[vcf-midatlantic] A 4004 Based Microcomputer the Comstar System 4

[Herbert Johnson]

My description of the Comstar 4 product line was in error. Careful 
reading of the ACM/NCC 1975 description by the company, says the 
"compiler" was a device with keyboard and 32-character display, which 
accepted "key per function" features of the PLC language, displayed the 
entered statement, and accumulated the 4004 "compiled" instructions into 
a 256-byte EPROM (likely an Intel 2708). Those ROMS operated the Comstar 
4 controller which operated the application equipment as programmed. 
Other Comstar 4 devices, provided diagnostic and testing of the 
controller and its PLC program.

While the PLC language was claimed to be "FORTRAN-like", the document 
deliberately explains that the compiler product (a machine, not a 
FORTRAN or other program) is used on-site and avoids the need for some 
remote computer to process (assemble or compile) some textual program.

I can imagine the difficulties Christian had, in trying to determine the 
function and operation of the Comstar 4 "computer" and "programmer". 
Especially years ago when knowledge of the 4004/40 was even more obscure.

My error goes to my point, that these very early 4-bt microprocessor 
based products are difficult to interpret from a later view of computing 
and microprocessor development and use.

Regards Herb Johnson


On 1/11/2024 2:57 PM, Herbert Johnson wrote:
> 
> Apparently that Comstar 4, and certainly early use of the Intel 4004, 
> are examples of industrialm controls. From Christian's documents, the 
> Compstar System 4 was a replacement for ladder-logic or PLC (programmed 
> logic) controllers for industrial control. The PLC program was 
> cross-compiled on some mainframe or minicomputer running a FORTRAN 
> program. That was a very common means of microprocessor programming in 
> the early-mid 1970's. Gary Kildall ...  
> produced FORTRAN assemblers and PL/M compilers for Intel's 8008 and 
> 8080, for development of industrial applications. 

-- 
Herbert R. Johnson, New Jersey USA
https://www.retrotechnology.com OR .net
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