Part 1 of Essay
About two hundred years before, the word "computer" started to appear in the dictionary. Some people even didn't know what is a computer. However, most of the people today not just knowing what is a computer, but understand how to use a computer. Therefore, computer become more and more popular and important to ....

Part 2 of Essay
.... For example, send a flood of coffee toward a personal computer. The hard disk of the computer could be endangered by the flood of coffee. Besides, human caretaker of computer system can cause as much as harm as any physical hazard. For example, a cashier in a bank can transfer some money from one of his customer's account to his own account. Nonetheless, the most dangerous thief are not those who work with computer every day, but youthful amateurs who experiment at night --- the hackers. The ....