Q(uick)BASIC Keyword: ON

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ON Keyword

Different Uses

Worth knowing

Useful and cross-version information about the programming environments of QBasic and QuickBasic.

Description/Parameter(s)
  • The ON keyword performs different actions as part of several statements:

  • Enables error trapping when used with the ON ERROR statement.
  • Enables event trapping when used with the event ON statements (COM ON, KEY ON, PEN ON, PLAY ON, STRIG ON, and TIMER ON).
  • Specifies an event to trap when used with the ON event statements (ON COM, ON KEY, ON PEN, ON PLAY, ON STRING, and ON TIMER).
  • Specifies an expression to evaluate when used with the ON...GOSUB and ON...GOTO statements.

See also:

Description/Parameter(s)

The ON keyword is used in various statements to trap events:

⮜ ON COM(n) ⮞ events on communications port n ⮜ COM(n) ON ⮞
⮜ ON KEY(n) ⮞ a keystroke on key n ⮜ KEY(n) ON ⮞
⮜ ON PEN ⮞ lightpen events ⮜ PEN ON ⮞
⮜ ON PLAY(n) ⮞ less than n notes in music buffer ⮜ PLAY ON ⮞
⮜ ON STRIG(n) ⮞ events on joystick trigger n ⮜ STRIG(n) ON ⮞
⮜ ON TIMER(n) ⮞ timer events ⮜ TIMER ON ⮞
⮜ ON UEVENT ⮞ user-defined events ⮜ UEVENT ON ⮞

Other uses of the ON keyword are:

⮜ ON ERROR ⮞ - to enable error handling and specify the error-handling routine
⮜ ON...GOSUB ⮞ - to branch to one of a list of subroutines
⮜ ON...GOTO ⮞ - to branch to one of a list of line labels
Description/Parameter(s)

The ON event statements are used to trap events. For further information, see ON COM, ON KEY, ON PEN, ON PLAY, ON SIGNAL, ON STRIG, ON TIMER, or ON UEVENT:

Specifies a trap Type of event Enables the trap Available in DOS or OS/2 protected mode
⮜ ON COM(n) ⮞ Events on a communications port ⮜ COM(n) ON ⮞ DOS & OS/2
⮜ ON KEY(n) ⮞ A keystroke ⮜ KEY(n) ON ⮞ DOS & OS/2
⮜ ON PEN ⮞ Lightpen events ⮜ PEN ON ⮞ DOS only
⮜ ON PLAY(n) ⮞ Fewer than queluelimit% notes in the background-music queue ⮜ PLAY ON ⮞ DOS only
⮜ ON SIGNAL ⮞ An OS/2 signal event ⮜ SIGNAL ⮞ OS/2 only
⮜ ON STRIG(n) ⮞ Events on a joystick trigger ⮜ STRIG(n) ON ⮞ DOS only
⮜ ON TIMER(n) ⮞ Timer events ⮜ TIMER ON ⮞ DOS & OS/2
⮜ ON UEVENT ⮞ User-defined events ⮜ UEVENT ON ⮞ DOS & OS/2

See also: