Trong hầu hết trường hợp, PDA được sử dụng như một phương tiện thuận tiện truy cập dữ liệu thường cư trú trên máy tính. Dữ liệu được tạo ra trên một máy tính có thể được sao chép vào PDA đồng hành của nó, và ngược lại dữ liệu được tạo ra trên một PDA có thể được | Chapter 13 Viruses and the Losers Who Write Them 211 Brain the first virus In Pakistan Basit Farooq Alvi and Amjad Farooq Alvi ran a computer store called Brain Computer Services. They soon discovered that a floppy disk contained computer instructions that were executed when the computer was first turned on. Basit and Amjad used this knowledge for their own purposes and created computer instructions that would change the label of floppy disks in the computer to C Brain. The instructions would make a copy of themselves onto other floppy disks that were inserted into the floppy-disk drive. Brain did nothing other than change a floppy s label and copy itself to other floppies but that was sufficient to cause trouble. People continued to do what they had been doing for a few years exchanging computer programs and files using nearly the only available means circulating them on floppy disks. At first no one noticed that some of these floppies had a stowaway on board an unwanted passenger with a single although relatively benign purpose. In 1987 users at the University of Delaware began noticing that the labels on some of their floppy disks were mysteriously being changed to C Brain. The Brain virus had made its way from central Asia to North America and doubtless to the other continents of the world. Atari 800 a Tandy TRS-80 fondly known as the Trash 80 among the Rubik s Cube generation of computer users a Texas Instruments TI-99 4 a Commodore 64 or an Apple II. For the first time computer hobbyists and other curious types could purchase a fully functioning computer system for a relatively modest price. People were writing and trading programs like crazy giving one another copies of their programs pictures and data files using whatever portable storage medium their brand of computer used. The Trash-80 used cassette tapes others used floppy disks that you could actually flop. Computer hobbyists and tinkerers were exchanging computer files like school children share colds.
