ON TIMER(n)
Revision as of 22:11, 7 November 2010 by imported>Clippy
The ON TIMER statement sets up a timed event to be repeated at specified intervals.
Description
- In Qbasic the INTEGER seconds parameter can be from 1 to 86400 seconds(one day).
- A TIMER ON statement must be made before an ON TIMER event is enabled in QB or QB64.
- TIMER STOP remembers previous events when enabled by a TIMER ON statement and the ON TIMER statement(s) may be executed immediately if a timer event has occurred.
- TIMER OFF disables timer event trapping. Events will not be remembered in a subsequent ON TIMER statement.
- ON TIMER events will interrupt a SLEEP call and return to normal program procedures.
- Qbasic can only use one TIMER event at a time and code must be in the main code.
- Can use multiple timers and SINGLE floating point second values down to one millisecond(.001).
- If the TIMER number is omitted, the TIMER used is the base timer. That TIMER cannot be freed using TIMER[0] FREE. No number referance is used for that timer and keeps QB64 compatible with Qbasic.
- Direct SUB procedure calls are also allowed without using CALL.
- Use the _FREETIMER function to save free timer numbers to variables for TIMER statements.
- TIMER(n) FREE releases a timer event after being turned off.
- QB64 allows TIMER statements to also be inside of SUB and FUNCTION procedures.
- Does not currently interrupt SLEEP calls.
- $CHECKING:OFF can disable QB64 event checking. It should ONLY be used with errorless code that needs every CPU cycle!
Example: How to update the time while printing at the same time in a program.
TIMER ON ' enable timer event trapping LOCATE 4, 2 ' set the starting PRINT position ON TIMER(10) GOSUB Clock ' set procedure execution repeat time DO WHILE INKEY$ = "": PRINT "A"; : SLEEP 6: LOOP TIMER OFF SYSTEM Clock: row = CSRLIN ' Save current print cursor row. col = POS(0) ' Save current print cursor column. LOCATE 2, 37: PRINT TIME$; ' print current time at top of screen. LOCATE row, col ' return to last print cursor position RETURN
- NOTE: SLEEP will be interrupted in Qbasic.
See also
- $CHECKING (QB64 C++ Metacommand)