Computer Note

Advantages of using hard disk It is very fast to access data. That is, the access speed is very high. Data can be read directly from any part of the hard disk (random access). It has large storage capacity You can have two hard disks in a machine, one can act as a mirror of the other and create a back up copy.

Disadvantages of using hard disk Hard disks may crash thereby leading to loss of data. It is therefore, a wise decision to backup data regularly. The disk is fixed inside the computer and cannot easily be transferred to another computer.

Parts of a hard disk www.computer.howstuffswork.com Write a comprehensive note on how hds work. www.computer.howstuffswork.com

Floppy disks Microcomputers accept 3.5 inch floppy disks. They hold 1.44 MB of data (enough to store about 350 pages of A4 text). A floppy disk needs to be formatted before it can be used but most disks are already formatted for PC's. www.computer.howstuffswork.com

Magnetic Tapes Any application which requires extremely large storage capacity where speed of access is not an issue. Uses serial access for reading and writing. Used for backups of file servers for computer networks. Used in a variety of batch processing applications such as reading of bank cheques, payroll processing and general stock control. Conventional tape comes in reels up to 4600 feet long. Magnetic tapes stored in racks

Tape Cartridges Tape is also available in cartridges. Tape cartridges are frequently used for backing up hard discs on microcomputers. Tape streamers can be scheduled to make backups at night. Data access is slow. It takes a while for a computer to find data if it is in the middle of a tape. A tape cartridge

Magnetic Tape is now mainly used as a backup medium Magnetic Tape is now mainly used as a backup medium. It is a cheap medium for backing up hard discs on both microcomputers and mainframes.

Optical Storage Media E.g. CD, DVD CDs tend to be used for large files (but smaller than 1Gb) which are too big for a floppy disc to hold such as music and animation. About 700mb DVDs are used to hold very large files (several Gb) such as movie films. Both CDs and DVDs are portable i.e. they can be transported from one computer to another. About 4.7Gb DVD stands for Digital Versatile Disc

CDs and DVDs Used for applications which require the prevention of deletion of data, accidental or otherwise. CDs are used by software companies for distributing software programs and data; Used by Music companies for distributing music albums DVDs are used by book publishers for distributing encyclopaedias, reference books etc and by film distributors.

CD-R/DVD-R CDs allow for single burning of data, e.g. – recording of music downloads from the Internet, recording of music from MP3 format, recording of data for archiving or backup purposes. DVDs – recording of film movies and television programs.

CD RW/DVD RW They are used for storing applications which require updating They have the feature of writing over old data. They are not suitable for music recording but is very useful for keeping generations of files. DVDs have between five and ten times the capacity of CDs.

DVD RAM Housed in a cartridge. Used in video recorders, camcorders and computer memory.

A DVD-RAM disc can be identified by many small rectangles distributed on the surface of the data carrier. These rectangles constitute the hard (factory originated) sectoring of the DVD-RAM

HD DVD Used in video recorders and computer memory as well as games consoles It is a main rival to blu-ray. HD DVD High-Definition/Density DVD) is a defunct high-density optical disc format for storing data and high-definition video.

...HD DVD... Media type: High-density optical disc Capacity: 15GB (single layer) 30 GB (dual layer) Usage: Data storage, including high-definition video.

Blu-ray Used in video recorders and computer memory as well as games consoles. It is the largest storage capacity of optical media.

Blu Ray Disc Media type: High-density optical disc Capacity 25 to 50 GB (single-layer) 50 to 100 GB (dual-layer) Usage Data: storage High-definition video High-definition audio and 3D

Solid State Backing Storage The most compact form of storage device It is used as removable storage. More robust than other forms of storage. More expensive than other forms of storage It can be easily written to and updated.

Examples of Solid state Storage 1. MEMORY STICKS OR PEN DRIVES Can store up to 8 GB or more. Used to transport files from computer to computer. It can also be used for data backup.

2. Flash memory Flash memory is a non-volatile form of memory chip - the data is still stored when the power is turned off. Data stored on flash memory chips can be erased and the memory can be re-used. This has made them useful in digital cameras, mp3 players, palm-top computers and mobile phones. Many computers now have card slots where flash memory cards can be inserted and read in a similar way to a floppy disc. Alternatively, Flash memory card readers can be connected to a computer to read and write to cards. A flash memory card that can be used (for example) in a digital camera. Flash memory cards are also used in flash drives (also called memory sticks, USB sticks, pen drives, thumb drives etc). The drive is connected to a USB drive on a computer and acts as a portable backing store.

Assignment Write short notes on the following removable media: Zip Jaz Assignment: 1. State the differences between internal storage and backing storage 2. State the advantage of a. internal memory over hard disc b. Hard disc over internal memory 3. When data is no longer required it may be archived ... What is data archiving? Ans: kept in long-term storage. 4. True or false. RAM allows for large data storage…….. 5. What does each stand for? CD-R, CD-RW, DVD, CD-ROM 6. Data is written unto Cds and DVDs using ______