1.3 Middleware

Middleware

• Middleware is software that sits between application programs and the operating system
• Databases, Runtimes, etc

1.5 Multiple Computations on One Computer

Resources

• Limited CPU time, disk access bandwidth, memory bandwidth
• Multiple applications using resources simultaneously

Concurrency

• Make efficient use of resources
• When we aren’t actively using the CPU because we are waiting on I/O, another program can use it

Thread

• Fundamental unit of concurrency
• Sequence of programmed actions
• Each program includes at least one thread

Process

• Container for one or more threads
• Protects threads from interactions from unrelated threads running on the same computer
• Threads in different processes do not share memory

Thread APIs

• Create
• Kill
• Switch

Scheduling

• OS will have many threads that can be run
• Limited CPUs are available
• OS must select thread to run