computer memory ,., .
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This document provides an overview of different storage types and devices in computer systems, including hard drives, floppy disks, and optical storage like CD/DVD. It categorizes storage by their operations, access methods, technologies, and hierarchies, explaining concepts such as online, near-online, and offline storage. Additionally, it discusses the performance metrics of storage devices, including capacity and access times.
computer memory ,., .
- 3. Hard Drive – storage RAM – memory Storage, also known as mass media or auxiliary storage, refers to the various media on which a computer system can store data. Storage devices hold programs and data in units called files. Memory is a temporary workplace where the computer transfers the contents of a file while it is being used.
- 4. Registers 2ns Cache (I, II, III) SRAM Volatile DRAM SDRAM Primary RAM (Semiconductor – chip). Main Memory Memory Types & Storage Devices EDRAM EDO FLASH RAM PROM Non-volatile ROM EPROM EEPROM Magnetic memory Secondary (Devices) Tape HD, Zip Disk FDD Optical Memory CD-ROM, CD-R, CD-RW DVD-ROM, DVD-R 5ms DVD- RW
- 5. Storage devices: Retain Are cheaper than memory Play Are data when the computer is turned off an important role during startup needed for output
- 17. Storage devices are categorized by: The type of operations they perform The method they use to access the information The technology they use Their location in the storage hierarchy Their capacity and speed
- 18. Tape Drive – sequential storage Floppy Disk Drive – random-access storage Hard Disk – random-access storage Sequential – Storage devices that read and write data in a serial (one after the other) fashion Random-Access – Storage devices that read and write data without going through a sequence of locations
- 19. Magnetic Storage Optical Storage – CD/DVD drive Magnetic – Storage devices use disks or tapes that are coated with magnetically sensitive material Optical – Storage devices that use laser beams to read patterns etched into plastic disks
- 20. The three levels of storage hierarchy are: Online storage – Also called primary storage, it is made up of the storage devices that are actively available to the computer system. User action is not required. Near-online storage – Also called secondary storage, it is not readily available to the computer system. The user performs an action, such as inserting a disk, to make it available. Offline storage – Also called tertiary storage or archival storage, it is not readily available to the computer system. Devices such as tape backup units store data for archival purposes. Slide 22
- 21. Floppy Disk Capacity – 720 KB to 1.44 MB Access Time – 100ms Hard Drive Capacity – Up to 80 GB Access Time – 6 to 12ms CD ROM / DVD Capacity – CD-ROM 650 MB; DVD 17 GB Access Time – 80 to 800ms A storage device’s performance is measured by: Capacity – The number of bytes of data that a device can hold Access Time – The amount of time, in milliseconds (ms), it takes the device to begin reading data
- 22. Platter Read/Write head Hard disks are high-speed, high-capacity storage devices. They contain metal disks called platters. They contain two or more stacked platters with read/write heads for each side. Hard disks can be divided into partitions to enable computers to work with more than one operating system.
- 24. Floppy Drive Zip Drive A disk or diskette is a portable storage medium. High-density floppy disks that are commonly used today store 1.44 MB of data. Disks work with a disk drive. Zip disks store up to 750 MB of data and are not downwardly compatible with floppy disks. Floppy Disk
- 25. CD-ROM stands for Compact Disc-Read Only Memory. CD-ROM drives can not write data to discs. They are capable of storing 650 MB of data. They are used for storing operating systems, large application programs, and multimedia programs.
- 27. CD-R Discs can be read and written to Discs can only be written to “once” CD-R drives are capable of reading and writing data CD-RW Discs can be read and written to Discs are erasable Discs can be written to many times CD-RW drives are capable of reading, writing, and erasing data
- 28. DVD stands for Digital Video Disc. DVD technology is similar to CDROM technology. DVDs are capable of storing up to 17GB of data. The data transfer rate of DVD drives is comparable to that of hard disk drives. DVD-R and DVD-RW drives have the ability to read/write data.
- 29. Solid state storage devices use nonvolatile memory chips to retain data. They do not have moving parts. They are small, lightweight, reliable, and portable.