about the “OLDOLDPWD”

[lumianshuo@DELL]

Hello , when I use the cd and dirs. Sometimes I need the last‘OLDPWD is cur PWD 
or not .
Alright I can record the var at the begin. But if can I judge this by a tool 
that shell given? i.e. have the shell save the “last” OLDPWD ? If have , where 
have it saved?