Sequential and Concurrent Program Execution

Characteristics of sequential execution of programs:

1. Sequentiality: The program is executed strictly in steps, and each action starts after the previous action is completed.

2. Closedness: The running environment of the program is only affected by its own actions and is not interfered by external factors.

3. Reproducibility: Under the same initial conditions, the program has the same execution results each time, regardless of the execution speed.

Characteristics of concurrent execution of programs:

1. Intermittency: Concurrently executed programs may restrict each other due to shared resources or task collaboration, forming an intermittent activity mode of "execution-pause-execution".

2. Loss of closure: Concurrent programs share system resources, and the execution speed and control conversion are affected by external factors, resulting in the running environment no longer being closed.

3. Irreproducibility: After losing closure, concurrently executed programs may obtain different execution results under the same initial conditions.