What do you mean by a Process? What are the various possible states of Process? Discuss

A process under Unix consists of an address space and a set of data structures in the kernel to keep track of that process. The address space is a section of memory that contains the code to execute as well as the process stack. The kernel must keep track of the following data for each process on the system:
 
The address space map, 
The current status of the process, 
The execution priority of the process, 
The resource usage of the process, 
The current signal mask, 
The owner of the process, 
A process has certain attributes that directly affect execution, these include: 
PID – The PID stands for the process identification. This is a unique number that defines the process within the kernel. 
PPID – This is the processes Parent PID, the creator of the process.UID – This User ID number of the user that owns this process.
EUID – The effective User ID of the process. 
GID – The Group ID of the user that owns this process. 
EGID – The effective Group User id that owns this process. 
Priority – The priority that this process runs at. 
To view a process you use the ps command. 
 
rlogindThe F field: This is the flag field. It uses hexadecimal values which are added to show the value of the flag bits for the process. For a normal user process this will 30, meaning it is loaded into memory. 
The S field: The S field is the state of the process, the two most common values are S for Sleeping and R for Running. An important value to look for is X which means the process is waiting for memory to become available. 
PID Field: The PID shows the process ID of each process. This Value should be Unique. Generally PID are allocated lowest to highest, but wrap at some point. This value is necessary for you to send a signal to a process such as the kill signal.
PRI field: This stand for priority field. The process with the lowest value in the ‘PRi’ field which has the highest priority. The lower the value, the higher the value. This refer to the process NICE value. It will range form 0 to39. The default is 20, as a process uses the CPU the system will raise the nice value. 
P flag: this is the processor flag. On the SGI this refers to the processor the process is running on. 
SZ field: This refers to the SIZE field. This is the total number of pages in the process. Each page is 4096 bytes. 
TTY field: this the terminal assigned to your process.Time field: the Cumulative execution time of the process in minutes and seconds.COMD field: the command that wat executed.
 
 
What do you mean by a Process? What are the various possible states of Process? Discuss What do you mean by a Process? What are the various possible states of Process? Discuss Reviewed by enakta13 on November 10, 2012 Rating: 5

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