, produces white light.
Explain the operation of a LCD Display.
Polarizing filter: light so that most of it in one direction.
The polarized light passes through a matrix of liquid crystal cells. In a color display, there are 3 cells positioned properly for each pixel.
When an electrical current is applied to one of these cells, the molecules in the cell spiral.
The light coming out of the crystal is now polarized in different directions, depending on the strength of the current that was applied to the crystal.
The light is now passed through a red, blue or green color filter.
The final polarizing filter blocks all light that is polarized perpendicular to its preferred direction, the second filter will only pass through the light that is polarized in the correct direction.
Therefore, the brightness of the light is proportional to the amount of polarization twist that was applied by the liquid crystal's spiral.
For a(n) ___________ monitor, there is one transistor per cell in the matrix. It guarantees that each cell will receive a strong charge. It is more expensive and difficult to manufacture. It has a brighter picture.
active matrix
For a(n) _____________ monitor, there is one transistor per row and column in the matrix. Each cell is lit in succession. The display is dimmer since pixels are lit less frequently.
passive matrix
CRT (Cathode Ray Tube) was the most common display technology. It is similar to TVs. CRTs have been replaced by LCDs.
Describe how a CRT works.
Three electron guns within the tube shoot beams of electrons from the back of the tube. There is a gun for each of the primary colors; red, green and blue.
A high voltage applied to the inside of the face of the tube attracts the beams to the face. The face of the tube is painted with tiny dots or stripes of phosphors, which glow when struck by electrons. There are phosphors that glow red, blue and green.
A shadow mask in the tube is designed such that the electrons from each gun can strike only phosphors of the matching color.
The strength of the beams varies depending on the color and brightness of the point being displayed.
The stronger the beam for a particular color, the brighter that color appears on the screen.
The three beams of electrons are deflected both horizontally and vertically by a pair of electromagnetic coils to form a raster scan.
(linear tape open) formats are representative of linear recoding cartridges.
A __________________________ works identically to a CRT except there is only one electron gun, the phosphor is white, yellow or green, and no shadow mask is required.
text monitor (monochrome video monitor)
Text monitors are usually 24 lines x 80 characters. A character is the smallest unit on a screen. Very little memory is required for text monitors and remote transmissions are fast.
OLED (Organic Light-Emitting Diode) technology is a new screen technology that is poised to supplement or replace LCD technology in display monitors.
___________ technology offers an image that is brighter, with colors that are more vivid and with vastly improved contrast. Despite the improved image, the OLED panel consumes less power, with a package that is even thinner than current flat screen monitors.
OLED (Organic Light Emitting Diode)
LCD technology is _______ in the sense that light is generated by a backlight; the light is selectively blocked by the LCD cells in the panel. Leakage in the cells limits the level of darkness that can be achieved and the maximum brightness is limited by the brightness of the backlight.
In contrast, OLED technology is ____________. OLED technology consists of a thin display panel that contains red, green, and blue LEDs for each pixel with transistors for each LED that generate electrical current to light the LED. The light output is produced directly by these LEDs. The brightness of a pixel is determined by the amount of current supplied by the transistor, which in turn is determined by an input signal indicating the desired level of brightness. The simplicity of the panel, combined with the lack of need of a backlight, result in the thinness of the panel.
Early printers were derived from typewriters. Printing resulted from the hammer-like physical impact of the character through inked ribbon onto paper.
Later impact printing used pins that were selectively employed to generate dot matrix representations of the characters on the page. These printers were known as dot matrix printers.
All modern printing is done using nonimpact printing.
Like displays, printer output can be character based or graphics based.
Nearly all modern computer printers produce their output as a combination of dots, similar in style to the pixels used in display.
Explain the two major differences between dots and pixels.
1) The number of dots per inch printed is generally much higher than the number of pixels per inch displayed. There are 70 to 150 pixels per inch on the monitor and 600 to 2400 dots per inch on the paper.
2) The dots produced by most printers are either on or off and pixels have an infinite range of intensity or brightness.
The output to many printers takes the form of graphical bitmaps that represent the required pixels directly.
Some printers have built-in computing capability and can accept data in the form of a page description language, predominately Adobe PostScript or PCL. The controller in the printer can then convert from the page description language to the bitmap within the printer itself. Memory is provided within the printer to hold the bit-mapped image while it is being printed.
State the various types of printers.
Typewriter / Daisy wheels (obsolete)
Dot matrix
Thermal wax transfer
Dye Sublimation
Laser Printer
_____________ use impact printing, because printing results from the physical impact of a print head on the paper.
___________squirt boiled droplets of ink as the print cartridge moves across the page to print a row and mechanical rollers move the page downward to print successive rows.
Inkjet Printers
The heat, from the print heads of a ___________ printer, melts the wax onto ordinary paper.
Thermal Wax Transfer
The heat, from the print heads of a ________ printer, melts the dye onto special paper. The dye diffuses in this paper so that the color of dots actually blends together. It can print continuous color tones.
Dye Sublimation
___________ printing is derived from xerography. The major difference is that the image is produced electronically from the computer using a laser or light-emitting diode, rather than scanning a real image with a bright light, as in a copy machine. Laser printing requires the interaction of mechanical, electrical and optical technologies. The toner is placed on a negatively charged rotating drum. The drum deposits the toner on positively charged paper as the paper moves through the system.
Color images are produced by printing the sheet four times with different colored toners.
List the six steps in the operation of a laser printer.
In the ____________ step of a laser printer printing a page, the drum is cleaned of any residual toner with a rubber blade and a fluorescent lamp removes any electrical charge remaining on the drum.
In the __________ step of a laser printer printing a page, the entire drum is uniformly charged to -600V by the primary (or main) corona wire located inside the toner cartridge.
In the _____________ step of a laser printer printing a page, the laser printer controller uses a laser beam and a series of mirrors to create the image of the page on the drum.
In the ________ step of a laser printer printing a page, the developing roller, located inside the toner cartridge, has a magnet inside of it that attracts the iron particles in the toner. As the developing roller rotates by the drum, the toner is attracted to the areas of the drum that have been exposed by the laser, creating the print image on the drum.
In the _____________ step of a laser printer printing a page, a strong positive charge is placed on the paper patiently waiting to be printed. The paper attracts the negatively charged toner particles from the drum.
In the ________ step of a laser printer printing a page, heat and pressure are used to fuse the toner to the paper.
State several user input devices.
Pointing devices
Mechanical Mouse
Optical Mouse
Game Controller
Light pens
Graphics tablets & Touch Screens
Keyboards consist of a number of switches and a keyboard controller. The keyboard controller is built into the keyboard. When a key is pushed, a signal called a ____________ is sent to the controller. A different signal is sent when the key is released. They allow keys to be used in combination.
Scan Code
A mouse is the best known pointer device.
As the ______ is moved across the surface, the roller ball protruding from the bottom also moves. Two wheels, mounted at right angles from each other, touch the roller ball and move with it. These wheels are called encoders. As the encoders move, they generate a series of pulses. The number of pulses corresponds to the distance that it has moved.
One encoder records the right-left movement and the other encoder records the up-down movement. The pulses are sent to a program in the computer to interpret the current location of the mouse.
Some encoders use a tiny light and sensor to create the pulses while others use a tiny mechanical switch.
Desktop game pointing devices and trackballs work similarly.
A _________ is pointed at a screen to identify a position on the screen. By moving it around the screen, a cursor can be made to follow it. It can be used to point to a target, such as a control button on the screen, and can be used as a drawing tool. It is not actually capable of telling the system its position. Instead, the software program that is used with it rapidly generates pixels of light on the display screen at known locations in the area where it is believed to be pointing.
Light Pen
The light pen has a photo detector that can respond to the point of light on the screen, so when the point on the screen that corresponds to the light pen is lit; the light pen is activated, which notifies the program that the current location is correct.
Graphics tablets use a variety of techniques, including pressure sensitive sensors, optical sensors, magnetic sensors and capacitive sensors to determine the location of a pen on the pad. They are particularly suited for drawing.
A similar mechanism is used for the touch pads commonly found on laptop computers.
Touch screens provide a capability similar to those of graphics tablets, but with the sensing mechanism attached directly to the display screen, allowing the user to point directly to an object on the screen.
__________ are the primary means used to input paper images.
State the Three primary types of scanners: (test question)
Flatbed scanners
Sheet-fed scanners and
Hand-held scanners
The resolution of a scanner is similar to that of printers, approximately 600 - 2400 points per inch.
The mechanism of a _____________ consists of a light source and a row of light sensors. As the light is reflected from individual points on the page, it is received by the light sensors and translated to digital signals that correspond to the brightness of each point. Color filters can be used to produce color images, either by providing multiple sensors or by scanning the image three times with a separate color filter for each pass.
The resolution of a scanner is similar to that of printers, approximately 600 - 2400 points per inch.
From the perspective of a computer, a network is simply another I/O device, a device that, like a disk, offers input to applications on the computer and receives output from applications on the computer.
(Test Question) True
Like other I/O devices, there is a ___________ that handles the physical characteristics of the connection and one or more I/O drivers that manage and steer input data, output data and interrupts
network interface card (NIC)
The ________ is responsible for the electrical signals that connect the computer to the network, directly or through a communication channel. It is also responsible for the protocols, implemented in hardware, that define the specific rules of communication for the network. These protocols are called medium access control protocols (MAC protocols).
network interface card (NIC)
Every NIC and network device has a unique physical address that is burned into the device at the factory. This physical address is referred to as the ________ address.
MAC Address
The NIC is also responsible for the protocols, implemented in hardware, that define the specific rules of communication for the network. These protocols are called ______.
medium access control protocols (MAC protocols).