pusofalse

只要明白set /a的特性就能简洁明了的解答此题了。

If you use any of the logical or modulus operators, you will need to
enclose the expression string in quotes.  Any non-numeric strings in the
expression are treated as environment variable names whose values are
converted to numbers before using them.  If an environment variable name
is specified but is not defined in the current environment, then a value
of zero is used.  This allows you to do arithmetic with environment
variable values without having to type all those % signs to get their
values. 
复制代码

pusofalse

@echo off
Set "a=%random%" & set "b=%random%"
echo %a% %b%
set /a b=%a%,a=%b%
echo %a% %b%
pause
Set "a=%random%" & set "b=%random%"
echo %a% %b%
set /a b=a,a=b
echo %a% %b%
pause
复制代码

希望可以通过如上代码了解到set /a的特性。