The Great Symbian

• Thread management done by user-level threads library

• Fast to create and manage threads

• If the kernel is single-threaded, then any user-level thread performing a blocking system call

will cause the entire process to block

• No need for kernel intervention

• Drawback : all may run in single process. If one blocks, all block.

• Examples
- POSIX Pthreads
- Mach C-treads
- Solaris UI-threads