Why do we use computer?

• ``Computer can do many things I can't do.'' Actually, a computer can only do what we human know exactly how to do.
• For example, the 4-color conjecture was solved by computer. But the steps of proof was designed by human.
• Don't treat a computer as a black box. Everything a computer does is programmed by human.
• Can computers eventually take over and control us human? Computational algorithms can never lead to understanding or consciousness (Penrose).
• So why do we use computer? (a) Speed, (b) reliability.

The Model of computation

• Control: how to implement a given task?
• Compute: $3 \times 5 = 15, 2 + 15=17$
• Program: a sequence of operations.
• Data: operands, intermediate results, final results.