14 LOCATE 23,15:PRINT "Press the ";:COLOR C2,C1:PRINT "space bar";:COLOR C1,C2:PRINT" to begin illustration of variables."
15 IF INKEY$<>"" THEN 15
16 IF INKEY$<>" " THEN 16 ELSE FOR I=1 TO 23:LOCATE I,1:PRINT SPACE$(80);:NEXT
17 LOCATE 1,9:PRINT "In the algebraic equation"
18 LOCATE 3,35:COLOR C3,C4:PRINT "Y = X + 19";:COLOR C1,C2:PRINT ","
19 LOCATE 5,9:COLOR C3,C4:PRINT "Y";:COLOR C1,C2:PRINT " and ";:COLOR C3,C4:PRINT "X";:COLOR C1,C2:PRINT " are variables (because their values can vary), but ";:COLOR C3,C4:PRINT "19";:COLOR C1,C2:PRINT " is a";"constant (its value never changes)."
20 DATA 66,32,75,12
21 FOR I=1 TO 4
22 READ X
23 LOCATE 8,9:PRINT "If the value of ";:COLOR C3,C4:PRINT "X";:COLOR C1,C2:PRINT " is";:COLOR C3,C4:PRINT X;:COLOR C1,C2:PRINT "...";:ROW=CSRLIN:COL=POS(0)-4:PRINT SPACE$(30):LOCATE 12,35:PRINT "Y = X + 19"
24 GOSUB 31
25 LOCATE 12,38:COLOR C3,C4:PRINT X:GOSUB 31
26 LOCATE ROW,COL:PRINT ", then the value of ";:COLOR C3,C4:PRINT "Y";:COLOR C1,C2:PRINT " must be ";:COLOR C3,C4:PRINT USING "##";19+X;:COLOR C1,C2:PRINT ".":LOCATE 14,35:PRINT "Y = ";:COLOR C3,C4:PRINT 19+X
27 GOSUB 31:LOCATE 14,1:PRINT SPACE$(80);
28 NEXT I
29 LOCATE 20,9:PRINT "That's it ... Press the appropriate ";:COLOR C3,C4:PRINT "function key";:COLOR C1,C2:PRINT " to continue."
30 NEW
31 BEEP:LOCATE 20,26:COLOR C1,C2:PRINT "Press the ";:COLOR C2,C1:PRINT "space bar";:COLOR C1,C2:PRINT" to continue."
32 IF INKEY$<>"" THEN 32
33 IF INKEY$<>" " THEN 33 ELSE LOCATE 20,1:PRINT SPACE$(80);:RETURN
