Process and Threads

1. Process

1.1. Program in execution

1.2. instance of running program

1.3. the entity that can be assigned , executed , processor.

1.4. a unit of activity characterized by single sequential thread of execution, a current state , and an associated set of system process

2. Process Element

2.1. Program Code

2.2. Set of data associated with that code

2.3. 8 Process Elements

2.3.1. Identifier

2.3.2. State

2.3.3. Priority

2.3.4. Program Counter

2.3.5. Memory pointers

2.3.6. Context Data

2.3.7. I/O Status Information

2.3.8. Acounting Information

2.4. Control Blocks

2.4.1. Created and managed by OS

2.4.2. Key tool that allows support for multiple process

3. Benefit of Threads

3.1. Takes less time to create a new thread than a process.

3.2. Less time to terminate a thread than a process.

3.3. Threads enhance efficiency in communication between program.

4. Multithreaded Approaches

4.1. A Java run-time environment is an example of a system of one process with multiple threads.

5. Single Threaded Approaches

5.1. A single thread of execution per process, in which the concept of a thread is not recognized.

5.2. MS-DOS

6. Process States

6.1. Trace

6.1.1. sequence of intructiion that execute for that process

6.2. Dispatcher

6.2.1. small program that switches the processor from one process to another.

7. Two-state Process Model

7.1. Running

7.2. Not-running

8. Process Creation

8.1. Process Spawning

8.1.1. when the OS creates a process at the explicit request of another process

8.2. Parent Process

8.2.1. is the original,creating process

8.3. Child Process

8.3.1. is the new process

9. Suspended Processes

9.1. Swapping

9.1.1. Involve moving part of all of a process from main memory to disk.

9.2. Characteristics

9.2.1. The process is not immediately available for execution.

9.2.2. The process may or may not be waiting on an event.