HP 3000 Manuals HP 3000 Manuals
Types of Intrinsics: Wait and No-Wait I/O
SNA IMF intrinsics can be divided into two categories: intrinsics used
with standard (wait) MPE I/O, and intrinsics used with no-wait MPE I/O.
With standard MPE I/O, a program that has issued an I/O request must
suspend activity until the I/O request has finished. With no-wait I/O,
or unblocked I/O, a program that has issued an I/O request may continue
processing and issue additional I/O requests without waiting for previous
I/O requests to finish. No-wait I/O overlaps the processing of multiple
I/O requests, overlaps I/O with CPU processing, and responds to the
completion of the first of several outstanding I/O requests.
Standard MPE Wait I/O
A program using standard MPE wait I/O must suspend activity after issuing
an I/O request until the request has finished. It cannot issue another
I/O request until the previous request has finished. Table 2-1 shows the
intrinsics that can be used with standard (wait) MPE I/O. These
intrinsics can also be used with no-wait MPE I/O.
Table 2-1. SNA IMF Intrinsics, Wait and No-Wait I/O
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| |
| Intrinsic Function |
| |
| ACQUIRE3270 Allows your program to start Pass Thru on your own terminal or on any |
| free terminal or printer that is not under MPE control. |
| |
| ATTRLIST Returns the locations of attribute characters within a specified |
| subsection or within all subsections of a screen. |
| |
| CLOSE3270 Emulates turning off a specified device. |
| |
| ERR3270 Returns the error message associated with a given SNA IMF intrinsic |
| error number. |
| |
| EXTFIELDATTR (for Asian users) Returns information about the attributes of a |
| specified field, including the DBCS attribute. |
| |
| FIELDATTR Returns information about the attributes of a specified field. |
| |
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Table 2-1. SNA IMF Intrinsics, Wait and No-Wait I/O (cont.)
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| |
| Intrinsic Function |
| |
| OPEN3270 Emulates turning on the power of an emulated IBM 3278 display station |
| or 3287 printer. The OPEN3270 intrinsic allocates the internal |
| screen image used by SNA IMF. |
| |
| PRINT3270 Produces a hard copy of the internal screen image. |
| |
| READFIELD Reads a field of data from the internal screen image and returns the |
| data to an HP application program. |
| |
| READSCREEN Reads all or a specified part of the internal screen image and |
| returns the data to an HP application program. |
| |
| READSTREAM Reads all or part of the untranslated host data stream. |
| |
| RECV3270 Allows your program to receive the screen after modification by the |
| host. Also informs your program that the host has just sent data. |
| |
| RESET3270 Emulates pressing the RESET key on an IBM 3278 display station |
| keyboard. |
| |
| SCREENATTR Returns information about the attributes of the internal screen |
| image. |
| |
| STREAM3270 Emulates typing a series of keystrokes on an IBM 3278 display station |
| keyboard. Allows you to do special function key operations and to |
| update multiple data fields with one intrinsic call. |
| |
| TRAN3270 Emulates pressing one of the transmit keys on the 3278 display |
| station keyboard. TRAN3270 sends modified data to the host the next |
| time the host polls the device. |
| |
| VERS3270 Returns the number of the version of SNA IMF that is being executed |
| on the HP 3000. |
| |
| WRITEFIELD Writes data from the HP application program into an unprotected field |
| of the internal screen image. |
| |
| WRITESTREAM Creates the data stream that an HP application program sends to the |
| host. |
| |
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No-Wait MPE I/O
No-wait MPE I/O requires MPE privileged mode(PM) capability. However,
you do not need PM capability to write an SNA IMF application that uses
no-wait I/O, because the SNA IMF intrinsics themselves have PM
capability. When your application calls the SNA IMF OPEN3270 intrinsic
with bit 15 of the flags parameter set to 1 (the no-wait I/O option),
your program can call any of the SNA IMF intrinsics with no-wait I/O,
whether or not you have PM capability.
If you do not have PM capability, SNA IMF intrinsics are the only
intrinsics you can call with no-wait I/O. If you call, for example, the
MPE FREAD intrinsic, your program will suspend processing until the I/O
request has finished, even though you specified no-wait I/O in your
OPEN3270 intrinsic call.
If your program will use no-wait MPE I/O, it must be written in COBOL II,
FORTRAN, Pascal, C, or SPL. The IOWAIT and IODONTWAIT intrinsics, which
are used with no-wait I/O, return a functional value, pass parameters by
value, allow a variable number of parameters, and set condition codes.
Neither COBOL nor BASIC has these capabilities.
Table 2-2 shows the intrinsics used only with no-wait MPE I/O. Two of
these intrinsics, IOWAIT and IODONTWAIT, are actually MPE intrinsics.You
can call them directly using SNA IMF/V, but if you are using SNA IMF/XL,
you must use the SNA IMF/XL intrinsics IOWAIT3270 and IODONTWAIT3270,
which in turn call the MPE intrinsics IOWAIT and IODONTWAIT.
In addition to the intrinsics listed in table 2-2, all of the intrinsics
listed in table 2-1 can be used with no-wait MPE I/O.
Table 2-2. SNA IMF Intrinsics, No-Wait I/O Only
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| |
| Intrinsic Function |
| |
| ABORT3270 Aborts an outstanding no-wait RECV3270 or TRAN3270 request. |
| |
| IODONTWAIT (SNA IMF/V only) Informs a user program that a previous I/O operation |
| has completed. |
| |
| IODONTWAIT3270 (SNA IMF/XL only) Informs a user program that a previous I/O |
| operation has completed. |
| |
| IOWAIT (SNA IMF/V only) Waits for a previous no-wait I/O request to |
| complete. |
| |
| IOWAIT3270 (SNA IMF/XL only) Waits for a previous no-wait I/O request to |
| complete. |
| |
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WARNING Privileged mode bypasses the normal checks and restrictions that
apply to standard users (those using blocked I/O). It is
possible for a privileged mode program to destroy file
integrity, including the MPE operating system. On request,
Hewlett-Packard will investigate and attempt to resolve problems
resulting from using privileged mode. Although this service is
not available under the standard service contract, it is
available on a time and materials basis. Hewlett-Packard does
not support, under any type of contract, corrections or changes
to the MPE operating system.