Here's that program, somewhat improved:
'TEMP, by Ralph A. Esquivel, plots degrees F vs time in seconds
SCREEN 9: Xmax = 640: Ymax = 350
FG = 1 'blue foreground
BG = 7 'white background
COLOR FG, BG
CLS
'draw x-axis
X = 40
LINE (X, Ymax - 60)-(Xmax - 10, Ymax - 60)
LOCATE 22, 5
MULT1 = 10
FOR I = MULT1 TO 170 STEP MULT1
PRINT I - MULT1;
IF I = 10 THEN LINE (X + 32, 140)-(X + 32, Ymax - 60)
NEXT I
'draw y-axis
LINE (X, 140)-(X, Ymax - 60)
LOCATE 10
FOR I = 10 TO 0 STEP -1
PRINT I * 10
IF I = 7 THEN LINE (X, Ymax - 60 - 102)-(Xmax - 10, Ymax - 60 - 102)
IF I = 3 THEN LINE (X, Ymax - 60 - 46)-(Xmax - 10, Ymax - 60 - 46)
NEXT I
'plot temperature points
MULT2 = 1.45
READ TIME
FOR I = 1 TO TIME
X0 = I * 3 + 40 - 2
READ T
TEMP = Ymax - 60 - T * MULT2
Y0 = TEMP
CIRCLE (X0, Y0), 2
PAINT (X0, Y0), 1
SLEEP 1 'simulate data at rate of 1 per second
NEXT I
LOCATE 10, 10
PRINT "Press any key to terminate program"
SLEEP
END
'Temperature data:
DATA 14, 32, 42, 49, 55, 60, 64, 67, 69, 70, 69, 70, 71, 70, 71, 0