Sean Astin is the greatest BASIC programmer of our generation

I saw this headline and pictured him as a hobbit terminator, with BASIC code scrolling down one side of his field of view.

Does BASIC allow padded string formatting? If so, you only need the one loop.

No, but there are other tricks, such as prepending enough zeros and then taking the rightmost 4 characters from the string...

FOR I = 0 TO 9999 : A$ = RIGHT$("000"+STR$(I),4) : ... rest of the code : NEXT I

DIM FourDigitPassword INTEGER ?