Instruction sets in the Arm architecture
Armv8-A supports three instruction sets: A32, T32 and A64.
The A64 instruction set is used when executing in the AArch64 Execution state. It is a fixed-length 32-bit instruction set. The ‘64’ in the name refers to the use of this instruction by the AArch64 Execution state. It does not refer to the size of the instructions in memory.
The A32 and T32 instruction sets are also referred to as ‘ARM’ and ‘Thumb', respectively. These instruction sets are used when executing in the AArch32 Execution state. In this guide, we do not cover the A32 and T32 instruction sets. To find out more about these instruction sets, see the Related Information section of this guide.