tYpE oF PeNdRiVe

HiStOrY

First commercial product

Trek Technology and IBM began selling the first USB flash drives commercially in 2000. Trek Technology sold a model under the brand name "ThumbDrive", and IBM marketed the first such drives in North America with its product named the "DiskOnKey," which was developed and manufactured by M-Systems.[20] IBM's USB flash drive became available on December 15, 2000,[21] and had a storage capacity of 8 MB, more than five times the capacity of the then-common floppy disks.

In 2000, Lexar introduced a Compact Flash (CF) card with a USB connection, and a companion card read/writer and USB cable that eliminated the need for a USB hub.[citation needed]
Second generation

Modern flash drives have USB 2.0 connectivity. However, they do not currently use the full 480 Mbit/s (60 MB/s) which the USB 2.0 Hi-Speed specification supports because of technical limitations inherent in NAND flash and the overhead required for USB data transfers (8-bit / 10-bit encoding and protocol)[22]. The fastest drives currently available use a dual channel controller, although they still fall considerably short of the transfer rate possible from a current generation hard disk, or the maximum high speed USB throughput.

File transfer speeds vary considerably. Speeds may be given in Mbyte per second, Mbit per second or optical drive multipliers such as "180X" (180 times 150 KiB per second). Typical fast drives claim to read at up to 30 megabytes/s (MB/s) and write at about half that speed. This is about 20 times faster than USB 1.1 "full speed" devices, which are limited to a maximum speed of 12 Mbit/s (1 MB/s with overhead)[23].
Third generation

Like USB 2.0 before it, USB 3.0 offers dramatically improved data transfer rates compared to its predecessor. USB 3.0 was announced in late 2008, but consumer devices were not available until the beginning of 2010. The USB 3.0 interface specifies transfer rates up to 5 Gbit/s (625 MB/s), compared to USB 2.0's 480 Mbit/s (60 MB/s). All USB 3.0 devices are backward compatible with USB 2.0 ports. Computers with USB 3.0 ports are becoming very popular and common. Many newer laptops and desktops have at least one such port. USB 3.0 port expansion cards are available to upgrade older systems, and many newer motherboards feature two or more USB 3.0 jacks. Even though the USB 3.0 interface allows extremely high data transfer speeds, as of 2011 most USB 3.0 flash drives do not utilize the full speed of the USB 3.0 interface due to limitations of their memory controllers (though some four channel memory controllers are now coming to market)..

Anti Virus

HiStOrY

Most of the computer viruses written in the early and mid-1980s were limited to self-reproduction and had no specific damage routine built into the code.[3] That changed when more and more programmers became acquainted with virus programming and created viruses that manipulated or even destroyed data on infected computers.
There are competing claims for the innovator of the first antivirus product. Possibly the first publicly documented removal of a computer virus in the wild was performed by Bernd Fix in 1987.[4][5] There were also two antivirus applications for the Atari ST platform developed in 1987. The first one was G Data [6] and second was UVK 2000.[7]
Fred Cohen, who published one of the first academic papers on computer viruses in 1984,[8]began to develop strategies for antivirus software in 1988[9] that were picked up and continued by later antivirus software developers. In 1987, he published a demonstration that there is no algorithm that can perfectly detect all possible viruses.[10]
In 1987 the first two heuristic antivirus utilities were released: Flushot Plus by Ross Greenberg and Anti4us by Erwin Lanting.[citation needed]
Also in 1988 a mailing list named VIRUS-L[11] was started on the BITNET/EARN network where new viruses and the possibilities of detecting and eliminating viruses were discussed. Some members of this mailing list like John McAfee or Eugene Kaspersky later founded software companies that developed and sold commercial antivirus software.
Before internet connectivity was widespread, viruses were typically spread by infected floppy disks. Antivirus software came into use, but was updated relatively infrequently. During this time, virus checkers essentially had to check executable files and the boot sectors of floppy disks and hard disks. However, as internet usage became common, viruses began to spread online.[12]
Over the years it has become necessary for antivirus software to check an increasing variety of files, rather than just executables, for several reasons:
Powerful macros used in word processor applications, such as Microsoft Word, presented a risk. Virus writers could use the macros to write viruses embedded within documents. This meant that computers could now also be at risk from infection by opening documents with hidden attached macros.[13]
The possibility of embedding executable objects inside otherwise non-executable file formats can make opening those files a risk.[14]
Later email programs, in particular Microsoft's Outlook Express and Outlook, were vulnerable to viruses embedded in the email body itself. A user's computer could be infected by just opening or previewing a message.[15]
As always-on broadband connections became the norm, and more and more viruses were released, it became essential to update virus checkers more and more frequently. Even then, a new zero-day virus could become widespread before antivirus companies released an update to protect against it.

\cOmPuTeR GeNeRaTiOn

INPUT DEVICE 

OUTPUT DEVICE

                                                 

                                                                     SpEaKeR


Computer speakers, or multimedia speakers were introduced by altec lansing in 1990.[1]They are speakers external to a computer, that disable the lower fidelity built-in speaker. They often have a low-power internal amplifier. The standard audio connection is a 3.5 mm (approximately 1/8 inch) stereo phone connector often color-coded lime green (following thePC 99 standard) for computer sound cards. A few use an RCA connector for input. There are also USB speakers which are powered from the 5 volts at 500 milliamps provided by the USB port, allowing about 2.5 watts of output power.
Computer speakers range widely in quality and in price. The computer speakers typically packaged with computer systems are small, plastic, and have mediocre sound quality. Some computer speakers have equalization features such as bass and treble controls.

The internal amplifiers require an external power source, usually an AC adapter. More sophisticated computer speakers can have a subwoofer unit, to enhance bass output, and these units usually include the power amplifiers both for the bass speaker, and the small satellite speakers.
Some computer displays have rather basic speakers built-in. Laptops come with integrated speakers. Restricted space available in laptops means these speakers usually produce low-quality sound.
For some users, a lead connecting computer sound output to an existing stereo system is practical. This normally yields much better results than small low-cost computer speakers. Computer speakers can also serve as an economy amplifier for MP3 player use for those who wish to not use headphones, although some models of computer speakers have headphone jacks of their own