  An upgraded version of the package [BCVEGPY2.0: Chao-Hsi Chang, Jian-Xiong
Wang and Xing-Gang Wu, Comput. Phys. Commun. {\bf 174} (2006) 241-251] is
presented, which works under LINUX system and is named as BCVEGPY2.1. Using
this version with a GNU C compiler, users may simulate the $B_c$-events in
various experimental environments very conveniently. It has been rearranged for
better modularity and code reusability (less dependency among various modules)
than BCVEGPY2.0 has. Furthermore, in the upgraded version a special and
convenient executable-file {\bf run} as default is available according to one's
wish, i.e., the file is obtained in the way that the GNU command {\bf make}
compiles the codes requested by precise purpose with the help of a master {\bf
makefile} in the main code directory. Finally, this paper may also be
considered as an erratum of the original BCVEGPY2.0, i.e., here the errors
(typo mainly) in BCVEGPY2.0 have been corrected.
