CAnn (Command Attention) keyword for display files

You use this file-level or record-level keyword to specify that the function key specified in the keyword (CA01 through CA24) is available for use.

It is to be used as a command attention (CA) key. No input data is transmitted from the device. Response indicators 01 through 99 are valid.

See System/36 environment considerations for display files for special considerations when you specify the CAnn keyword in files that are used in the System/36 environment.

The format of the keyword is: 
CAnn[(response-indicator ['text'])]
If you specify this keyword and the display station user presses the specified function key, the following situation happens:
  • All other function key response indicators in the input buffer are set off (hex F0).
  • The response indicator, if specified with the CAnn keyword, is set on (hex F1).
  • The IBM® i data management feedback area is updated.
  • Data already in the input buffer remains unchanged except that the response indicator (if specified) is set on.
  • Control is returned to your program.

If you specify a response indicator and the key is pressed, the response indicator is set on and returned to your program. (The text information is associated with the indicator and is used by high-level language compilers to help in program documentation.)

If the display station user presses a function key and you have not specified it as either a command function (CF) key or a command attention key, the IBM i operating system displays a message to the display station user indicating that the key is not valid at that time.

You can use combinations of CA and CF keywords within the same display file, but you cannot specify the same key number as both CA and CF keys. For example, CA02 and CF02 are not valid in the same display file.

Note: File level CA and CF keys are extended to the record level. This must be considered when assigning key numbers. For example, if CA02 is specified at file level and CF02 is specified at record level, CF02 is an error.

If you specify a key in the range 1 through 9, you must supply the leading zero in the keyword (for example, CA04).

Option indicators are valid for this keyword.

Validity checking

When the display station user presses a CF key, the data from fields with their MDT set on is placed into the input buffer before validity checking is done. Any errors in the data are then detected, and the appropriate error messages are sent to the display. Because validity checking is not done until after the data is placed in the input buffer, pressing a valid CA key after the CF key can cause incorrect data to be returned to your program. This condition is not a problem as long as your program does not process the input data when the CA key is pressed.

This condition can be prevented in either of two ways:
  • Do not allow the use of CA keys. Specify CF keys, which cause validity checking to be done on the data.
  • Do not specify any of the following validity checking keywords if CA keys are allowed:
    CHECK(M10)
    CHECK(M11)
    CHECK(VN)
    CHECK(VNE)
    COMP (EQ, NE, LT, NL, GT, NG, LE, GE)
    RANGE
    VALUES

Function keys valid for command attention keys at processing time

As a general rule, the last output operation determines which function keys are valid. However, the following list shows exceptions to this rule:

  • When an operation sends no data to the display, the validity of various function keys is not changed. Such operations include:
    • An output operation to a subfile record
    • An update to a subfile record
    • An output operation to a subfile control record that only clears, deletes, or initializes a subfile without displaying the subfile or the subfile control record
  • An output operation that displays an error message by selecting ERRMSG (Error Message) or ERRMSGID (Error Message ID) can also select a CA or CF key to be valid while the error message is displayed.
  • If MNUCNL (Menu Cancel), MNUBARSW (Menu Bar Switch), or SFLDROP (Subfile Drop) is specified for a subfile, the validity of the CA or CF key specified for the SFLDROP keyword is determined by the last output operation. However, as long as the subfile is displayed, the CA or CF key, when valid, acts only as a Drop key.
  • If SFLFOLD (Subfile Fold) is specified for a subfile, the validity of the CA or CF key specified for the SFLFOLD keyword is determined by the last output operation. However, as long as the subfile is displayed, the CA or CF key, when valid, acts only as a Fold key.
  • If two subfiles using SFLDROP or SFLFOLD are displayed at one time, the same function key should be specified on both the SFLDROP and SFLFOLD keywords. If they are different, only the key specified for the most recently displayed subfile is in effect. Pressing the function key affects the subfile containing the cursor. If the cursor is not positioned in a subfile, the function key affects the upper subfile.
  • If two subfiles using SFLENTER (Subfile Enter) are displayed at the same time, the only CA or CF key in effect as an Enter key is the CA or CF key specified for the SFLENTER keyword on the most recently displayed subfile. The cursor position at the time the Enter key is pressed determines which subfile is affected.
Note: The following keywords function like CA keys: CLEAR, HELP, HOME, and PRINT (with response indicator specified).

Example

The following example shows how to specify the CAnn keyword.

|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
00011A                                      CA01(91 'End of Program')
00012A                                      CA02(92)
00013A                                      CA03
     A