An Upgraded Version of the Generator BCVEGPY2.0 for Hadronic Production   of $B_c$ Meson and Its Excited States
  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. 
Chao-Hsi Chang, Jian-Xiong Wang and Xing-Gang Wu