IO.QST - check status of last IO.QRY call.

Usage:

value = io.qry(func [, token, token2]);
stat = io.qst();

Where:

stat

reflects the zero and minus indicators returned from the last query.

= 0

The previous query ended with a "false" or "conversion failed" status. (Zero indicator was set).

< 0

The previous query ended with a "conversion returned channel index" status. (Minus indicator was set).

> 0

Neither the zero nor the negative indicator was set by .MTBLR.

Examples:

%b/manif/iotable
  ...
/* Process all device SCT's in the system */
sct = io.qry(_FFSDV);    /* Get 1st SCT in system */
do {
   /* process that device */
     ...
   sct = io.qry(_FNSDV, sct);   /* Get next SCT */
} while (0 != io.qst());    /* Until we get a false */

Description:

IO.QST is used to retrieve the status from an immediately preceeding call to IO.QRY. Except for a possible call to .NULL() to retrieve the high order 36 bits of a 72 bit call to IO.QRY, there must be no intervening function calls.

Most calls to IO.QRY do not need a status check. If the call returns, it was successful. There are a few calls such as "convert device name", or "get next SCT" where the system returns a status in the indicator register. IO.QST is used to obtain an interpreted version of the status in the zero and negative indicators.

See Also:

expl b syslib io.qry

Copyright © 2000, Thinkage Ltd.