Open Function Encoding

OpenFunction specifies the action to be taken depending on whether or not the file exists. This word has the following format:

bits:

1111 11
    5432 1098 7654 3210
    rrrr rrrr rrrC rrOO

where:

C - Create (action to be taken if file does not exist).
    0 -- Fail.
    1 -- Create file.

r - reserved (must be zero).

O - Open (action to be taken if file exists).
    0 - Fail.
    1 - Open file.
    2 - Truncate file.