Fortran II Hypersource

texdraft.github.io

79 points·texdraft··8 comments

FORTRAN II was a version of Fortran in use from 1958 to 1961, then superseded by FORTRAN IV. (IBM never published FORTRAN III, it was only an IBM internal project.)

https://en.wikipedia.org/wiki/Fortran#FORTRAN_II

you buried the lede in the lead, where it links:

See also LISP 1.5

https://texdraft.github.io/lisp-1.5/listing.html

finally! being able to take the actual CAR and CDR!

CAR here and CDR just below: https://texdraft.github.io/lisp-1.5/listing.html#line-7626

thanks for finding that, i love it!

For those not familiar with these old IBM machines that used decrementing of the index registers, this will help explain all the ??D instructions are there.

https://bitsavers.org/pdf/ibm/704/24-6661-2_704_Manual_1955....

Another lens for the FORTRAN case specifically, in the modern way we tend to say Fortran arrays are 'one' indexed, looking at this old code it is sometimes useful of thinking of it as a limit index, pulling from n-1 -> n. Or at least I found that useful for myself when digging into some of this a long time ago.

Its amazing to me how few instructions it took to write this. I would love to see higher level documentation of how it all fits together.

You might like https://archive.computerhistory.org/resources/text/Fortran/1... and https://archive.computerhistory.org/resources/text/Fortran/1..., although they assume a good deal of familiarity with the machines the compiler ran on.

Thank you!

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