FZRUN - write a RUN record

To write a start-of-run or end-of-run record:

CALL FZRUN (LUN,NRUN,NUH,IUHEAD)

with    LUN:  logical unit number

       NRUN:  run number,
               if  +ve: new run, run number literal
                  zero: new run, increase current run number by one
                   -ve: end-of-run record

        NUH:  length of the user information, may be zero, < 401

     IUHEAD:  NUH words of user information, integers only

Write / Error status returned: as for FZOUT

A start-of-run record will be preceded by an end-of-run signal if the last action on the file was the writing of a data-structure.

The request to write an end-of-run will be by-passed if the last action on the file was the writing of EoR or EoF.

For the media 'memory' or 'channel' the writing of end-of-run, if needed, should be requested by an explicit call to FZRUN with NRUN negative, since an implicit generation will not get through to the user.