[ih] Dotted decimal notation

[Nigel Roberts]

I spent a lot of time writing code in Macro-11 in the early 80s. I
personally found octal FAR easier to deal with intuitively than the hex
used by microprocessor code.

I wonde what was better about it? (Apart from 'it goes up to 16')??

On 12/28/20 10:44 PM, John Day via Internet-history wrote:
> Yea, DEC liked octal.  But it would have been so much better if they had settled on Hex. Would have made creating subnet masks much easier!  ;-)
>
>> On Dec 28, 2020, at 16:54, Jack Haverty via Internet-history <internet-history at elists.isoc.org> wrote:
>>
>> IIRC, this convention was created over time by a coalescence of "rough
>> consensus and running code" as the early user programs (Telnet and FTP)
>> were being rewritten to use TCP instead of NCP, so it would have been
>> during the late 70s.   On the ARPANET, e.g., when a particular Telnet,
>> you would type "O <host>/<imp>", e.g., 1/6 to connect to MIT-DMS, host 1
>> on IMP 6, or "O 70" which was the equivalent.   Something new was needed
>> for specifying 32-bit IP addresses.
>>
>> Dotted quad was one early approach, where the 4 numbers could be either
>> octal, if they had a leading zero, and otherwise decimal. 
>> A leading 0 indicated that the number was octal - also a common
>> convention in programming languages at the time.
>>
>> The "dotted decimal" convention evolved from the "dotted quad", with the
>> difference being that the numbers in the "...decimal" form were of
>> course always decimal, regardless of the presence of a leading zero.  
>>
>> I believe all of these forms were created as various people wrote user
>> programs.  The notation is really a design decision of the user
>> interface, converting typed IP addresses into the appropriate 32-bit
>> fields for the underlying TCP code.
>>
>> Some people liked decimal numbers, others liked octal. 
>>
>> One particularly irritating choice was pure decimal, i.e., a 32-bit
>> number represented in decimal (no dotted quad).   The early SRI TIU
>> (terminal concentrator) required the user to input decimal numbers,
>> which were annoyingly difficult to calculate.    E.g., 10.0.0.5, easily
>> recognized as Host 0 on ARPANET IMP 5, had to be typed in its 32-bit
>> decimal format when specifying what remote computer the user wanted to
>> access.  It was difficult to do such calculations in your head; I
>> remember pulling out a calculator to create the appropriate many-digit
>> decimal number.
>>
>> Eventually the "dotted quad" notation reached rough consensus and many
>> host implementations of user apps (Telnet, FTP) permitted that form of
>> specifying a target host.
>>
>> The "dotted decimal" convention eventually superceded the "dotted quad"
>> notation because the quad form was often confusing. 
>>
>> E.g., "ISIF in dotted decimal is 010.002.000.052, or 10.2.0.52", where
>> leading zeroes are ignored.  But in dotted quad,
>> 010.002.000.052 and 10.2.0.52 would not be equivalent.  010 would be
>> network 8 rather than 10, and 052 would be 42 instead of 52.
>>
>> I don't remember who first produced dotted decimal though.   I think
>> you'd have to look at the applications programs of the time (FTP,
>> Telnet) to see what each used for its UI.
>>
>> /Jack
>>
>>
>> On 12/28/20 12:55 PM, Brian E Carpenter via Internet-history wrote:
>>> Can anyone recall when and by whom the dotted decimal notation for IPv4
>>> addresses was invented? This text first appeared in RFC820 (January 1983):
>>>
>>>   One commonly used notation for internet host addresses divides the
>>>   32-bit address into four 8-bit fields and specifies the value of each
>>>   field as a decimal number with the fields separated by periods.  This
>>>   is called the "dotted decimal" notation.  For example, the internet
>>>   address of ISIF in dotted decimal is 010.002.000.052, or 10.2.0.52.
>>>
>>> The leading zeroes are not considered valid these days.
>>>
>>> Thanks 
>>>   Brian Carpenter
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-- 
Nigel Roberts
nigel at channelisles.net
+44 7973 263842 (mobile)