The Electrologica X1 and X8 Algol Compilers
Although two of the early Algol 60 compilers have been published in listing form
(within pdf files) on the Internet, they do not appear to be available as text
files which could be used to recreate the original executables or to modify to
create new Algol 60 compilers.
On this page I refer to the original documents and associated documentation,
and go on to offer my attempts to convert these listings into editable source
files.
Because the original sources were prepared on Friden Flexowriter
devices, with the Algol 60 compilers themselves using the Flexowriter character
set and encoding, they cannot be represented exactly in 7- or 8-bit ASCII/ANSI/ISO
encodings. In the past, a limitation like this would handled by using some
form of markup such as HTML or TeX, but with the availability of support for
Unicode encodings being more widespread, I have chosen to create these
reconstituted text files in UTF-8 format, with utilities supplied to
export the text in other formats such as HTML and 8-bit ISO-Latin1 text.
Due to the lack of support on this specific web host, plain text files
in Unicode encodings will not display correctly, but the downloaded Unicode
files should read mostly correct on most modern computers on-screen and in text editors.
HTML-encoded versions of these files, which should look almost identical,
are supplied here for viewing online.
Original documents which embed the source listings:
Associated documentation related to these compilers:
Rebuilt source for the Electrologica X1 Algol 60 compiler, written in Pascal
The embedded listing in the PDF file was good quality as it appeared to have been created
from a textual source file (though that file doesn't appear to have been shared anywhere)
but a simple cut & paste did not preserve the indentation. Therefore I extracted the
text along with its x,y position within the page from the PDF and
wrote a program to recreate the text listing with the correct
indentation. The Pascal source file does not use any Flexowriter characters, so this file
is in normal readable ASCII text.
Rebuilt source for the Electrologica X8 Algol 60 compiler, written in Algol 60
In the case of the Algol 60 source for the X8, I recreated the text from the OCR data in the PDF file. Unfortunately the
quality of the OCR was terrible, with multiple errors on every line, so the text file is as much a re-keying as it is an OCRing.
To simplify the re-keying (and considerably reduce the data-entry time) I did not copy the spacing of the original
exactly (unlike what our team did in recreating the KDF-9 WAlgol!) - indeed in many cases I did not even approximate the indentation, relying on a later re-indentation using
the original SOAP (if we can get it running again) or my own Algol 60 reformatter, which indeed I have used below. If I have time, I may go over this document again and restore some of the indentation by hand.
Note that the Algol 60 source uses underlining for keyword stropping.
- x8algol.a60 as a scanned listing, in pdf format
- x8algol.a60 as a Unicode text file - this should be considered the master copy if you are editing the source.
- x8algol.a60 in HTML format for viewing online, exported from Unicode
- x8algol.alg exported to 7-bit ASCII suitable for compiling with the 'marst' Algol 60 compiler. Uses reserved keywords :-( Other forms of stropping could be exported from the Unicode master.
- x8algol.a60 prettyprinted by my source code formatter to HTML format for viewing online. This
output does not break long lines and uses the Algol 60 character set.
Electrologica X8 simulator in Algol 60 (1971)
From https://github.com/cwi-software-archive/EL-X8/blob/main/content/Simulator/X8Sa.a60
The following information is taken directly from:
The EL-X8 Simulator X8S
The EL-X8 simulator X8S, written in Algol 60 at the Mathematisch Centrum in Amsterdam, allowed testing of EL-X8 assembly programs during normal operation hours.
The program X8S simulates machine instructions of the EL- X8; it was written entirely in Algol 60, without using special code procedures. The full instruction set of the CPU of the EL-X8 has been implemented, including memory protection and control state. The only component of the input/output processor CHARON that was implemented is the IP facility. The actions and reactions of the simulator during a run (tracing, unusual situations, etc.) are controlled by a Master program, written in a simple control language.
The zip file contains three programs:
- The X8 simulator X8S in Algol 60 in two versions: one with underlined reserved words (X8S.a60u), and one with reserved words between single quotes (X8S.a60a).
- The accompanying Master program X8Sm.71.cdl, to be called by the tracing-facility of X8S.
- A machine-code program in ELAN, both for examining the EL-X8 computer and for testing the EL-X8 simulator X8S.
The Master program can be called from many places in the simulator program, and its first task is finding out what is going on. This requires a sequence of tests, similar to those in a parser. This being part of a compiler construction project, the Master program was written in CDL, the `Compiler Description Language' designed by Kees Koster.
The CDL processor supplied the Algol 60 code for the if-then-else-if-then structure, and the Algol 60 code for the actions was defined by macros. The CDL processor produced (compressed) Algol 60. The Algol 60 code produced by the CDL processor from the Master-program X8Sm.71.cdl can be seen in the program X8S, starting from line 449.
The simulator was described (in Dutch) in Beschrijving van de XS-simulator X8S (1972).