Important remark on logical record headers

The logical record header consists of 3 words minimum, but the standard form has four words, being:

1. the logical record length
2. the logical record type identifier
3. the logical record header length
4. the logical record sequence number.

Of these, words 1 and 3 will always be provided by the output routines when writing (basic protection).

Words 2 and 4 of the logical record will always be assigned the values described above when the user writes via calls to EPOUTS.

For use with EPOUTL, two status words, number 5 and 6, are used to assign values in the following way:

let the status words be S5, S6, S12 and the header words be H2, H4,

then

if S5 $\ge 0$

H2 is set to S5 by EPOUTL

if S5 < 0

H2 is not set by EPOUTL, i.e. the user should have set it before calling EPOUTL.

if S6 $\ge 0$

H4 is set to S12 (!) by EPOUTL

if S6 < 0

H4 is not set by EPOUTL, i.e. the user should have set it before calling EPOUTL.