difference between process and program in operating system pdf

Difference Between Process And Program In Operating System Pdf

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In computing, a process is the instance of a computer program that is being executed by one or many threads.

In last article, we have seen what is difference between process and thread. Now , we will talk about what are the differences between process and program used in modern operating systems. Operating system is basically a way to connect the end user to the hardware of the computer.

Operating System - Processes

In computing, a process is the instance of a computer program that is being executed by one or many threads. It contains the program code and its activity.

Depending on the operating system OS , a process may be made up of multiple threads of execution that execute instructions concurrently. While a computer program is a passive collection of instructions typically stored in a file on disk, a process is the execution of those instructions after being loaded from the disk into memory.

Several processes may be associated with the same program; for example, opening up several instances of the same program often results in more than one process being executed. Multitasking is a method to allow multiple processes to share processors CPUs and other system resources. Each CPU core executes a single task at a time.

However, multitasking allows each processor to switch between tasks that are being executed without having to wait for each task to finish preemption.

A common form of multitasking is provided by CPU's time-sharing that is a method for interleaving the execution of users' processes and threads, and even of independent kernel tasks - although the latter feature is feasible only in preemptive kernels such as Linux.

Preemption has an important side effect for interactive processes that are given higher priority with respect to CPU bound processes, therefore users are immediately assigned computing resources at the simple pressing of a key or when moving a mouse. Furthermore, applications like video and music reproduction are given some kind of real-time priority, preempting any other lower priority process.

In time-sharing systems, context switches are performed rapidly, which makes it seem like multiple processes are being executed simultaneously on the same processor.

This simultaneous execution of multiple processes is called concurrency. For security and reliability, most modern operating systems prevent direct communication between independent processes, providing strictly mediated and controlled inter-process communication functionality.

In general, a computer system process consists of or is said to own the following resources:. The operating system holds most of this information about active processes in data structures called process control blocks. Any subset of the resources, typically at least the processor state, may be associated with each of the process' threads in operating systems that support threads or child processes.

The operating system keeps its processes separate and allocates the resources they need, so that they are less likely to interfere with each other and cause system failures e. The operating system may also provide mechanisms for inter-process communication to enable processes to interact in safe and predictable ways. A multitasking operating system may just switch between processes to give the appearance of many processes executing simultaneously that is, in parallel , though in fact only one process can be executing at any one time on a single CPU unless the CPU has multiple cores, then multithreading or other similar technologies can be used.

It is usual to associate a single process with a main program, and child processes with any spin-off, parallel processes, which behave like asynchronous subroutines. A process is said to own resources, of which an image of its program in memory is one such resource. However, in multiprocessing systems many processes may run off of, or share, the same reentrant program at the same location in memory, but each process is said to own its own image of the program. Processes are often called "tasks" in embedded operating systems.

The sense of "process" or task is "something that takes up time", as opposed to "memory", which is "something that takes up space". The above description applies to both processes managed by an operating system, and processes as defined by process calculi.

If a process requests something for which it must wait, it will be blocked. When the process is in the blocked state , it is eligible for swapping to disk, but this is transparent in a virtual memory system, where regions of a process's memory may be really on disk and not in main memory at any time.

Not all parts of an executing program and its data have to be in physical memory for the associated process to be active. An operating system kernel that allows multitasking needs processes to have certain states. Names for these states are not standardised, but they have similar functionality. When processes need to communicate with each other they must share parts of their address spaces or use other forms of inter-process communication IPC.

For instance in a shell pipeline, the output of the first process need to pass to the second one, and so on; another example is a task that can be decomposed into cooperating but partially independent processes which can run at once i. It is even possible for two or more processes to be running on different machines that may run different operating system OS , therefore some mechanisms for communication and synchronization called communications protocols for distributed computing are needed e.

By the early s, computer control software had evolved from monitor control software , for example IBSYS , to executive control software. Over time, computers got faster while computer time was still neither cheap nor fully utilized; such an environment made multiprogramming possible and necessary. Multiprogramming means that several programs run concurrently. At first, more than one program ran on a single processor, as a result of underlying uniprocessor computer architecture, and they shared scarce and limited hardware resources; consequently, the concurrency was of a serial nature.

On later systems with multiple processors , multiple programs may run concurrently in parallel. Programs consist of sequences of instructions for processors. A single processor can run only one instruction at a time: it is impossible to run more programs at the same time. A program might need some resource , such as an input device, which has a large delay, or a program might start some slow operation, such as sending output to a printer.

This would lead to processor being "idle" unused. To keep the processor busy at all times, the execution of such a program is halted and the operating system switches the processor to run another program. To the user, it will appear that the programs run at the same time hence the term "parallel".

Shortly thereafter, the notion of a "program" was expanded to the notion of an "executing program and its context". The concept of a process was born, which also became necessary with the invention of re-entrant code. Threads came somewhat later. However, with the advent of concepts such as time-sharing , computer networks , and multiple-CPU shared memory computers, the old "multiprogramming" gave way to true multitasking , multiprocessing and, later, multithreading.

From Wikipedia, the free encyclopedia. Particular execution of a computer program. Main article: Process management computing. Main article: Process state. Main article: Inter-process communication. See also: History of operating systems. Another technique called simultaneous multithreading used in Intel 's Hyper-threading technology can simulate simultaneous execution of multiple processes or threads.

And, although they have somewhat different terminological histories, they have come to be used as synonyms. Today, the term process is generally preferred over task, except when referring to "multitasking", since the alternative term, "multiprocessing", is too easy to confuse with multiprocessor which is a computer with two or more CPUs.

The Process and the Kernel". Prentice-Hall Inc. Prentice Hall. Parallel computing. Process Thread Fiber Instruction window Array data structure. Multiprocessing Memory coherency Cache coherency Cache invalidation Barrier Synchronization Application checkpointing. Stream processing Dataflow programming Models Implicit parallelism Explicit parallelism Concurrency Non-blocking algorithm.

Automatic parallelization Deadlock Deterministic algorithm Embarrassingly parallel Parallel slowdown Race condition Software lockout Scalability Starvation. Category: Parallel computing. Operating systems. Disk operating system Distributed operating system Embedded operating system Mobile operating system Network operating system Object-oriented operating system Real-time operating system Supercomputer operating system.

Device driver Loadable kernel module Microkernel User space. Fixed-priority preemptive Multilevel feedback queue Round-robin Shortest job next. Authority control GND : Categories : Process computing Concurrent computing Operating system technology. Namespaces Article Talk. Views Read Edit View history. Help Learn to edit Community portal Recent changes Upload file. Download as PDF Printable version. GND :

Operating system

Management tasks include scheduling resource use to avoid conflicts and interference between programs. Unlike most programs, which complete a task and terminate, an operating system runs indefinitely and terminates only when the computer is turned off. One form of multiprocessing is called time-sharing , which lets many users share computer access by rapidly switching between them. This virtual memory both increases the address space available to a program and helps to prevent programs from interfering with each other, but it requires careful control by the operating system and a set of allocation tables to keep track of memory use. Perhaps the most delicate and critical task for a modern operating system is allocation of the CPU; each process is allowed to use the CPU for a limited time, which may be a fraction of a second, and then must give up control and become suspended until its next turn. Switching between processes must itself use the CPU while protecting all data of the processes.


Program contains a set of instructions designed to complete a specific task. Process is an instance of an executing program. Program is a passive entity as it resides in the secondary memory. Process is a active entity as it is created during execution and loaded into the main memory.


What is a Process?

A process is a program in execution. Process is not as same as program code but a lot more than it. A process is an 'active' entity as opposed to program which is considered to be a 'passive' entity. Attributes held by process include hardware state, memory, CPU etc. There is a Process Control Block for each process, enclosing all the information about the process.

The main difference between program and process is that a program is a set of instructions that allows the CPU to perform a certain task while a process is a program in execution. The operating system is the interface between the user and the hardware. The core of the operating system is the kernel. It performs multiple important tasks such as memory management, process management, file handling, IO device handling and many more.

Program : When we execute a program that was just compiled, the OS will generate a process to execute the program.

Difference between process and program

A program and a process are related terms. The major difference between program and process is that program is a group of instructions to carry out a specified task whereas the process is a program in execution. While a process is an active entity, a program is considered to be a passive one. There exist a many-to-one relationship between process and program, which means one program can invoke multiple processes or in other words multiple processes can be a part of the same program. Basis for comparison Program Process Basic Program is a set of instruction. When a program is executed, it is known as process. Nature Passive Active Lifespan Longer Limited Required resources Program is stored on disk in some file and does not require any other resources.

Difference between a process and a program A process invokes or initiates a program. It is an instance of a program that can be multiple and running the same application. Example:- Notepad is one program and can be opened twice. They are separate loadable modules. Where as the program perform the tasks directly relating to an operation of a user like word processing, executing presentation software etc.

Process (computing)

A program is an executable file which contains a certain set of instructions written to complete the specific job on your computer. For example, Google browser chrome. Programs are never stored on the primary memory in your computer. Instead, they are stored on a disk or secondary memory on your PC or laptop.

A process is basically a program in execution.

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