The list form of the OPEN macro constructs a data management parameter
list. You can specify any number of parameters (DCB addresses and
associated options).
There are two forms of the list, the short form and the long form.
The short form list consists of a one-word entry for each DCB or ACB
in the parameter list. The high-order byte is used for the options
and the 3 low-order bytes are used for the DCB address. The long form
list consists of an eight byte entry for each DCB or ACB in the parameter
list. The high order byte is used for the options and the low order
four bytes are used for the DCB or ACB address. For either form of
list, the end of the list is indicated by a 1 in the high-order bit
of the last entry's option byte. The length of a list generated by
a list form instruction must be equal to the maximum length list required
by any execute form instruction that refers to the same list. A maximum
length list can be constructed by one of two methods:
- Code a list-form instruction with the maximum number of parameters
required by an execute form instruction that refers to the list.
- Code a maximum length list by using commas in a list-form instruction
to acquire a list of the appropriate size. For example, coding OPEN
(,,,,,,,,,),MF=L would provide a list of 5 fullwords (5 DCB addresses
and 5 options).
Entries at the end of the list not referred to by the execute-form
instruction are assumed to have been filled in when the list was constructed
or by a previous execute-form instruction. Before using the execute-form
instruction, you can shorten the list by placing a 1 in the high-order
bit of the last DCB entry to be processed.
A zeroed work area on a fullword boundary is equivalent to OPEN
(,(INPUT,DISP),...),MF=L and can be used in place of a list-form instruction.
Allocate four bytes per entry if you wish the effect of MODE=24. Allocate
eight bytes per entry if you wish the effect of MODE=31. The high-order
bit of the last DCB entry must contain a 1 before this list can be
used with the execute-form instruction.
A parameter list constructed by an OPEN, list-form, macro can be
referred to by either an OPEN or CLOSE execute form instruction. The
description of the standard form of the OPEN macro explains the function
of each parameter.
The list form of the OPEN macro is:
[label] |
OPEN |
([dcb address],[(options )],...) ,MF=L [,TYPE=J] [,MODE=24|31] |
dcb address—A-Type Address
- MF=L
- specifies that the OPEN macro is used to create a data management
parameter list that is referred to by an execute form instruction.
- TYPE=J
- coded the same as the standard form. This has no effect on the
macro expansion.
- MODE=24|31
- coded the same as the standard form. This specification must match
that of the execute form. Errors and unpredictable results occur if
the modes are inconsistent.