Process in Operating System: Components and Life Cycle

Ans. Scheduling governs the order in which tasks are performed and is managed by a set of guidelines and procedures. The system software includes the scheduling program known as the scheduler, and the algorithm it utilizes is called the scheduling algorithm.

Several factors or traits that help in creating an effective scheduler include:

• CPU Use – To ensure maximum CPU utilization, it is essential to design an efficient scheduling technique. The CPU should be utilized effectively.
• Throughput - The volume of work finished in a unit of time is referred to as throughput. In simpler terms, throughput is the relationship between the number of finished tasks per unit of time and the executed procedures. To optimize the number of jobs processed per time unit, it is necessary to utilize the scheduling method.
• Response time - In technical contexts, response time signifies the latency to start answering a request. An interactive user's reaction time should be as quick as possible for a scheduler.
• Waiting time - When multiple jobs are fighting for resources in a multiprogramming system, this period of time is known as the waiting period. Efforts should be made to minimize the waiting time.

Ans. Shortest Remaining Time, sometimes known as SRT, is an anticipatory planning method. In SRT, all processes including newly arrived ones are scheduled to run after the process with the least remaining runtime. In SRT, a newly created process with a shorter expected run time may replace a running process. It manages sporadic cancellations and keeps track of the operating process's elapsed service time.

Ans. Multiprogramming has various benefits.

• Multiprogramming organizes a lot of tasks such that the CPU always has one to complete, increasing CPU utilization.
• Higher throughput is the total number of programs that are performed in a given amount of time. Throughput is higher in multiprogramming because the CPU does not wait for I/O for the program it is now running.
• Shorter Turnaround Time Multiprogramming significantly reduces the turnaround time for small jobs.
• Multiprogramming allows for better main memory utilization because multiple programs can run simultaneously. Memory is thus used to its full potential.
• Multiprogramming results in a better degree of resource utilization since numerous programs are actively contending for resources.
• Multiple users are supported by multiprogramming.

Ans. If the speed of the CPU and the I/O devices are roughly equal, the buffering aids in having them both operate at maximum speed so that neither device ever has a chance to become idle.

The C.P.U. is typically significantly quicker than an input device. In this situation, the Central Processing Unit (CPU) consistently encounters an empty input buffer and eagerly awaits the input device to read a record into the buffer. When it comes to output, the C.P.U. keeps running at maximum speed until the output buffer is filled, at which point it begins to wait.

As a result, workloads that balance computational effort and I/O operations benefit from buffering. Other situations might result in buffering scheme failure.

Ans. The usage of multiple processors in close coordination is supported by multiprocessing operating systems or parallel systems.

Here are several advantages of a multiprocessing system:

• Increased Throughput: The multiplication of processors allows for accomplishing more tasks within a specified timeframe, leading to increased productivity.
• Saving money: Parallel systems exhibit resource sharing of peripherals, buses, and memory. Hence, choosing multiprocessor systems is a cost-effective decision when compared to deploying multiple single systems. Additionally, it is less expensive to store data on a single disc that is shared by all processors when several programs need to access the same data than it is to use multiple copies of the same data.
• Increased dependability: This system has increased dependability since the workload is spread among numerous processors. Even though the system may operate more slowly if one of the processors breaks, it will still function properly.

Ans. The computer system's operating system is a necessary component, to be precise. Computer hardware is nothing more than an idle electronic device without an operating system, making it difficult for the user to execute programs.

Due to the fact that only machine language is understood by computer hardware. Every program must be written in machine language, which is tough to do.

Therefore, it would be very challenging to run user programmes or address user issues without an operating system.

Ans. In time-sharing systems, time slicing is a scheduling method or process. A different name for it is round-robin scheduling. Giving all processes an equal chance to consume CPU is the goal of Round Robin scheduling or time-slicing scheduling. Slices of CPU time are broken up and assigned to prepared processes in this sort of scheduling.

• One-time quantum may be used to complete brief processes. Numerous quanta may be needed for lengthy processes.
• The effectiveness of the time-slicing policy is heavily influenced by both the size and duration of the time quantum.
• The Round Robin policy turns into an FCFS policy when the time quantum is quite large. 
• Insufficient quantum size leads to excessive context/process transitions, causing a decline in CPU performance. Therefore, the selection of time quanta is a crucial design choice.
• A certain amount of time is needed to save and load registers, update various tables and lists, etc. during the process-switching operation.

Ans. All current computers are capable of performing multiple tasks at once. A computer, for instance, may be executing a user program while reading from a disc and printing to a printer. The CPU alternates between programs in a multiprogramming system, running each one for a brief period of time.

• Despite the fact that the CPU only ever has one program executing at once. Because of the high CPU speed, many programs can run simultaneously.
• It provides the user with the impression that numerous processes are running concurrently.
• Pseudo parallelism is the phrase for this quick switching of the CPU between programs, which creates the appearance of parallelism.
• The creators of operating systems have developed a process model to make dealing with parallelism easier because it is quite challenging to keep track of numerous, concurrent tasks.

The process model

All of the computer's software that can be run, including the operating system, is arranged into a series of processes in the process model. A process is just an active program that contains the register, counter, and variable values at the time of execution.

It is assumed that each process has its own virtual CPU. The actual CPU alternates between different processes. It is convenient/easier to imagine a group/number of processes operating in (pseudo) parallel in order to track CPU changes across programs. In actuality, multiprogramming is what is happening with the quick switching.

Ans. First fit

The first fit strategy assigns the first available partition or hole that is large enough to accommodate the process. The first eligible free division is where it ends.

Best fit

The best-fit strategy involves assigning the smallest available partition that meets the demands of the requesting process. This algorithm looks through the whole list of available partitions first, then takes into account the smallest hole that is suitable. It next tries to locate a hole that is close to the required process size.

Worst fit

The greatest free section should be found using the poorest fit approach so that the remaining portion will be large enough to be useful. The opposite is true for the ideal fit strategy.

Buddy’s system

Sizes of free blocks in the buddy system are expressed as integral powers of 2, such as 2, 4, 8, 16, etc. up to the size of the memory. A free block from the available list of free blocks of size 2k is allocated when a free block of size 2k is requested. If a free block of size 2k is not available, the request is satisfied by splitting the block of size 2k+1 into two pieces known as friends.

Next fit

A modified version of the first fit is the next fit. Finding a free partition is the first step in the process. The next time it is called, the search resumes where it left off rather than from the beginning.

Ans. If a page requested for execution in the demand paging memory management technique does not exist in the main memory, a page fault occurs. A free page frame is identified and allocated in the main memory in order to load the requested page there. If no page frame is available, the memory manager must free a frame by moving its contents to secondary storage in order to make space for the needed page. Numerous plans or techniques are employed to change pages.