TIMER - QB64 Wiki

TIMER

From QB64 Wiki

Jump to: navigation, search

The TIMER function returns the number of seconds past the previous midnite down to an accuracy of 1/18th of a second.


QB

Contents

Syntax

seconds! = TIMER

QB64

Syntax

seconds# = TIMER[(accuracy!)]


  • TIMER return values range from 0 at midnight to 86399! A comparison value must stay within that range!
  • INTEGER or LONG second values range from 0 at midnight to 86399 seconds each day.
  • Qbasic can return SINGLE values down to about .04 or 1/18th (one tick) of a second accurately.
  • QB64 can read DOUBLE accuracy down to 1 millisecond. Example: start# = TIMER(.001)
  • Use DOUBLE variables for millisecond accuracy as SINGLE values are only accurate to 100ths of a second later in the day!
  • TIMER loops should use a midnight adjustment to avoid non-ending loops in Qbasic.
  • TIMER can also be used for timing program Events. See ON TIMER(n) or the TIMER (statement)
  • QB64 can use a _DELAY down to .001(one millisecond) or _LIMIT loops per second. Both help limit program CPU usage.


Example 1: Delay SUB with a midnight correction for when TIMER returns to 0. QB64 can use _DELAY for delays down to .001.

DO PRINT "Hello"; Delay .5 'accuracy down to .05 seconds or 1/18th of a second in Qbasic PRINT "World!"; LOOP UNTIL INKEY$ = CHR$(27) 'escape key exit END SUB Delay (dlay!) start! = TIMER DO WHILE start! + dlay! >= TIMER IF start! > TIMER THEN start! = start! - 86400 LOOP END SUB

Explanation: When the delay time is added to the present TIMER value, it could be over the maximum number of 86399 seconds. So when TIMER becomes less than start it has reached midnight. The delay value then must be corrected by subtracting 86400.


Example 2: Looping one TIMER tick of 1/18th of a second (ticks per second can be changed)

DEF SEG = 0 ' set to PEEK and POKE TIMER Ticks DO ' main program loop ' program code POKE 1132, 0 ' zero Timer ticks DO ' delay loop x% = PEEK(1132) IF x% <> px% THEN PRINT x%; px% = x% LOOP UNTIL x% >= 18 '18 ticks in one second PRINT "code " ' program code LOOP UNTIL INKEY$ = CHR$(27) DEF SEG ' reset segment to default END

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 code 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 code 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 code

Explanation: The POKE before the delay loop sets the tick count to 0. The PEEK count increases until the tick count returns 18 ticks and ends the loop. The same thing could be approximated by using a delay loop with: second! = TIMER + 1


Example 3: Using a DOUBLE variable for TIMER(.001) millisecond accuracy in QB64 throughout the day.

ts! = TIMER(.001) 'single variable td# = TIMER(.001) 'double variable PRINT "Single ="; ts! PRINT "Double ="; td#

Single = 77073.09 Double = 77073.094

Explanation: SINGLE variables will cut off the millisecond accuracy returned so DOUBLE variables should be used. TIMER values will also exceed INTEGER limits. When displaying TIMER values, use LONG for seconds and DOUBLE for milliseconds.


See also:



Navigation:
Go to Keyword Reference - Alphabetical
Go to Keyword Reference - By usage
Go to Main WIKI Page
Personal tools