Introduction to Computing

1. Introduction to Computing Slides By ADEELA MUSTAFA

2. Storage(7th –Chapter) What Is Storage Storageholds data, instructions, and information for future use. Every computer stores system software and application software. To start up, a computer locates an operating system (system software) in storage, usually a hard disk, and loads it into memory (RAM). When a user issues a command to start application software, such as a word processing program or a Web browser, the operating system locates the program in storage, such as on a hard disk or optical disc, and loads it into memory (RAM).

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4. Storage Storage Medium A storage medium(media is the plural), also called secondary storage, is the physical material on which a computer keeps data, instructions, and information. Examples of storage media are hard disks, solid state drives, memory cards, USB flash drives, ExpressCard modules, optical discs, smart cards, magnetic stripe cards, and microfilm. Cloud storage is another storage option, in which the actual storage media used is transparent to the user. Figure 7-1 shows a variety of storage options. Memory (RAM), by contrast, typically consists of one or more chips on the motherboard or some other circuit board in the computer.

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6. Storage Capacity Capacityis the number of bytes (characters) a storage medium can hold. Figure 7-2 identifies the terms manufacturers use to define the capacity of storage media. For example, a reasonably priced USB flash drive can store up to 4 GB of data (approximately four billion bytes) and a typical hard disk has 320 GB (approximately 320 billion bytes) of storage capacity. Items on a storage medium remain intact even when power is removed from the computer.

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8. Storage The speed of storage devices and memory is defined by access time. Access time measures (1) the amount of time it takes a storage device to locate an item on a storage medium or (2) the time required to deliver an item from memory to the processor. The access time of storage devices is slow, compared with the access time of memory. Memory (chips) accesses items in billionths of a second (nanoseconds). Storage devices, by contrast, access items in thousandths of a second (milliseconds) or millionths of a second (microseconds). Some manufacturers state a storage device’s transfer ratebecause it affects access time. Transfer rate is the speed with which data, instructions, and information transfer to and from a device. Transfer rates for storage are stated in KBps(kilobytes per second), MBps(megabytes per second), and GBps(gigabytes per second).

9. Storage Access Speed of Different Kind Of Devices…

10. Storage Hard Disks A hard disk, also called a hard disk drive or hard drive, is a storage device that contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information. Depending on how the magnetic particles are aligned, they represent either a 0 bit or a 1 bit. The system unit on most desktop and notebook computers contains at least one hard disk. The entire device is enclosed in an airtight, sealed case to protect it from contamination. A hard disk that is mounted inside the system unit sometimes is called a fixed disk because it is not portable. The term portablemeans you can remove the medium from one computer and carry it to another computer. Current personal computer hard disks have storage capacities from 160 GB to 2 TBand more.

11. Storage The hard disk in a desktop personal computer is enclosed inside an airtight, sealed caseinside the system unit. (In this and other hard disk photos in the book, the top plate is removed from the hard disk for illustration purposes).

12. Storage Traditionally, hard disks stored data using longitudinal recording, which aligned the magnetic particles horizontally around the surface of the disk. With perpendicular recording, by contrast, hard disks align the magnetic particles vertically, or perpendicular to the disk’s surface, making much greater storage capacitiespossible. Figure 7-6 shows the difference between longitudinal and perpendicular recording. Experts estimate that hard disks using perpendicular recording provide storage capacities about 10 times greater than disks that use longitudinal recording.

13. Storage Characteristics of a Hard Disk Characteristics of a hard disk include its capacity, platters, read/write heads, cylinders, sectors and tracks, revolutions per minute, transfer rate, and access time. A platteris made of aluminum, glass, or ceramic and is coated with an alloy material that allows items to be recorded magneticallyon its surface. A trackis a narrow recording band that forms a full circle on the surface of the disk. The disk’s storage locations consist of pie-shaped sections, which break the tracks into small arcs called sectors. On a hard disk, a sector typically stores up to 512 bytes of data. A clusteris the smallestunit of disk space that stores data and information. Each cluster, also called an allocation unit of two to eight sectors (the number varies depending on the operating system).

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17. Storage How Hard-Disk Work’s

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20. Storage RAID (redundant array of independent disks) Some personal computer manufacturers provide a hard disk configuration that connects multiple smaller disks into a single unit that acts like a single large hard disk. A group of two or more integrated hard disks is called a RAID. External and Removable Hard Disks Aseparatefreestandinghard disk that connects with a cable to a USB port or FireWireport on the system unit or communicates wirelessly. Although the transfer rate of external and removable hard disks usually is slowerthan that of internal hard disks, they do offer many advantagesover internal hard disks (fixed disks).

21. Storage (1) Transport a large number of files. (2) Back up important files or an entire internal hard disk (several external hard disk models allow you to back up simply by pushing a button on the disk). (3) Easily store large audio and video files. (4) Secure your data; for example, at the end of a work session, remove the hard disk and lock it up, leaving no data in the computer. (5) Add storage space to a notebook computer, including netbooks and Tablet PCs. (6) Add storage space to a desktop computer without having to open the system unit or connect to a network

22. Storage SATA (Serial Advanced Technology Attachment) uses serial signals to transfer data, instructions, and information. The primary advantage of SATA interfaces is their cables are thinner, longer, more flexible, and less susceptible to interference than cables used by hard disks that use parallel signals. SATA interfaces have data transfer rates of up to 300 MBpsand higher. In addition to hard disks, SATA interfaces support connections to optical disc drives. External disks can use the eSATA(external SATA) interface, which is much faster than USBand FireWire.

23. Storage USB Flash Drives AUSB flash-drive, sometimes called a thumb drive, is a flash memory storage device that plugs in a USB port on a computer or mobile devise. USB flash drives are convenient for mobile users because they are small and lightweight enough to be transported on a keychain or in a pocket. USB flash drives have data transfer rates of about 12 MBps. Some USB flash drives include fingerprint readers, restricting access to authenticated users.

24. Storage Solid State Drives A solid state drive (SSD) is a storage device that typically uses flash memory to store data, instructions, and information. SSDs are used in all types of computers includingservers, desktop computers, and mobile computers and devices such as portable media players and digital video cameras. Storage capacities of current SSDs range from 16 GB to 256 GB and more. SSDs have several advantages over magnetic hard disks.

25. Storage (1) Access times of SSDs are about 0.1 ms, which is more than 80 times faster than a hard disk. (2) Transfer rates of SSDs are faster than comparable hard disks. For example, SSD transfer rates range from 80 to 100 MBps, while transfer rates of a typical 2.5-inch hard disk is about 60 MBps. (3)SSDs generate less heat and consume less power than hard disks. (4)Manufacturers claim that SSDs will last more than 50 years, which is much greater than the 3 to 5 year hard disk stated lifespan.

26. Storage Memory Cards Memory cards enable mobile users easily to transport digital photos, music, or files to and from mobile devices and computers or other devices. A memory card is a removable flash memory device, usually no bigger than 1.5 inches in height or width, that you insert and remove from a slot in a computer, mobile device, or card reader/writer. Common types of memory cards include CompactFlash (CF), Secure Digital (SD), Secure Digital High Capacity (SDHC), microSD, micro SDHC, xD Picture Card, Memory Stick, and Memory Stick Micro (M2).

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29. Storage Cloud Storage Some users choose cloud storage instead of storing data locally on a hard disk or other media. Cloud storage is an Internet service that provides storage to computer users Some provide storage for specific types of files, such as photos or e-mail messages, whereas others store any type of file. Many cloud storage providers offer additional services such as encryption, passwords, Web applications, and Web services.

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31. Storage Users subscribe to cloud storage for a variety of reasons: (1)To access files on the Internet from any computer or device that has Internet access. (2)To store large audio, video, and graphics files on the Internet instantaneously, instead of spending time downloading to a local hard disk or other media. (3)To allow others to access their files on the Internet so that others can listen to an audio file, watch a video clip, or view a photo — instead of e-mailing the file to them. (4)To view time-critical data and images immediately while away from the main office or location; for example, doctors can view X-ray images from another hospital, home, or office, or while on vacation. (5)To store offsite backups of data. (6)To provide data center functions, relieving enterprises of this task.

32. Storage Optical Discs An optical disc is a type of storage media that consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser. Optical discs used in personal computers are 4.75 inches in diameter and less than one- twentieth of an inch thick. Smaller computers, game consoles, and mobile devices, often use mini discsthat have a diameter of 3 inches or less. With some discs, you can read and/or write on one side only. Manufacturers usually place a silk-screened label on the top layer of these single-sided discs. You insert a single-sided disc in the drive with the label side up. Other discs are double-sided. Simply remove the disc from the drive, flip it over, and reinsert it in the drive to use the other side of the disc. Double-sided discs often have no label.

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34. Storage Hard-Drive Optical-Disk Solid State Drive

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36. End Thank You All (have a nice day)