DIM I AS LONGLONG
 
 MACRO TenMillion = 10 * 1000 * 1000
 
 OPEN "Test" FOR BINARY NEW AS FP1
 
 DIM A$ * TenMillion + 1           ' a VERY LARGE STRING 
 
 ! memset(A,65,TenMillion);         // memset is a lowercase  "C" stdlib func
 
                                    ' In this example, we set every byte in A$ 
 PUT$  FP1, A$, LEN(A$)            ' to ASCII 65 ( the letter "A" ) 
 CLOSE FP1                          ' then write A$ out to a file in one swoop 
 ' The whole process takes about 2 seconds 
 ' on my 300mhz Pentium 
 
 I = LOF("TEST")                   ' So, how big is the file? 
 PRINT "LENGTH OF TEST FILE IS", I  ' If it's TenMillion it worked 
 KILL "TEST"                       ' Don't need the file anymore

Result:

 LENGTH OF TEST FILE IS 10000000