The distinction between RISC and CISC is not a precise one, only a subjective quantitative description.
Reduced Instruction set.
Has few operations, but performs each one very fast.
Takes it to the limit:
https://en.wikipedia.org/wiki/One_instruction_set_computer
Funny example implementation for C in x86 mov: https://github.com/xoreaxeaxeax/movfuscator
Complex instruction set.
Lots of operations.
x86 is considered CISC, although it is known that the processor has a RISC core.
ARM is considered RISC.
The distinction between RISC and CISC is further blurred by the fact that Intel X86, widely condiered CISC is actually composed of:
- a complex instruction decoder, which transforms complex input instructions into a simpler subset called microcode
- a RISC core which understands the microcode and actually runs it