The oldest program I wrote that has been used routinely since then was a Basic application to do precise calculation of some chemical assays.
This was on a HP benchtop gas analyzer where I had added the HP Basic option which was needed to handle the complexity of petroleum data like only companies having mainframes had been able to, up until 1979. Most other research operations did not need Basic since the underlying expert system was adequate for less data-intensive work. Those who had a bare-bones analyzer were way ahead of most of the world though, which was still going with analog chart recorders and simpler mathematical calibration techniques that had been well-established.
Interestingly, there are still plenty of non-petroleum gases and other analytes where the raw analog data is so simple that no computer has ever been needed at all, some needing not a calculator nor even a slide rule. But people naturally have all-computerized systems in the modern world anyway, including the complex software that for such simple analysis provides more room for error than the analog days. In theory and in practice as directly observed.
But the chemical assays were not related to the gases, I just liked having a personal desktop system that would compute, and wrote a couple hundred lines that would get it done in a way that was completely auditable. The workflow included manually entering data that had been gathered from bench work in the non-gas labs.
Slightly different syntax allowed my app to run on the P-E equivalent to the HP, and I managed to keep at least one P-E running until 2014 so I could operate the vintage analyzers in my own lab. But stopped running my old chem app on them in 1993 when my employer got their first office PC with Windows 3.1 and GW-Basic. So that was the first actual DOS version of the same old thing, which is the one still in use on my FAT32 partition when I boot to DOS, as well as run from the command line when booted to 32-bit Windows.
When it comes to timestamps a couple old EXEs that have been carried forward on the FAT32 volume are Tetris and Battle Chess from 1989 which I can still run any time since.
That looks like it for files that are actually useful still.
This was on a HP benchtop gas analyzer where I had added the HP Basic option which was needed to handle the complexity of petroleum data like only companies having mainframes had been able to, up until 1979. Most other research operations did not need Basic since the underlying expert system was adequate for less data-intensive work. Those who had a bare-bones analyzer were way ahead of most of the world though, which was still going with analog chart recorders and simpler mathematical calibration techniques that had been well-established.
Interestingly, there are still plenty of non-petroleum gases and other analytes where the raw analog data is so simple that no computer has ever been needed at all, some needing not a calculator nor even a slide rule. But people naturally have all-computerized systems in the modern world anyway, including the complex software that for such simple analysis provides more room for error than the analog days. In theory and in practice as directly observed.
But the chemical assays were not related to the gases, I just liked having a personal desktop system that would compute, and wrote a couple hundred lines that would get it done in a way that was completely auditable. The workflow included manually entering data that had been gathered from bench work in the non-gas labs.
Slightly different syntax allowed my app to run on the P-E equivalent to the HP, and I managed to keep at least one P-E running until 2014 so I could operate the vintage analyzers in my own lab. But stopped running my old chem app on them in 1993 when my employer got their first office PC with Windows 3.1 and GW-Basic. So that was the first actual DOS version of the same old thing, which is the one still in use on my FAT32 partition when I boot to DOS, as well as run from the command line when booted to 32-bit Windows.
When it comes to timestamps a couple old EXEs that have been carried forward on the FAT32 volume are Tetris and Battle Chess from 1989 which I can still run any time since.
That looks like it for files that are actually useful still.