unix的基础学习源码，登录客户端显示服务器段的相关内容-the basis for learning unix source, the client displays the server log related content section

这是一小段PC喇叭发声源码,它显示如何在LINUX应用程序中直接访问硬件端口.-A piece of source codes which implement beep in a application which can direct access hardware io port.