The key idea behind 16-BIS is that of a super-reduced instruction set. Essentially, the ARM926EJ-S processor has two instruction sets:
• ARM mode or 32-BIS: the standard 32-bit instruction set
• Thumb mode or 16-BIS: a 16-bit instruction set
The 16-bit instruction length (16-BIS) allows the 16-BIS to approach twice the density of standard 32-BIS code while retaining most of the 32-BIS’s performance advantage over a traditional 16-bit processor, using 16-bit registers. This is possible because 16-BIS code operates on the same 32-bit register set as 32-BIS
code. Additionally, 16-bit code can provide up to 65% of the code size of the 32-bit code and 160% of the performance of an equivalent 32-BIS processor connected to a 16-bit memory system.

16-BIS的关键点是超精简指令集。实质上，the ARM926EJ-S处理器有两套指令集：
---ARM模式或者32-BIS：标准32-bit指令集
---Thumb模式或者16-BIS：16-bit指令集

下面的帮忙翻译一下 自己组织不好语言 谢谢