Logical operators ("and", "or") in DOS batch

How would you implement logical operators in DOS Batch files?

You can do and with nested conditions:

if %age% geq 2 (
    if %age% leq 12 (
        set class=child
    )
)

or:

if %age% geq 2 if %age% leq 12 set class=child

You can do or with a separate variable:

set res=F
if %hour% leq 6 set res=T
if %hour% geq 22 set res=T
if "%res%"=="T" (
    set state=asleep
)

The IF statement does not support logical operators AND and OR. Cascading IF statements make an implicit conjunction:

IF Exist File1.Dat IF Exist File2.Dat GOTO FILE12_EXIST_LABEL

If File1.Dat and File2.Dat exist then jump to the label FILE12_EXIST_LABEL.

See also: IF /?

De Morgan's laws allow us to convert disjunctions ("OR") into logical equivalents using only conjunctions ("AND") and negations ("NOT"). This means we can chain disjunctions ("OR") on to one line.

This means if name is "Yakko" or "Wakko" or "Dot", then echo "Warner brother or sister".

set warner=true
if not "%name%"=="Yakko" if not "%name%"=="Wakko" if not "%name%"=="Dot" set warner=false
if "%warner%"=="true" echo Warner brother or sister

This is another version of paxdiablo's "OR" example, but the conditions are chained on to one line. (Note that the opposite of leq is gtr, and the opposite of geq is lss.)

set res=true
if %hour% gtr 6 if %hour% lss 22 set res=false
if "%res%"=="true" set state=asleep