[ih] Fwd: As Flag Day approaches at CMU

[Jack Haverty]

ITS at MIT circa early 1970s used a naming convention for files -- 
<device>:<directory>;<name1> <name2>   So, for example, I logged in to 
MIT-DM as JFH.  My files on disk were things like DSK:JFH;THESIS TJ6    
File names were limited to alphanumerics of 6 characters or less 
(motivated by what you could encode into a 36-bit PDP-10 memory location).

Once the ARPANET and NCPs appeared, the 'net was a new toy, so people of 
course experimented with how to use it.  I don't remember the details or 
timing (sometime in early 1970s), but at but at some point the Message 
Of The Day announced a new capability - you could use files on some 
other ITS machine just by using a different <device> to specify the DSK 
on some other ITS machine.

So, for example, from the MIT-AI machine a user could get to my file on 
the DM machine by specifying DM:JFH;THESIS TJ6.

Similarly, from my account on MIT-DM, I could get to another machine's 
files by using a name such as AI:TK;NEWS ITS to get at Tom Knight's file 
on the AI machine.

This provided more flexibility than FTP.  You could use a remote file in 
any program that knew how to use files on devices.  To the program, the 
remote disk looked and behaved like a local disk. (More or less - 
problems of "global LANs" were still be be surfaced)

I don't recall at all how this worked, or who implemented it.  IIRC, it 
took advantage of an interprocess communication capability called the 
"JOB/BOJ device", which enabled one program to open a JOB device, and 
another program to open the corresponding BOJ (JOB reversed) device, and 
send whatever they liked back and forth.  But I don't remember details.

We also had the ability for one process (aka "job") to map some or all 
of another process' address space into its own address space.  I can't 
recall if anyone got motivated to get that working across the ARPANET 
though.   If so, it would probably have been done using the same 
internal mechanisms that got the remote file systems capability.

However, for anyone curious, the ancient ITS system is online and has 
even been resurrected so you can look at the code or even run it on your 
modern computer - see https://github.com/PDP-10/its

Jack Haverty (JFH at MIT-DM in the 70s)

On 9/6/25 09:28, Guy Almes via Internet-history wrote:
> Noel,
>   So this was a real networked file system (and not just lots of FTP)?
>   Very interesting,
>     -- Guy
>
> On 9/6/25 11:35 AM, Noel Chiappa via Internet-history wrote:
>>
>>      > From: Guy Almes
>>
>>      > There are probably a number of ARPAnet sites where the ARPAnet
>>      > served this LAN role in the pre-Ethernet days.
>>
>> Notably MIT, where the 4 ITS machines shared their file systems over the
>> ARPANET.
>>
>>     Noel
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