API Commands Appendix A
A-46 ChartScan User’s Manual
? - Query
TYPE
System
EXECUTION
Immediate
SYNTAX
?
Query the present configuration or mode of the command preceding the ?
DESCRIPTION
Most commands have a corresponding Query (?) command formed by appending a question mark (?) to the
command letter. Query commands place their responses into the output queue until the c ontroller retrieves
them. They respond with the present configuration or mode of a previously executed command. When
appropriate, the response from a Query command is in the form of a command string which, if it were executed,
would put the unit into the configuration it was in when the Query was executed.
For instance, the response of the User Terminator Query (V?X) command is in the following form: Vval where
0 < val < 255. This response is in the form of the Set User Terminator (V) command and, if it is s ent to the
unit, it would set the User Terminator to the same value that it had when the Query was issued. Query
responses are always fixed-length strings in a pre-defined format.
Any number of Query commands can be combined into one string to create a specialized status command that
responds with only the information of interest for a given application.
Query commands are immediate. Their responses are generated as soon as they are interpreted, before any
other commands, including the Execute (X) command.
Note: Even though Query commands generate their responses as soon as they are interpreted, they must s till
be followed by an Execute (X) command for proper termination. For more information on command
execution, refer to the X command reference presented later in this appendix.
EXAMPLE
PRINT#1, “OUTPUT07; V1 X V? X”
‘ Get the response of current User Terminator
PRINT#1, “ENTER07”
‘ Retrieve response
INPUT A$
‘ Screen shows V1
PRINT A$
PRINT#1, “OUTPUT07; V0 X V? X”
‘ Change User Terminator and get response
PRINT#1, “ENTER07”
‘ Retrieve response
INPUT A$
‘ Screen shows V0
PRINT#1, “OUTPUT07; V4 V? X”
‘ Change User Terminator and get response - No
intermediate X command
PRINT#1, “ENTER07”
‘ Retrieve response
INPUT A$
‘ Screen shows V0 User Terminator. Response is still V0
because the immediate command V? was executed
before the deferred command V4
PRINT A$
PRINT#1, “OUTPUT07; V? X”
‘ Get User Terminator response
PRINT#1, “ENTER07”
‘ Retrieve response
INPUT A$
‘ Screen shows new User Terminator V4