Commodore VIC-20 - Page 39

execution continues with the next line number in the program. A
true result makes the program either branch to the line number after
the word THEN or execute whatever other BASIC statements are
found on that line.
EXAMPLE 1:
100 INPUT "TYPE A NUMBER1'; N
110 IF N <= OTHEN 200
120 PRINT "SQUARE ROOT-" SQR(N)
130 GOTO 100
200 PRINT "NUMBER MUST BE >0"
210 GOTO 100
This program prints out the square root of any positive number.
The IF statement here is used to validate the result of the INPUT.
When the result o( N < - 0 is true, the program skips to line 200,
and when the result is false the next line to be executed is 120. Note
that GOTO is not needed with IF ... THEN, as in line 110 where
THEN 200 actually means THEN GOTO 200.
EXAMPLE 2:
100 FOR L = 1 TO 100
110
IF RND(1} < .5 THEN X - X + 1 : GOTO 130
120 Y = Y + 1
130 NEXT L
140 PRINT "HEADS- " X
150 PRINT "TAILS = " Y
The IF in line 120 tests a random number to see if it is less than .5.
When the result is true, the whole series of statements following the
word THEN is executed: first X is incremented by 1, then the
program skips to line 130. When the result is false, the program
drops to the next statement, line 120.
EXAMPLE 3:
100 PRINT CHRS(147);
110 FOR X = 1 TO 23
120 FOR Y - 1 TO 22
130 IFX = 23ANDY = 22THENPRINTCHR$(157)CHR$(148);
140 PRINT "Z";
150 NEXT:NEXT
160 GOTO 160
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