{"id":99909,"date":"2021-08-03T09:00:21","date_gmt":"2021-08-03T03:30:21","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=99909"},"modified":"2021-07-30T14:46:44","modified_gmt":"2021-07-30T09:16:44","slug":"processes-in-operating-system","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/processes-in-operating-system\/","title":{"rendered":"Processes in Operating System"},"content":{"rendered":"

The program being executed by an operating system is a process. It takes place in a sequence and is the basic unit of work to be implemented in the system. A program during execution becomes a process and performs all the tasks for the user.<\/p>\n

Sections of a Process in OS<\/h3>\n

A process has four sections. These sections are as follows:<\/p>\n

1. Stack:<\/strong> This has temporary data like return address and local variables.<\/p>\n

2. Heap:<\/strong> This is the memory allocated to a process dynamically, during its run time.<\/p>\n

3. Text:<\/strong> This consists of the ongoing activity of a process that is represented by the value of the Program Counter and the contents of the processor’s registers.<\/p>\n

4. Data:<\/strong> This has global and static variables.<\/p>\n

\"Sections<\/a><\/p>\n

Different times concerning a process in Operating System<\/h3>\n

1. Burst time:<\/strong> The time required for the execution of the process<\/p>\n

2. Arrival time:<\/strong> The time at which the process enters the ready queue.<\/p>\n

3. Turnaround time:<\/strong> The time taken by a process from entering the ready state for the first time till its exit time i.e., the difference between completion time and arrival time.<\/p>\n

4. Waiting time:<\/strong> The time spent by the process in ready state i.e., the difference between turnaround time and burst time.<\/p>\n

5. Exit time:<\/strong> The time at which the process completes execution and exits the system.<\/p>\n

6. Response time:<\/strong> The time taken by a process, to be allocated to the CPU, for the first time after entering ready queue i.e., the difference between the time a process first gets CPU and the arrival time<\/p>\n

7. Throughput:<\/strong> This is a way to find the efficiency of a processor. It is the number of processes executed by the CPU in a given amount of time.<\/p>\n

Program<\/h3>\n

Program is a part of a code. It can be of any length from a single line to millions of lines. A computer programmer or coder is responsible for writing a program. It is a set of instructions written to perform specific tasks for the user. Following is a simple example of a program in the C programming language:<\/p>\n

#include <stdio.h>\r\n\r\nint main() {\r\n   printf(\"DataFlair \\n\");\r\n   return 0;\r\n}\r\n<\/pre>\n
We can say that a process is a dynamic instance of a program. The secondary storage stores a program. This program converts into a process during execution. Software is a collection of computer programs, libraries, and related data.<\/p>\n
Process vs Program in OS<\/h3>\n
The following table shows the difference between a process and a program.<\/p>\n\n\n\n\n\n\n\n\n
Process<\/strong><\/td>\nProgram<\/strong><\/td>\n<\/tr>\n
An instance of a program being executed.<\/span><\/td>\nA collection of instructions written to perform a specific task for the user.\u00a0<\/span><\/td>\n<\/tr>\n
Short lifetime<\/span><\/td>\nLong lifetime<\/span><\/td>\n<\/tr>\n
Requires resources such as memory, CPU, I\/O devices, etc…<\/span><\/td>\nStored in hard-disk and doesn\u2019t requires any resources<\/span><\/td>\n<\/tr>\n
Has a dynamic instance of code and data<\/span><\/td>\n Has static code and data.<\/span><\/td>\n<\/tr>\n
Running instance of code<\/span><\/td>\n Executable code<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Process Life Cycle in OS<\/h3>\n
During execution, a process has to go through multiple states. Though these states and their names differ in different operating systems, the following are the common states of the process life cycle:<\/p>\n
1. Start:<\/strong> The initial state of a process when it is first created.<\/p>\n
2. Ready:<\/strong> In this state, the process is ready to be assigned to a processor and waits for the OS to allocate the processor to it. A process can come into this state multiple times especially when the scheduler assigns the CPU to another process.<\/p>\n
3. Running:<\/strong> After being assigned to a processor, the process enters into the running state and the processor executes its instructions.<\/p>\n
4. Waiting:<\/strong> If another process occupies the resource required by the running process, the running process moves into a waiting state.<\/p>\n
5. Terminated or Exit:<\/strong> A process moves to this state when an OS terminates it, or after it finishes execution and waits to be removed from the main memory.<\/p>\n
Process Control Block (PCB) in OS<\/h3>\n
A data structure retained by the OS for each process is known as a process control block. Each PCB has its own integer process ID (PID) which is the identity of the PCB. PCB is a collection of all the information regarding a process like the state of the process, location of a process, etc. The lifetime of a PCB is as long as that of a process i.e., till the OS terminates a process.<\/p>\n
Following is the information that PCB keeps a track of:<\/p>\n
1. Process State:<\/strong> This is the current state of the process. It can be any state then, ready, running, waiting, or any else.<\/p>\n
2. Process privileges:<\/strong> This allows\/disallows access to system resources.<\/p>\n
3. Process ID:<\/strong> This is the unique identification of a process like aadhar card for us.<\/p>\n
4. Pointer:<\/strong> It is a pointer to the parent process.<\/p>\n
5. Program Counter:<\/strong> This points to the address of the next instruction that is to be executed for a process.<\/p>\n
6. CPU registers:<\/strong> This is where a process is stored before execution or entering the running state.<\/p>\n
7. CPU Scheduling Information:<\/strong> Stores process priority and other scheduling information necessary for scheduling a process.<\/p>\n
8. Memory management information:<\/strong> This contains page table information, memory limits, and segment table based on the memory used by the operating system.<\/p>\n
9. Accounting information:<\/strong> Stores information regarding the amount of times a processor is used for process execution, time limits, execution ID, etc.<\/p>\n
10. I\/O status information:<\/strong> The list of I\/O devices allocated to the process is stored here.<\/p>\n
\"Process<\/a><\/p>\n
CPU-Bound vs I\/O-Bound Processes<\/h3>\n
The process of CPU-bound needs more CPU time i.e., it spends more time in the running state. Whereas the process of I\/O-bound needs more I\/O time and less CPU time i.e., it spends more time in the waiting state.<\/p>\n
Process Scheduling in OS<\/h3>\n
A process is the basis of computation. A process is a lot more than a program code. It is a program in execution. A process has four sections, namely, text, data, heap, and stack. We will discuss process scheduling and its types in detail in the next segment.<\/p>\n
Summary<\/h3>\n
A process is an instance of a running program. There are four sections of a process stack, heap, text, and data. There are five states in a process, namely, new, ready, running, waiting, and termination. Every process has its own PCB that keeps track of all the information related to a process like a process ID, process state, pointer, priority, program counter, CPU register, I\/O information, accounting information, and much more.<\/p>\n","protected":false},"excerpt":{"rendered":"
The program being executed by an operating system is a process. It takes place in a sequence and is the basic unit of work to be implemented in the system. A program during execution...<\/p>\n","protected":false},"author":1,"featured_media":99919,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24565],"tags":[24885,24883,24884,24888,24887,24886,24882],"class_list":["post-99909","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-operating-system-tutorials","tag-cpu-bound-vs-i-o-bound-processes","tag-operating-system-processes","tag-process-control-block-in-os","tag-process-in-os","tag-process-life-cycle","tag-process-scheduling-in-os","tag-processes-in-operating-system"],"yoast_head":"\nProcesses in Operating System - DataFlair<\/title>\n<meta name=\"description\" content=\"Process in OS is an instance of a running program. 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