initially, inserts bytes from the file into the buffer;
decodes bytes to characters as appropriate;
processes formats as defined by entries in format-alist; and
calls functions in after-insert-file-functions.
The function write-region:
initially, calls functions in write-region-annotate-functions;
processes formats as defined by entries in format-alist;
encodes characters to bytes as appropriate; and
modifies the file with the bytes.
This shows the symmetry of the lowest-level operations; reading and
writing handle things in opposite order. The rest of this section
describes the two facilities surrounding the three variables named
above, as well as some related functions. Coding Systems, for
details on character encoding and decoding.