
About
The EXBASIC Reference Manual: syntax, statements, functions, error codes, file handling and assembler interfacing for a Z80 BASIC interpreter.
By its own text this is Microsoft BASIC-80 for CP/M, release 5.03. It prompts "Ok"; Appendix A lists the "New Features in EXBASIC, Release 5.03" against release 4.51 and earlier; and Appendix D gives the CP/M version as MBASIC.COM, signing on "BASIC-80 Version 5.03 (CP/M Version) Copyright 1978 (C) by Microsoft".
Despite the words "Extended BASIC", it has nothing to do with XBAS.COM, the Xtal BASIC that came with the Einstein. For that, see the Tatung Einstein BASIC Manual (Xtal BASIC 4), and our guide BASIC on the Einstein: Which Version Is Which.