@echo off
SET str1 = String1
SET str2 = String2
if %str1%==String1 (echo "The value of variable String1") else (echo "Unknown value")
if %str2%==String3 (echo "The value of variable c is String3") else (echo "Unknown value")
if %var1%=="Yes" echo Var1
if %var1%=="Yes" (
echo Var1
)