Oh, my, given that it does allow opening files, you could indeed do some "real" tasks with this.  And do some real damage!

I don't want to think about looping through files, but it could reasonably be used to process a file!

cbbrowne@cbbrowne2 ~/G/c/test> cat fileio.bas                                                                                                                                      130 master?
10 OPEN 1,1,1,"TEST.DAT"
20 PRINT#1, 1234
30 PRINT#1, "Hello"
40 CLOSE 1

50 OPEN 2,1,0,"TEST.DAT"
60 INPUT#2, A
70 INPUT#2, I$
80 CLOSE 2

90 PRINT A
100 PRINT I$

The prime number sieve (which does not capture primes into an array, hence never speeds up searches by avoiding dividing by non-primes) is surprisingly fast, all given, finding the first 11302 primes in about 11 seconds.

I'm with Hugh on being disappointed not to have the Waterloo "structured BASIC" extensions.

That said, I hated Structured BASIC at the time; it prevented me from handing in assignments on tiny slips of paper, which inevitably led to the teacher losing my assignment because the piece of paper fell out when he was shuffling papers.  Oh, the good times of doing matrix calculations in Grade 12 "Computer Science"...