Tandy 1000 Programmer's Reference Manual page 107

Chapter
1 I System
Calls
ChDir
Change the Current
Directory
Function Call 3BH
Sets the current directory to the directory specified.
If
any member of the specified pathname does not exist, then
the current directory is unchanged.
Entry Conditions:
AH
=
3BH
DS:DX
=
pointer to ASCZIZ pathname
Exit Conditions:
Carry set:
AX
=
error code
Carry not set:
No error.
Error Returns:
A = 3
Path not found. The path specified either indicated a
file or the path was invalid.
Example:
C h D i r
eq" 38H
I d s d x , p a t h n a m e
mov
a h , C h D i r
i n t
21
H
105