Benefits

• Responsiveness --continued execution if part is blocked
• Resource Sharing -- threads shares, easier than share memory or message passing
• Economy --cheaper than process creation, thread switching lower overhead than context switching
• Scalability

• User treads -- managed by user-level threads library
• Kernel threads -- supported by kernel

Model

• Many-to-One
• One-to-One
• Many-to-Many
• to-level model