NET/MASTER Network Control Language (NCL) Programmer's Guide

System Variables Set by the PANEL Verb
Working With Panels
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2. Internal validation handles all error processing automatically and redisplays the
panel, if errors occur.
3. The NCL process determines whether the INWAIT interval has expired by testing
&SYS.INKEY for a null value.
4. If a requested panel does not exist, or some other serious error occurs, the NCL
process terminates with an error message unless you have set an error handler by
using the PANEL_ERROR error handler.
Panel Processing When CONTROL PANELRC Is Set
If you set CONTROL PANELRC, &SYS.RETCODE can contain a value of 0, 4, 8, 12, or
16, as described below.
Return Code 0. This return code indicates that one or more panel input fields have been
modified (this includes overtyping data) and internal validation has not detected any
errors. This return code indicates if any field data have been changed. This lets you
decide if a file record must be updated, or whether it was displayed only so updating
can be bypassed.
The return code setting is determined from the terminal's modified data tag, a flag set
by the terminal when field data is altered. If data has been overtyped but not altered,
this flag is set and a return code of 0 given.
This return code applies only to the last input from the screen. If the NCL process
accepts input from a screen where some data is changed, and then redisplays the
panel, which is then not modified, any earlier indications of data modification are lost.
Your NCL procedure must allow for this situation.
Return Code 4. This return code indicates that no input fields on the panel have been
modified and internal validation has not detected any errors. This return code is used
with return code 0 to decide whether further data processing is required.
Take care when using this return code if multiple interactions with the screen can
occur.
This return code applies only to the last input from the screen. If the NCL process
accepts input from a screen where some data is changed, and then redisplays the
panel, which is then not modified, any earlier indications of data modification are lost.
Your NCL procedure must allow for this situation.
Return Code 8. This return code indicates that internal validation has detected an error
in an input field. When CONTROL PANELRC is in effect, automatic error-condition
processing is suppressed, so the NCL process is notified by this return code. The
&SYSMSG variable contains the text of the error message: for example, NOT WITHIN
RANGE. The &SYS.PANEL.FLD system variable contains the name of the input field
in error; this is the name of the variable, less the ampersand (&), that receives data
entered into that field.
When this return code is set, the NCL process can ignore the error and take alternative
action: for example, the NCL process can display a help panel, alter the error text
message by assigning a new message in the &SYSMSG variable, or redisplay the panel