| TIOS_entries | Constant (Pseudo-Constant)

compat.h

Number of entries in the TIOS jump table.

This pseudo-constant may also be used to determine the AMS version:

684 | 0x2AC | AMS 1.00 (TI-92 Plus only)
972 | 0x3CC | AMS 1.01 (or 1.00 for TI-89), AMS 1.05
1288 | 0x508 | AMS 2.01
1463 | 0x5B7 | AMS 2.02, AMS 2.03
1506 | 0x5E2 | AMS 2.04
1519 | 0x5EF | AMS 2.05
1543 | 0x607 | AMS 2.06 (internal beta), 2.07, 2.08, 2.09
1544 | 0x608 | AMS 3.00, 3.01

It is, in fact, defined globally, in default.h.
You can precisely determine the AMS version using ReleaseVersion.