15.3.5.1 Text and Binary Files
Windows supports two different types of files: text files and binary
files. On Unix, there is no such distinction. On Windows, any program
which uses files must know whether each file is text or binary, and open
and use them accordingly.
In a text file on Windows, each line is terminated with a carriage
return character followed by a line feed character. When the file is
read by a C program in text mode, the C library converts each carriage
return/line feed pair into a single line feed character. If the file is
read in binary mode, the program will see both the carriage return and
the line feed.
You may have seen this distinction when transferring files between Unix
and Window systems via FTP. You need to set the FTP
program into binary or text mode as appropriate for the file you want to
transfer.
When transferring a binary file, the FTP program simply
transfers the data unchanged. When transferring a text file, the
FTP program must convert each carriage return/line feed pair
into a single line feed.
When using the C standard library, a binary file is indicated by adding
b after the r, w, or a in the call to
fopen . When reading a text file, the program can not simply
count characters and use that when computing arguments to fseek .
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