python-classes.txt

To send binary files through certain systems (such as email) that do not allow all data values, they are often translated into a plain text representation (using, for example, Base64). Encoding the data has the disadvantage of increasing the file size during the transfer (for example, using Base64 will increase the file's size by approximately 30%), as well as requiring translation back into binary after receipt. The increased size may be countered by lower-level link compression, as the resulting text data will have about as much less entropy as it has increased size, so the actual data transferred in this scenario would likely be very close to the size of the original binary data. See Binary-to-text encoding for more on this subject.

Microsoft Windows and its standard libraries for the C and C++ programming languages allow the programmer to specify a parameter indicating if a file is expected to be plain text or binary when opening a file; this affects the standard library calls to read and write from the file in that the system converts between the C/C++ "end of line" character (the ASCII linefeed character) and the end-of-line sequence Windows expects in files (the ASCII carriage return and linefeed characters in sequence). In Unix-like systems, the C and C++ standard libraries on those systems also allow the programmer to specify whether a file is expected to be text or binary, but the libraries can and do ignore that parameter, as the end-of-line sequence in Unix-like systems is just the C/C++ end-of-line character.