> For the complete documentation index, see [llms.txt](https://liuyang89116.gitbook.io/operating-system/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://liuyang89116.gitbook.io/operating-system/summary_ch3.md).

# Summary ch3

1. **Process Concept:**  

   (1)The program code, also called **text section**  

   (2)Current activity context including **program counter**, processor registers  

   (3)**Stack** containing temporary data  

   (4)**Data section** containing global variables  

   (5)**Heap** containing memory dynamically allocated during run time  
2. **Process state:**  

   (1)**new**: The process is being created  

   (2)**running**: Instructions are being executed   

   (3)**waiting**:  The process is waiting for some event to occur   

   (4)**ready**:  The process is waiting to be assigned to a processor  

   (5)**terminated**:  The process has finished execution
3. **Process Control Block (PCB):**  

   (1)Each process is represented by a PCB  

   (2)Created and managed by the operating system  

   (3)Contains the process elements  
4. **When to switch process:**  

   (1)Clock interrupt  

   (2)I/O interrupt  

   (3)Memory fault  

   (4)Trap  

   (5)System call
5. **Context switch:** When CPU switches to another process, the system must save the state of the old process and load the saved state for the new process via a context switch
6. **interprocess communication (IPC)**  

   (1)Shared memory  

   (2)Message passing