Specifies that a backslash in a path is treated as a directory separator (with the exception that it can be used to escape spaces). For example:

C:\test\ file.c

The first backslash is treated as a separator followed by a t, not an escape sequence representing the tab character. The second backslash escapes the space.

This is the default.

Specifies that a backslash is to be treated as part of an escape sequence to indicate that the character following is a special character. For example:

C:\\test\\file.c

The backslash in this example is a directory separator and must be identified as a special character.