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64 lines
2.6 KiB
Markdown
64 lines
2.6 KiB
Markdown
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A [TIMER](TIMER) statement enables, turns off or stops timer event trapping. QBasic only uses the base timer, but **QB64** can run many.
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## Syntax
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QB
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> TIMER {ON|STOP|OFF}
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QB64
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> TIMER(*number%*) {ON|STOP|OFF|FREE}
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## Parameter(s)
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* *number* denotes a specific numbered timer event in **QB64 only**. QB64 can run many timer events at once including the base timer.
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* TIMER ON enables event trapping of an [ON TIMER (n)](ON-TIMER-(n)) statement. While enabled, a check is made after every code statement to see if the specified time has elapsed and the ON TIMER [GOSUB](GOSUB) (or [SUB](SUB) in QB64) procedure is executed.
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* TIMER STOP disables timer event trapping. When an event occurs while stopped, it is remembered. If timer events are turned back on later, any remembered events are immediately executed.
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* TIMER OFF turns timer event trapping completely off and no subsequent events are remembered.
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* TIMER(n) **FREE** clears a specific timer event when it is no longer needed. **The base TIMER or TIMER(0) cannot be freed!**
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## Description
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**QB64 only**
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* Get a TIMER number from [_FREETIMER](_FREETIMER) ONLY except when the base timer(no number or 0) is used. Use specific variables or an array to hold each event number value for later reference.
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* If the TIMER number is omitted or 0, the TIMER used is the base timer.
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* Specific TIMER events can be enabled, suspended, turned off or freed using [TIMER (statement)](TIMER-(statement)) ON, STOP, OFF or FREE.
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* TIMER(n) **FREE** clears a specific timer event when it is no longer needed. **The base TIMER or TIMER(0) cannot be freed!**
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**QB64 Timing Alternatives**
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* The [TIMER](TIMER) function can be used to find timed intervals down to 1 millisecond(.001) accuracy.
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* The [_DELAY](_DELAY) statement can be used to delay program execution for intervals down to milliseconds.
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* [_LIMIT](_LIMIT) can slow down loops to a specified number of frames per second. This can also alleviate a program's CPU usage.
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## Example(s)
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How to update the time while [PRINT](PRINT) at the same time in a program.
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```vb
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TIMER ON ' enable timer event trapping
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LOCATE 4, 2 ' set the starting PRINT position
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ON TIMER(10) GOSUB Clock ' set procedure execution repeat time
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DO WHILE INKEY$ = "": PRINT "A"; : SLEEP 6: LOOP
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TIMER OFF
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SYSTEM
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Clock:
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row = CSRLIN ' Save current print cursor row.
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col = POS(0) ' Save current print cursor column.
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LOCATE 2, 37: PRINT TIME$; ' print current time at top of screen.
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LOCATE row, col ' return to last print cursor position
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RETURN
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```
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> NOTE: SLEEP will be interrupted in QBasic.
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## See Also
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* [ON TIMER(n)](ON-TIMER(n)), [TIMER](TIMER)(function)
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* [_DELAY](_DELAY), [_LIMIT](_LIMIT)
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