17 August 2016

While Microsoft QBasic does allow programs with line numbers, idiomatically one is meant not to. So this version does not have them. Stack exhaustion was a problem for QBasic with the way the Applesoft version uses FOR/NEXT, so program flow has improved slightly as a side effect of dealing with that. The MODulus function is put to use as well.

       SUB primes (n AS INTEGER)
         count = 2
         found = 0
         index = 0
         DIM prime(n - 1)
         DO WHILE found < n
           PRINT count
           prime(found) = count
           found = found + 1
NOTPRIME:  count = count + 1
           index = 0
           DO
             v = count MOD prime(index)
             index = index + 1
           LOOP UNTIL v = 0 OR index = found
           IF v = 0 THEN GOTO NOTPRIME
         LOOP
       END SUB