Uuencode converts binary files into ASCII and Uudecode converts ASCII characters into binary files. The encoding is necessary to be able to email binary files to systems that would otherwise corrupt these files—such as some UNIX mail systems. A common routine for sending a binary file over the Internet is to compress the binary file using PKZIP and to then use Uuencode to convert the file into ASCII characters. The ASCII file is then emailed to another online user, who uses Uudecode to convert the ASCII character file back into a binary ZIP file.