Game 3 Unit 5 of 6 1 hr learning time

Jiffies and Seconds

Sixty-one jiffies is precise but means little to a human. Divide by 60 and you have seconds — the unit we think in. One line of arithmetic turns the clock's count into a time a person reads at a glance.

83% of Reflex

The clock counts in jiffies because that's how the C64 thinks — sixtieths of a second, ticking along. But a player doesn't think in jiffies. "You took 55 jiffies" lands flat; "you took nine-tenths of a second" lands. The two are the same number wearing different clothes, and the change of clothes is one division.

10 PRINT CHR$(147)
20 POKE 53281,0
30 PRINT "WATCH THE SCREEN..."
40 W=INT(RND(1)*120)+60
50 FOR T=1 TO W*8:NEXT T
60 POKE 53281,1
70 TI$="000000"
80 GET A$:IF A$="" THEN 80
90 RT=TI
100 POKE 53281,0
110 PRINT
120 PRINT "YOUR TIME"
130 PRINT RT;"JIFFIES"
140 PRINT RT/60;"SECONDS"
A C64 screen showing YOUR TIME, then 55 JIFFIES, then .916666667 SECONDS.
The same moment in two units: 55 jiffies, and the same span as a fraction of a second. The machine's clock and the human's clock, side by side.

Line 140 is the new arithmetic: PRINT RT/60;"SECONDS". Because there are sixty jiffies in a second, dividing the jiffy count by 60 gives the time in seconds. The C64 does the sum and prints the result — .916666667, a hair under a second. The long trail of digits is the machine being honest: 55 divided by 60 is exactly that endless fraction, and BASIC shows you all the precision it has.

This is the first time you've done maths on a measurement — taken a raw number the machine gave you and turned it into something a person understands. Printing both, jiffies and seconds, keeps the machine's view and the human's view on screen together. The clock didn't change; only the way you read it did.

Try this

  • Round it off. All those digits are noise. Try PRINT INT(RT/60*10)/10;"SECONDS" to keep just one decimal place — .9 reads far cleaner than .916666667.
  • In your own time. Time how long you can hold your breath, or how long a tune takes, by resetting TI$ and reading RT later. The clock measures any span, not just a flash.

What's next

You can measure a time and show it in seconds — but the program never judges it. In Unit 6 the machine reads the time and gives a verdict — LIGHTNING, QUICK, OK or SLOW — and catches anyone who tries to cheat.