Development of the Arm architecture
The Arm architecture is developed over time and each version builds on what came before.
You will commonly see the architecture referred to as something like:
This means Version 8 of the architecture, for A-Profile.
Or, in short form:
This figure shows the development of the Arm architecture from version 5 to version 8, with the new features that were added each time. In this guide, we will only look at Armv8-A.
Armv8-A was a major milestone for Arm. Up to and including Armv7-A/R, the Arm architecture was a 32-bit architecture. Armv8-A is a 64-bit architecture, although it still supports 32-bit execution to provide backwards compatibility for legacy software (for example, v7, v6, and v5).
We will not discuss all the features listed on the diagram here, but we will introduce them in later topics.