Hi, do you mean a command line interface? There are a few in the AppStore. Those can be used to remote in to computers on your network. If you want to access the HD of your iPad you will need to jailbreak it first.
Head over to our Hacking Section for more information on jailbreaking and I strongly recommend you read ALL the sticky threads there - iPad Hacking
Unfortunately, the chances are you will not be able to jailbreak your device currently, unless you are extremely lucky and have left yourself on IOS version 5.1.1. IOS6 cannot currently be jailbroken and there is no way to revert back to a jailbreakable state unless you took precautions a very long time ago. Since you are only now discovering jailbreaking, the chances of that are almost zero.