Alexandru Dan Corlan MD PhD

RASSIRIS: Emulator for ASSIRIS job assembly and execution on simulated FELIX-C-256 computers


Latest release (0.3.0) (Jan 21, 2024):
Extended documentation release for version 0.3.0: (earlier versions).

Documents from this page are also stored at:

A github repository was started in november 2023 at:, however I will not update it further.

A sourceforge repository:

History of the Felix-C-256

The Felix-C-256 computer was a mainframe computer produced in Romania in the 1970s ( It was more or less a copy of the IRIS-50/IRIS-80 computers produced in France by CII. It was produced by the 'Fabrica de Calculatoare' near Bucharest. Both the computer and the production technology were licenced from CII. It ran the SIRIS-2 operating system that ran also on the IRIS, possibly also the SIRIS-3. A locally developed/modified OS named HELIOS was also probably used.

At their turn the IRISes were produced under licence from SDS (Scientific Data Systems, later XDS after acquisition by Xerox) being similar to the SDS Sigma-7 and Sigma-9 computers. There is a SIMH simulator of the Sigma computers, with an operating system (CP-V) in binary form that works like the original.

However, the IRISes and thus the Felixes, are not binary compatible. The single instruction format has the same field, but not in the same order. In the Sigmas the order is: I,F,B,Q,D. In the IRISes and Felix it is I,B,Q,F,X,D.

The opcodes F are also different. Generally the opcodes perform the same functions, but the usual mnemonics are different as are the codes that correspond to the same actual instruction.

Otherwise, some of the addressing modes, the organisation of the memory and memory management seem to be the same.

The Felix was the only computer available in Romania in the seventies and early eighties. Romania was a socialist country from the Warsaw treaty and there were no private enterprises. The Felixes were to be found in state enterprises and institutions, including 'county computation centers' and could not be purchased privately. Their unreability was legendary. However, they allowed the introduction of computer programming and education curricula relying on a specific, practical, computer system that was even available to some.

A whole generation of computer engineers and programmers was introduced into the field on the Felix Fortran, Cobol and Assiris, as well as Siris control language, starting from high school. Most of those who wrote programs on paper and discussed their functioning never had the opportunity to see a Felix in real life, much less to punch their jobs on cards and actually submit them for execution. For some, this created a lingering frustration.

These were the `golden times' of the real programmers quite a few of which, at least in Romania, were actually women.

While felices remained in operation, or at least on inventories, until the end of the eighties, their place was overtaken in the romanian enterprises by PDP clones, mostly with RSX and RT-11, then by 8080 and Z80 clones running CP/M or ZX spectrum operating systems or the probably locally developed SFDX, which was inspired by RSX, but running on the Z80. Later, 8086 PC-compatible clones overtook the landscape. A hobbist community also developed around home-made ZX Spectrum clones, CP/M and also CP/M-68k. Few unix installations were experimented here and there, until Linux appeared in 1992 (Romania joined back the free world in december 1989).

`Fabrica de Calculatoare' was caught by the 1989 revolution while trying to clone a VAX. It survived for another couple of years, than dissapeared. The whole 'Pipera platform' (industrial campus) where it was situated, together with other computing machinery factories and institutes was transformed and is today a technological campus for (mostly international) software companies.

Of the Felixes, almost nothing remained--except the people who had been initiated in computing and their students and a few programming books and manuals in anticariats.

We could not, initially, find any piece of software, in source or binary other than a few examples in the above mentioned books. There are Corals and Independents still in operation in some informal museums, but no Felices. Almost nothing was to be found about the IRISes online either.

Eventually, we found a few tape images online, mostly with CORAL/INDEPENDENT software, but at least one with some FELIX software--possibly the assiris source code of the SESAM remote access software. Extracting and evaluating these is in progress.

What it is

Based on some of the available books, we try to implement a simulator, not of the Felix (in the SIMH style), but of one single threaded Felix job that must consist of a restriction to the most commonly used instructions and of the ASSIRIS assembler, together with essential control instructions and macros. The job is described by an Ascii file (Felix used EBCDIC) on the standard input, resulting in a printout on the standard output. The input code is assembled in machine code that is probably the same with the Felix one, and executed through interpretation.


The simulator is currently only for Linux. It is written in Ada and published under GPLv2. (Incidently, one of the designers of the SIRIS-3 operating system, Ichbiah, later went on to become the chief designer of the Ada-83 language.) It is a simple program, using only the standard libraries, it should be easy to port on other systems.

You must install the GNU NYU Ada Translator (gnat), the Ada component of the gcc compiler. On debian derived Linuxes use:

apt install gnat

Then, you unpack the distribution zip or tar.gz in a directory and give the command `make'.

To test a job say:



./felix -h
or felix anything to get an 'about' and then a 'help'.

For more, you should really 'use the force' (read the source).


Release 0.3.0

Release 0.2.0

Release 0.1.1 and 0.1.0

Copyright (c) 2002-2023 Alexandru Dan Corlan, ultima modificare 2024/02/08