各种用C语言实现的延时函数，均已经过调试修改，延时较为准确，分微秒级、毫秒级和秒级延时。注：将里面的reg52.h的头文件复制进自己的keil头文件库中才能运行，里面有自定义的内容（自定义部分有标注），编译环境为keil uvision-Various delay using C language functions have been modified after commissioning, the delay is more accurate, sub-microsecond, millisecond and second-level latency. Note: The inside of the reg52.h header files copied into its own header file keil library in order to run, which has a custom content (part of a custom label), the compiler environment keil uvision