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How were programs that were written in assembly loaded into memory of 8085 processors? Did the processor come with a bootloader with which you could load information into memory? If so, what did the program look like? In my 8085 simulator I press assemble and and load program and it automatically loads my assembly program into memory. How was this magic done in the original 8085?

Image of my 8085 simulator

Alberto García
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    For use as a microcontroller, or the OS for an old computer, probably by burning to a ROM and wiring it up to the 8085 so the program (or OS kernel) is already in memory when it powers up. If a kernel, it probably has functions to load code from disk or tape as well. – Peter Cordes May 20 '22 at 17:26
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    But in terms of development cycle (edit/build/run), see [Back in the late 1980s, how was commercial software for 8-bit home computers developed?](https://retrocomputing.stackexchange.com/q/9006) on retrocomputing.SE. Systems capable of running an assembler on the computer could just assemble into RAM and run it. Or into a disk file if you had something worthy of being called an OS, and then you could run it. – Peter Cordes May 20 '22 at 17:38
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    Thank you for your answer! Do you know how the program would be loaded into RAM memory? Did the assembler do this? If loaded into a disk file, it would later have to be retrieved and put into RAM to execute the program no? – Alberto García May 20 '22 at 17:53
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    Yes, if you have an OS then the problem of loading files from disk as programs is already solved. If you don't, and it's just an all-in-one IDE with assembler + debugger, then the assembler can just assemble *into* RAM. It's a program running on the machine, and it has to put the resulting machine code somewhere. That somewhere will be an array. See also [How was the first assembler for a new home computer platform written?](https://retrocomputing.stackexchange.com/q/3326) for how those get developed – Peter Cordes May 20 '22 at 17:57
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    Thank you for answering so kindly!!! I think I get the gist of it now. The links you provided were very informational. This is all so interesting!! – Alberto García May 20 '22 at 18:33
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    Back in the day, we used UV erasable EPROMs and later EEPROMS. There would be a tube of blank ones waiting, it wasn't instantaneous but a good moment to get a brew or a comfort break. Also used in-circuit emulators a bit but they were very expensive. My own solution was to make my own emulators running on a PC because the hardware would never be ready until a week before the deadline, and they always blamed any faults on software. The code had to be as bug-free as possible, because we were expected to *prove* that the board was at fault. So we would have self-test verification code ready... – Weather Vane May 20 '22 at 18:56
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    You also wrote an interestig answer here: https://stackoverflow.com/questions/49489376/how-does-assembly-code-actually-get-interpreted-at-the-basic-level – Alberto García May 20 '22 at 19:16

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I actually wrote a full blown application (digital diary) for the 8085 in assembly 35 years ago as my final school project. I had an original IBM XT at the school lab with asm85 assembler. I wrote an entire 6K assembly program in that extremely simple editor and assembled it. The PC was connected to an EPROM programmer via the serial port. I ran a command in DOS that copied the 6K obj file the assembler generated to the EPROM programmer RAM. I installed a 8K EPROM chip to the programmer. The programmer had some keys to operate it so I selected Program at base address 0000h. Obviously my assembly program started at that address so everything worked perfectly. I took the programmed EPROM chip and connected it to a socket on a board I created using ORCAD with a 8156 chip for ports and another chip as an address bus latch. That was a minimum system with another small ram chip and an external 5V power supply. I got a perfect score (100) for the project and it worked until a year ago when I found no use for it anymore and threw it to the garbage bin.

Danny Cohen
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