Radio Shack TRS-80 Model II Reference Manual page 227

Technical Information
FILPTR
Get Pointers of a Currently Open File
(function code 58)
This routine provides information on any user file that is currently open.
Entry Conditions
A
=
58
(DE) =
Data Control Block
(DCB)
defined when file was opened.
Exit Conditions
NZ
=
Error occurred. Register A contains
TRSDOS
error code.
Z
=
No error. The following registers are set up:
B
=
Which dri ve contains the file (binary 0, I, 2, or 3)
C
=
Position of file in the diskette directory (binary 1-96)
User Notes
This routine is especially intended for use in conjunction with the
SVC RAMDIR.
After opening a file, the programmer may:
1. Use
FILPTR
to find out which drive contains the file and which directory record
contains the file's information.
2. Use
RAMDIR
to obtain pertinent information about that file (current file space
allocated/used, protection level, etc.).
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