NAME
    CurrentDir -- Make a directory lock the current directory
SYNOPSIS
    oldLock = CurrentDir( lock )
    D0                    D1
    BPTR CurrentDir(BPTR)
FUNCTION
    CurrentDir() causes a directory associated with a lock to be made
    the current directory.  The old current directory lock is returned.
    A value of zero is a valid result here, this 0 lock represents the
    root of file system that you booted from.
    Any call that has to open() or lock() files (etc) requires that
    the current directory be a valid lock or 0.
INPUTS
    lock - BCPL pointer to a lock
RESULTS
    oldLock - BCPL pointer to a lock
SEE ALSO
    lock(), unlock(), open(), duplock()