How can a file contain null bytes?

Question

How is it possible that files can contain null bytes in operating systems written in a language with null-terminating strings (namely, C)?

For example, if I run this she

Answer 1

Because a file is just a stream of bytes, of any byte including null byte. Some files are called text files when they only contain a subset of all the possible bytes: the printable ones (roughly alphanumeric, spaces, punctuation).

C strings are sequence of bytes terminated by a null byte, just a matter of convention. They are too often the source of confusion; just a sequence terminated by null, means any non-null byte terminated by null is a correct C string! Even one that contains a non printable byte, or a control char. Be careful because your example is not a C one! In C printf("dummy\000foo"); will never print foo as printf will consider the C string starting at d and ending at the null byte in the middle. Some compilers complains about such a C string literal.

Now there is no direct link in between C strings (that generally also contains only printable char) and text file. While printing a C string into a file generally consists in storing only its subsequence of non null bytes.