Development of Computers

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Development of Computers The earliest known device to record computations was the abacus. It dates back to ancient times and was invented by the Chinese. Ten beads were strung onto wires attached to a frame. Addition and subtraction were read from the final positions of the beads. It was considered the first manual tool used in calculating answers to problems that provided information and in a primitive way storing the results. Abacus Mechanical Clock During the Middle Ages the first closed system in terms of calculating information was invented by use of a mechanical clock. The parts of the clock calculated the time of day. The time was displayed through the position of two hands on its face. The inventor pre-programmed the clock instructions through the manner in which the pull of the weights and the swing of the pendulum with the movement of the gears established the position of the hands on the clock face. Mathematics John Napier (Scotsman mid 1600s) discovered logarith

Optical disks

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 Optical disks

The Compact Disc
or CD for short, is an optical disc used to store digital data. It was originally developed to store and play back sound recordings only, but the format was later adapted for storage of data (CD-ROM), write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Discs (VCD), Super Video Compact Discs (SVCD), Photo CD, Picture CD, CD-i, and Enhanced CD. Audio CD's and audio players have been commercially available since October 1982. Have a storage capacity of 700MB or 80 minutes of continuous play.
kcse computer studies notes
Compact Disk

DVD/Digital Versatile/Video Disk 


Is an optical disc storage format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995, DVDs offer higher storage capacity than Compact Discs while having the same dimensions: Have a storage capacity of 4.7 GB or 2 hours of continuous play, up to 20 GB.

The modern DVDs are called a Blu-Ray Disk and HD DVD- In 2006; two new formats called HD DVD and Blu-ray Disc were released as the successor to DVD. HD DVD competed unsuccessfully with Blu-ray Disc in the format war of 2006–2008. A dual layer HD (high definition) DVD can store up to 30GB and a dual layer Blu-ray disc can hold up to 50GB.
KCSE COMPUTER STUDIES
HD DVD

KCSE COMPUTER STUDIES
BLU RAY DISK

 Optical tape 

Is a medium for optical storage generally consisting of a long and narrow strip of plastic on to which patterns can be written and from which the patterns can be read back. It can host at least 100 MB of data. Mostly used by cameras to store images, sounds and data.
KCSE COMPUTER NOTES
OPTICAL TAPE


Optical Cards

Optical memory cards use a technology similar to the one used for music CDs or CD ROMs. A panel of the "gold colored" laser sensitive material is laminated in the card and is used to store the information. Can store from 4 - 6.6 MB
KCSE COMPUTER NOTES
OPTICAL CARDS

 Flash disks

A USB flash drive is a data storage device that includes flash memory with an integrated Universal (USB) interface. USB flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g. As of September 2011 drives of 256 gigabytes (GB) are available. Storage capacities as large as 2 terabytes are planned, with steady improvements in size and price per capacity expected.
KCSE COMPUTER STUDIES
FLASH DISK

 Memory card

A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players and video game consoles. They are small, re-recordable, and able to retain data without power. Their storage capacities range from 32MB up to 2TB (terabytes). Memory cards are classified according to physical sizes, storage capacity and speed classes called SD- Secure Digital this is a non-volatile memory card format for use in portable devices. There is the Full SD, Mini SD and Micro SD.
KCSE COMPUTER STUDIES
MEMORY CARDS
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