INFO: Processes Maintain Only One Current Directory

Processes under Microsoft Windows NT, Windows 2000, or Windows XP maintain only one current directory. Under MS-DOS or OS/2, a process will maintain a current directory for each drive.

For example, if you do the following:

1. Set the current drive to be drive C and set the current directory to be \MAINC\MAINSUBC.
2. Change the current drive to be drive D and set the current directory to be \MAIND\MAINSUBD.

When you reset the current drive to drive C, the current directory will be the original directory: \MAINC\MAINSUBC.

MS-DOS and OS/2 use a current directory structure (CDS) to maintain this information. The memory for this structure is allocated at boot time, and is set by the LASTDRIVE= line in the CONFIG.SYS file. For example, if you set LASTDRIVE=Z, you will have 26 entries in the CDS and will be able to track 26 current directories.

Windows NT, Windows 2000, or Windows XP by default allows a process to track only one current directory--the one for the current drive--because the underlying operating system does not use drive letters; it always uses fully-qualified names such as: The Win32 subsystem maintains drive letters by setting up symbolic links such as: (Partitions are 1-based while hard disks are 0-based because Partition0 refers to the entire physical device, which is the "file" that FDISK opens to do its work.) Therefore, when you do SetCurrentDirectory("c:\tmp\sub"), the Win32 subsystem translates that to "\??\c:\tmp\sub", "...".

As far as Windows NT, Windows 2000, or Windows XP is concerned, there are no "drives," there is one object name space.

CMD.EXE maintains a private current directory for each drive it has touched and uses environment variables to associate a current directory with each drive.