TOPS-10 Monitor Calls Manual Volume 2 AA-K039D ... - Trailing-Edge

LOOKUP [OPCODE 076]
22.86 LOOKUP [OPCODE 076]
FUNCTION
Selects a file for input. Use FILOP. to pe~form a LOOKUP for an
extended I/O channel. The LOOKUP call 1S meaningful only for
directory devices (disk, DECtape, labelled magnetic tape), and for TSK
devices (initiated for task-to-task communication). It is a no-op for
other devices, always taking the skip return for these.
CALLING SEQUENCE
The LOOKUP monitor call, like the ENTER call, has two calling
sequences: one using a 4-word argument list and one using an extended
argument list. The argument lists for LOOKUP, ENTER, and RENAME UUOs
are identical. These are described in Section 11.13. The four-word
argument list is detailed in section 11.13.1. The extended argument
list is described in Section 11.13.2.
The calling sequence for the LOOKUP UUO is:
LOOKUP channo,addr
error return
skip return
In the call sequence, the program s'upplies the addr, which is the
address of the argument list. R~fer to Volume--l-,-Section 11.13 for
more information about the argument,list.
SKIP RETURN
For DECtape, the monitor returns a 4-word block at addr in the
following form:
Word
o
1
Contents
The SIXBIT file name.
The extension, creation date, and first block number:
Bits
0-17
18-20
21-25
26-35
Contents
The SIXBIT file extension.
The high-order three bits of the file creation
date.
Reserved.
The first physical (data) block number.
2
Remainder of creation date:
Bits
0-23
24-35
Contents
Reserved.
The low-order 12 bits of the file creation date.
3
Length and address of file:
Bits
0-17
18-35
Contents
Negative of number of words in zero-compressed
file.
Address of word preceding the first word of the
file.
22-233