Re: Why I've Dropped In

On Sat, 14 Jun 2025 16:45:23 +0000, Stephen Fuld wrote:

On 6/14/2025 3:48 AM, Thomas Koenig wrote:

Which made nonsense the concept of making data relocatable by
always using base registers.

>
Forgive me, but I don't see why.  When the program is linked, the COMMON
block is at some fixed displacement from the start of the program.  So
the program can "compute" the real address of the data in common blocks
from the address in its base register.

The purpose of a COMMON block is to share variables between the main
program and subroutines.
On the System/360, a FORTRAN compiler typically compiled each subroutine
in a program separately from every other subroutine. They just got
linked together by the linking loader in order to run.
So no subroutine would know where a COMMON block created by loader for
the main program would be unless that information was given to it - and
the loader would give it that information, in the form of a full 24-bit
address constant, so it didn't have to be passed as a parameter.
John Savard