Micro.blog May 2022 Photoblogging Challenge Day 1 📷: switch
Imagine programming this computer through switches!
@dfj I started my programming career on an old PDP-8 (transistors not chips, and core memory) and every time that I crashed it I had to toggle the bootstrap loader back in through the front-panel (about 16 12-bit numbers). The switches were nearly worn out and sometimes had to be flipped a few times to get a bit set to '1'. It was a great incentive to really check your code carefully before running it.
@frogplate Wow! That’s an incredible story! Must have been fun (but also sounds tedious) to have been working with these early computers.
@dfj It was incredibly fun! Our PDP-8 was in three or four cabinets and had (I think) 12 kwords of memory, and a teletype for the console. I really got a kick out of seeing my programmes flashing away on the front-panel lights. Nowadays I build groups of services that run in dozens of Docker containers on a remote web farm, and it is still exciting... but not quite so fulfilling as flipping the switches on the front-panel yourself.
@dfj Just seen your bio... So the other fun thing about the PDP-8 was that it was one of the last architectures to have no hardware support for a software stack - there were no stack pointer register. Instead when you called a subroutine it had to store the return address in the first word of its own code. This made writing recursive code really interesting...
@frogplate hah, wild to me! I learned about these aspects of cpu architecture in college but have always worked professionally at a higher level, so I never had to consider these things. Similar to you, I’m working with Docker and web services day to day.
@frogplate Nothing like blinking lights and switches to make it tactile and feel real!
I’ve only tinkered around with mobile development, but having something run in the palm of your hands and being able to “touch” it through the screen does have a satisfaction to it.
@sod I'm not entirely sure that it did reduce hardware cost as a stack would have allowed the code to be a bit more dense, and memory cost was a significant part of the price of machines in that era. The PDP-8 was a cut-down version of the PDP-5 from the early 60's and that didn't have a stack register. But DEC introduced stacks in the PDP-6 (I think). So it might have just been pragmatic to cut-down and re-use the PDP-5 architecture without the design cost of squeezing in the extra register and instructions.