10 REM QBASIC PROGRAM #1
15 REM This program determines if a give number is prime or not prime
20 CLS
30 PRINT
40 INPUT "Please enter a number"; a
50 IF a = 3 THEN GOTO 130
60 LET b = 2
70 PRINT
80 IF (a / b = INT(a / b)) THEN
81  PRINT a; "Is not prime becuase it is divisible by 2"
82  GOTO 160
90 END IF
100 FOR b = 3 TO (a - 1)
110 IF (a / b = INT(a / b)) THEN GOTO 150
120 NEXT b
130 PRINT a; "is a prime number"
140 GOTO 160
150 PRINT a; "is not prime becuase it is divisble by"; b
160 INPUT "Would you like to test another (1=yes/2=no)"; c
170 IF c = 1 THEN GOTO 20
180 IF c = 2 THEN GOTO 210
190 IF c <> 1 OR c <> 2 THEN
191  CLS
192  PRINT "Invalid entry"
193  GOTO 160
200 END IF
210 END