Re: STREAM I/O questions

Ron Shepard <ron-shepard@xxxxxxxxxxxxxxxxxx> wrote:
< jfh wrote:

<> A problem with unit numbers that hit me 30 or so years ago was that a
<> certain commercial graphics package of Fortran subroutines used an
<> assortment of undocumented unit numbers for its own purposes,

< I think a lot of software did this 30 years ago back before
< open/close/inquire statements were available using preconnected
< units and/or some kind of JCL incantation.

The DEC compilers would create a file named after the unit,
like FOR001.DAT

For IBM, you needed a JCL DD statement for each unit.
If closed source software used a unit, it would have to
be documented such that the appropriate DD statement would
be supplied. The system cataloged procedures normally
supplied DD statements for 5, (SYSIN), 6 (SYSOUT=A, line printer),
and 7 (SYSOUT=B, card punch). The number of available units
is a sysgen option, likely more on larger machines.

< Open statements were
< available on, for example, some of the DEC compilers and operating
< systems before f77, but not on very many machines made by many other
< vendors. F77 fixed this, of course, but that would not really be
< popular until the mid 80's, and even then often along with the older
< version of the compiler that supported only the preconnected units.


-- glen