Abstract
With the increase of social material wealth, safety and guarding against theft have become social problems. Meanwhile, the ordinary mechanical locks are hard to meet the need of social management and prevention of burglary. At present what in market universal use is the mechanical lock，its confidentiality is poor、security is low、easy to copy or be used by other people、easy to damage and other issues.
To meet people's requirement of the use of locks, to increase the security, the code locks which use password instead of key emerge as the times require. Moreover they have many advantages, for example they are more convenient and many password. If the structure is simple, password volume of transactions through easy means to try to unlock the code, the safety factor is not high enough. But electronic password lock with password great quantity, Password mainly by a controller chip AT89S51 through programming to achieve their specific function.Programming with the password change for the sake of change greatly improving security.
The use of keystroke input SCM software decoder programs, the program can achieve better identification password, the password wrong alarm function meet basic password lock function.
Key word: The monolithic integrated circuit (AT89S51), Password lock，alarm system
