A reduced instruction set for ARM processors (based on a 16-bit encoding, instead of 32 bits in standard ARM mode), originally intended for embedded systems with a small amount of RAM. Also for question with the later Thumb2 mixed 16 and 32 bit instruction modes. Consider the tags 'slider' and 'thumbnails' for other meanings of 'thumb'.
This tag is for questions concerning the ARM CPU's operating mode called thumb. Questions about thumb assembly language, interworking between thumb and ARM mode as well as operating system issue in dealing with thumb mode are on topic.
The Thumb instruction set (16 bit only) with restricted use of r8-r15 was later extended to include a mix of 16 and 32 bit instructions. This was called Thumb-2. Thumb-2 is a marketing term. Different CPU families and even specific devices have different instructions. Thumb-2 is fairly meaningless in a technical sense (except it means variable length instructions (always two halfwords) are available along with 16 bit thumb instructions). Thumb-2 at wikipedia
On modern ARM CPUs, Thumb-2 is as rich as the traditional 32-bit mode and much more memory efficient.
For questions related to the scrollbar thumbs consider one of,
- scrollbars
- slider
- seekbar
- etc.
For questions about thumbnails, use the tag thumbnails.
See also: arm cortex-m cortex-a
The paper Profile guided selection of ARM and thumb instructions gives some benchmarking of legacy thumb versus 32 bit modes. Different algorithms are faster in one mode versus the other. The paper is somewhat obsolete as Thumb-2 will be more efficient in modern (2014+) CPUs. Although some deeply embedded devices may only support Thumb.
