mfc42u是visual c++对unicode的支持，vc默认情况下并不安装，对于安装盗版的vc的朋友如果要用unicode的话，只要复制该文件就可以了，不用有visual c++的原光盘。-mfc42u is a visual c++ for unicode support, vc is not installed by default, for the installation of pirated vc' s friends, if use unicode, then copy the file as long as you can, and do not have visual c++ for the original CD-ROM.