On a resource and computing-power constrained system used for a very specific function it would not be too far off if one said something like that(with caveats)

On a resource and computing-power constrained system used for a very specific function it would not be too far off if one said something like that(with caveats). Anything past that category and he would be dead wrong. In other words, if you only have 2K or RAM to play with, a limited stack depth, a CPU clock of, say, 12MHz and a 12 clock instruction cycle you have no choice but to get very clever. Pushing and popping a bunch of registers on every function call could rob you of much needed performance and resources. In fact, on such a system that alone could cause unintended side effects and introduce potential safety issues (talking real-time systems with a requirement for deterministic response). You could also have a situation where you overflow the stack and things go from bad to worst very quickly. BTW, this, among other things, is one of the reasons I abandoned such small, 8-bit, resource-constrained architectures for most embedded projects a long time ago. The 8051 derivatives (Silicon Labs) have always been some of my favorites. I might still use them for small projects such as small control panels or simple sensor pre-processing. These days you can buy 32 bit processors running in the tens to hundreds of MHz for $10 or less. These provide you with the ability to write "proper" embedded software with all the luxuries of greatly increased resources and operating speed.