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CSC 170 – Introduction toComputers and Their ApplicationsLecture #5 – Storage andInput/OutputStorage Basics Storage is a term used for the components of a digitaldevice designed to hold data permanently. A data storage system has two main components: astorage medium and a storage device– Storage medium – the hard drives, CDs, DVDs, flashdrives, solid state drives, and memory cards that containsdata– Storage device – the mechanical apparatus that records andretrieves data from a storage medium1

Storage Basics Each storage technology has its advantagesand disadvantages, so review its durability,dependability, speed, capacity, and cost beforebuying.Storage Basics - Durability– Durability is the resistance to damage fromhandling and environmental factors such asdust, humidity, heat, and cold.– Can be measured in lifespan or in writecycles (the number of times data can bewritten and revised).2

Storage Basics - Dependability– Dependability is being available when needed; notsubject to breakdown, malfunction, networkoutages, or service interruptions.– Can be measured by mean time between failures(MTBF is the time a device is expected to functionbefore failing).– Cloud storage service dependability can bemeasured by uptime (the percent of time theservice is accessible).Storage Basics - Speed– Speed is the rate at which data can be storedor accessed. Faster is better.– Can be measured by data transfer rate (thenumber of megabytes per second that areread or written by the storage device).3

Storage Basics Capacity– The amount of data that can be stored,usually measured in gigabytes (GB) orterabytes (TB). Cost– The price of the storage device and media,usually expressed per gigabyte (GB).Storage Basics4

Magnetic Storage Technology Magnetic storage technology is used for desktop andlaptop hard disk drives, as well as the storage devicesused in enterprise computing installations and cloudservices.Magnetic Storage Technology Magnetic storage represents data by magnetizingmicroscopic particles on a disk or tape surface A hard disk drive contains one or more platters andtheir associated read-write heads A hard disk platter is a flat, rigid disk made ofaluminum or glass and coated with magnetic ironoxide particles A read-write head mechanism in the disk drivemagnetizes particles to write data, and senses theparticles’ polarities to read data5

Magnetic Storage Technology Before data is stored on a hard disk, particles on the disksurface are scattered in random patterns. The disk drive’s readwrite head orients them in a positive (north) or negative(south) direction to represent 0 and 1 bits, respectively.Magnetic Storage Technology Hard disk drive specifications include:– Access time – the average time it takes a computerto locate data on the storage medium and read it– Data transfer rate – the amount of data a storagedevice can move per second from the storagemedium to RAM6

Optical Storage Technology CD, DVD, and Blu-ray (BD) technologies areclassified as optical storage, which representsdata as microscopic light and dark spots on thedisc surface An optical drive contains a laser that directs abeam of light toward the underside of the disc Reflected light is collected by a lens andconverted into 0s and 1s that represent dataOptical Storage Technology A single optical drive typically handles CDs,DVDs, and Blu-ray discs, but the costs andcapacities of these discs vary– CD 650 MB 15 CD (compact disc): Designed to hold 74 minutes ofrecorded music, then adapted for computer storagewith capacity for 650 MB of data. Later improvementsin CD standards increased the capacity to 80 minutesof music or 700 MB of data.7

Optical Storage Technology–DVD 4.7 GB 25 DVD (digital video disc or digital versatile disc):Designed with the capacity to hold a feature-lengthfilm. A single-sided DVD offers 4.7 GB (4,700 MB) ofdata storage. A double-layer DVD has two recordablelayers on the same side and can store 8.5 GB of data.– Blu-ray 25 GB 50 Blu-ray (BD): Designed to hold high-definition 1080pvideo by offering 25 GB storage capacity. The nameBlu-ray is derived from the blue-violet colored laserused to read data. DVD technology uses a red laser;CD technology uses a near infrared laser.Optical Storage Technology Optical technologies are grouped into threecategories: read-only, recordable, and rewriteable– ROM. Read-only technology stores data permanently on adisc, which cannot be later added to or changed; canpotentially store data for 100 years.– R. Recordable technology uses a laser to change the colorin a dye laser sandwiched beneath the clear plastic discsurface; the laser creates dark spots that are read as pits.– RW. Rewritable technology uses phase change technologyto alter a crystal structure on the disc surface; altering thisstructure creates patterns of light and dark spots resemblingpits and lands.8

Solid State Storage Technology Solid state storage (sometimes called flashmemory) stores data in erasable, rewritablecircuitry, rather than on spinning disks orstreaming tape. Once the data is stored it is non-volatile,meaning the circuits retain data without anexternal power source.Solid State Storage Technology A memory card is a flat, solid state storage mediumcommonly used to transfer files from digital camerasand media players to computers.9

Solid State Storage Technology A solid state drive (SSD) is a package of flash memory thatcan be used as a substitute for a hard disk drive.A USB flash drive is a portable storage device that plugsdirectly into a computer’s system unit using a built-in USBconnector.35 cost per GBSSDs are widely used as the main storage device in smartphonesand tablet computers. Some laptops also include an SSD insteadof hard disk driveCloud Storage Remote storage is housed on an external device that can beaccessed from a networkRemote storage can also be available as an Internet service, inwhich case it is called cloud storage.Cloud storage is provided to individuals by services such asApple iCloud, Microsoft OneDrive, Google Drive, andDropbox.10

Cloud Storage Some cloudimplementations offer asynchronization featurethat automaticallyduplicates files storedon a local device byalso saving them in thecloud.Cloud Storage Security and privacy risks – the more placesyour data is stored and the more networks onwhich it travels, the more susceptible it becomesto intercepts from hackers and government spyingagencies. Service outages – when a cloud storage site hasan outage, all the data stored there becomestemporarily inaccessible. Discontinuation of service – some cloud storageproviders have closed down their services withlittle warning .11

Backup A backup is a copy of one or more files that is made in casethe originals become damaged or lostFiguring out what to backup is important; backing upeverything isn’t always practical– Operating system: The operating system is required tostart your device, but a backup copy might not run if itis unauthorized.– Software: Most devices are populated withpreinstalled software, and you’ve probablydownloaded and installed many additional apps. Ifthese are wiped out when a storage device fails, theprocess of downloading and reinstalling them can betime consuming.Backup– Data files: Your documents, photos, music,videos—all the goodies that you’ve created andgathered—can be difficult or impossible toreconstruct from scratch.– Settings, accounts, and profiles: How much timedid you spend customizing your home screen,entering contacts, choosing passwords, and settingpreferences for your favorite apps? No one wantsto have to do that all over again!12

Backup When deciding on what to back up, know what’simportant and ensure that current versions exist onmore than one storage device.Backup Tools you’ll need for backups:– Recovery drive (system repair disc) – contains parts of theOS necessary to boot your computer and diagnose systemproblems– Copy command – allows you to make copies of essentialfiles– File History – allows for automated data backup and filesynchronization to make copies of files from yourDocuments, Music, Picture, Pictures, and Videos folders– System image – Windows includes a disk image optioncalled System Image; a bit-for-bit copy of the data from allsectors of a hard disk13

Input/Output – Add-on Devices There are lots of options available for gadgets thataccompany your digital devicesExpansion Ports Many digital devices have ports in the systemunit for connecting cables and various add-ons;these ports are called expansion ports becausethey expand the options for input, output, andstorage. When you plug in a USB flash drive or insert amemory card, you are using an expansion port.14

Expansion PortsExpansion Ports If you want to connect more devices than theavailable number of USB ports, you can use a USBhub.15

Bluetooth A common wireless technology for connectingperipherals is Bluetooth. Bluetooth is a low-power technology, so it isideal for mobile devices that don’t have bigbatteries. Bluetooth is used to connect wireless headsetsto smartphones and is built into manysmartphones, tablets, laptops, and desktops.Device Drivers and Apps A device driver is software that helps aperipheral device establish communicationwith its host device. For example, the device driver for an HPprinter sets up data streams from RAM to theprinter and makes sure that the data isformatted in a way that the printer can work.16

Display Devices A computer display device that simply displaystext and images is classified as an outputdevice. Touchscreens, however, can be classified asboth input and output devices because theyaccept input and also display output. LCD (liquid crystal display) technologyproduces an image by filtering light through alayer of liquid crystal cells.Display Devices Factors that affect image quality are:– Screen size – the measurement in inches from onecorner of the screen diagonally across to the oppositecorner.– Response rate – the time it takes for one pixel tochange from black to white then back to black.– Dot pitch (dp) – the LED’s that form an image on thescreen are spaced in a grid; dp is the distance inmillimeters between like-colored LEDs.– Screen resolution – the number of horizontal andvertical pixels that a device displays on the screen.17

Display Devices Tablet computers,handheld devices, retailstore self-checkouts,and ATMs displayoutput and collect inputfrom a touchscreen. They can also display avirtual keyboard fordevices that are notconnected to a physicalkeyboard.Display Devices Display devices require graphics circuitry togenerate and transport the signals fordisplaying an image on the screen. One type of graphics circuitry, referred to asintegrated graphics, is built into a computer’ssystem board.18