30.1. Introduction to the ARM architecture
The ARM architecture is has been used on the vast majority of mobile phones in the 2010’s, and on a large fraction of micro controllers.
It competes with x86 userland assembly because its implementations are designed for low power consumption, which is a major requirement of the cell phone market.
ARM is generally considered a RISC instruction set, although there are some more complex instructions which would not generally be classified as purely RISC.
ARM is developed by the British funded company ARM Holdings: https://en.wikipedia.org/wiki/Arm_Holdings which originated as a joint venture between Acorn Computers, Apple and VLSI Technology in 1990.
ARM Holdings was bought by the Japanese giant SoftBank in 2016.