实例1：
@echo off
echo the name of the bat file is
%0
echo the first vars of the bat file is
%1
call:function1
call:function2
call:function2
call:function3
call:function4 robin
goto LabelEnd
echo this should not be seen
:LabelEnd
exit /b 0
:function1
echo:1
exit /b 0
:function2
echo:2
exit /b 0
:function3
echo:3
exit /b 0
:function4
echo:
函数名是 %0
echo:the first vars of function is
%1
exit /b 0
注意1：exit的使用。
Quits the CMD.EXE program (command interpreter) or the current batch script.
EXIT [/B] [exitCode]
/B specifies to exit the current batch script instead of
CMD.EXE. If executed from outside a batch script, it
will quit CMD.EXE
exitCode specifies a numeric number. if /B is specified, sets
ERRORLEVEL that number. If quitting CMD.EXE, sets the process
exit code with that number.
exitCode可以通过系统变量ERRORLEVEL取得
注意2：函数和标签的定义一样，
只是调用方式不一样。函数用call:+函数名的形式，比如call:function1。
标签使用goto LabelEnd的形式。函数还有可以
传递参数比如：call:function4 robin，而标签不行。
函数调用有
返回值，而标签没有。