Re: ancient OS history, ARM is sort of channeling the IBM 360

On Wed, 26 Jun 2024 16:12:58 -0000 (UTC), John Levine wrote:

According to Lawrence D'Oliveiro  <ldo@nz.invalid>:
>

possible to request “locate mode”, where it returns the address of a
record directly within its internal buffers. But there are many
restrictions on this, among other things:
>
* It only works for reads, not for writes

 
It works fine for writes on IBM systems. PL/I even has a LOCATE
statement to get a buffer to write into.

I found this manual
<http://bitsavers.trailing-edge.com/pdf/ibm/360/tss/GC28-2045-1_Time_Sharing_System_PLI_Language_Reference_Manual.pdf>.
On page 96, it says

    The LOCATE Statement
    --------------------

    The LOCATE statement can be used only with a BUFFERED OUTPUT
    SEQUENTIAL or TRANSIENT file. (Note: A program that uses a
    TRANSIENT file cannot be executed on TSS/360.) It allocates
    storage within an output buffer for a based variable, setting a
    pointer to the location in the buffer as it does so. This pointer
    can then be used to refer to the allocation so that data can be
    moved into the buffer. The record is written out automatically,
    during executiong of a subsequent WRITE or LOCATE statement for
    the file, or when the file is closed.

So it has its own limitations on applicability. For example, it only
seems to work for writes, not reads.