Earlier I had learned that Paul Pierce’s web site contains images of a number of system tapes for old IBM mainframes. Paul provides some utilities he wrote for making sense of these old tapes, which were written on 7-track drives, with 6-bit BCD characters and 36-bit words.
Tonight I came across Rob Storey’s web site. He’s written file utility programs BCD2IAS, IASMERGE, and FILEBROW that greatly simplify the process of reading, converting, and correcting the tape and card images from Paul Pierce’s web site.
I played with them for a while, and was able to view some of the Fortran IV compiler sources. More work will be necessary to create “fix records” for errors that BCD2IAS can’t detect by itself — it looks like there are occasional missing characters from blocked fixed-length lines, causing the source code to “drift” cyclicly to the left. But the result will be source code for the IBM 7090 Fortran IV compiler!
The bad news is that this compiler shares little if any source code from the original IBM 704/709 Fortran/Fortran II compiler (in particular, it did not contain the sophisticated code optimization components).
Rob’s web site also features an IBM 7094 emulator. (Paul Pierce’s web site has an IBM 709 emulator.)