What is a Multiprogramming Operating System?

In a Multiprogramming Operating System, the CPU can handle multiple tasks at the same time, improving overall system efficiency. How does this happen when the computer has only one CPU? Is the multiprogramming operating system dependent on the number of processors a computer has? With the advancements in technology in the current era, a computer can perform more than one task at the same time. In this article, we will discuss how a Multiprogramming Operating System is used in a computer and how it increases the efficiency of the computer.

Table of Contents:

• What is a Multiprogramming Operating System?
  • Features of Multiprogramming
• Architecture of a Multiprogramming Operating System
• Working of a Multiprogramming Operating System
• Types of Multiprogramming Operating Systems
• Difference Between Multiprogramming and Multitasking Operating Systems
• Importance of Multiprogramming Operating Systems
• Advantages of a Multiprogramming Operating System
• Disadvantages of a Multiprogramming Operating System
• Conclusion

What is a Multiprogramming Operating System?

A Multiprogramming Operating System is a type of operating system that allows several programs to execute concurrently on a single processor, enabling better resource utilization. The process in the CPU has two types of system time: I/O and CPU time. Even though the CPU has only one processor, the operating system is able to quickly switch between the different system times, which appears that all the programs are running at the same time, because of which the CPU utilization is higher, hence it saves time for the processes. For example, you can listen to music and download files from the internet at the same time.

Features of Multiprogramming

Multiprogramming has many features that make it efficient and increase its usage widely. Some of the features of multiprogramming are:

• Single CPU Usage: In a multiprogramming environment, a single CPU is used to manage all the processes, which increases the efficiency of CPU utilization.
• Context Switching: When a process is busy with another task that does not require the CPU’s involvement, the OS quickly switches to another process to save time.
• Reduced Idle Time: Instead of letting the CPU sit idle when one task is waiting for the CPU, multiprogramming keeps it working on another task, which improves system efficiency.
• Better Resource Utilization: As one process is performing a task, the other process is kept in a ready queue to efficiently utilize the resources.

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Architecture of a Multiprogramming Operating System

Now, let us discuss the components of a Multiprogramming OS.

1. Main Memory (RAM)

It is a type of computer memory that stores the temporary data of the running process. In the above diagram, the main memory contains:

• Supervisor: Also known as the Kernel, is the core part of the OS that controls everything, i.e., process scheduling, priority scheduling, memory management, and so on. It stays active in the memory every time, so that the system keeps running smoothly.
• Jobs are the user programs or processes that are loaded into memory.

2. CPU

The Central Processing Unit is the brain of the computer, which is responsible for every small activity the computer performs, and executes one job at a time. This unit performs the arithmetic and logic operations (ALU), fetching and decoding (Control Unit), and also manages the data transfer between the memory unit and I/O devices.

3. Secondary Storage Device

This is the hard disk, SSD, or any third-party storage device that stores the programs that are not present in the memory at that instance. It stores the data to be read or written, and the jobs that are to be removed or saved in the main memory after they are completed. When any program or data needs to be loaded into the main memory, they are loaded from secondary storage.

4. I/O Operations

They are the components that allow a computer system to interact with the outside world. It performs actions like reading a file, writing data to the disk, printing a document, and so on, in multiprogramming systems.

Working of a Multiprogramming Operating System

A Multiprogramming Operating System is used to keep the CPU busy by loading multiple programs into memory and switching between them efficiently, which helps to achieve better performance and resource utilization. Now, let us discuss the working of a multiprogramming OS with the help of the diagram shown in the architecture above.

At the top of the main memory, there is the Supervisor, the core part of the operating system responsible for managing jobs, CPU scheduling, memory, and input/output (I/O) operations.

Below the Supervisor, there are three jobs: Job A, Job B, and Job C. All of them are loaded into the main memory.

• Job B is currently in execution, meaning the CPU is processing it at the moment.
• Job C is in a “Ready” state, waiting for the CPU to become free, and will be scheduled next when the CPU becomes available.
• Job A is performing an I/O operation, such as accessing a storage device, like a hard disk.

Since I/O operations do not require the CPU, it is allocated to other jobs, such as Job B or Job C. The Supervisor handles this coordination by performing context switching, saving the state of one job and loading another, based on job status and availability. If Job B finishes or requests I/O, the Supervisor will switch to Job C.

Once the I/O Job of A is complete, an interrupt signal will be sent to the Supervisor, which will then move Job A to the Ready state. This constant switching and scheduling of jobs ensures that the CPU never becomes idle, resulting in better system efficiency and performance.

Types of Multiprogramming Operating Systems

There are two types of multiprogramming operating systems, as shown below

1. Multiuser Operating System

A multi-user operating system allows multiple users to access a single central computer through separate terminals. The OS switches between users and gives a small portion of the processor time to the different user. This switching is so fast that the user thinks it is a continuous and dedicated access, allowing each user to run the programs independently without any interference. As the number of users increases, the response time of each user will become slower.

2. Multitasking Operating System

A multitasking operating system is a type of multiprogramming operating system that allows two or more programs to run at the same time by switching between them, but only one process is allowed to use the CPU at a particular time. When a program is being used, it is present in the main memory(RAM), but when it is not needed, the OS sends it to the secondary storage so that another process can be brought and executed.

Difference Between Multiprogramming and Multitasking Operating Systems

Below is the difference between Multiprogramming and Multitasking Operating Systems.

Importance of Multiprogramming Operating Systems

A Multiprogramming OS is used in many real-world computer applications, some of which are discussed below.

1. Process Management

A process is a program in execution that is active at that point of time and uses resources like the CPU and I/O devices to perform a task. A multiprogramming operating system is responsible for creating, running, and ending the processes. The OS loads many programs into memory at once and uses these processes one by one as the user uses the system. This is called process management, and it serves as the main part of how the system will operate these processes.

2. Memory Management

Every program that is running in the system needs memory to work. A multiprogramming OS is responsible for handling the memory allocation of each process, i.e., how much memory each process will take, and also ensures that no other process clashes between two processes. Once the process has finished its task and does not need any memory, the OS reclaims that memory and makes it available for other processes.

3. CPU Scheduling

CPU Scheduling is the process by which the operating system selects one process from the ready queue and assigns the CPU for its execution. A multiprogramming OS enables the CPU to schedule more than one process at the same time, while one process is doing its I/O operation. The CPU uses many algorithms, like round-robin, shortest job first, or priority scheduling, to increase its efficiency.

4. Input/Output (I/O) Management

I/O or Input/Output devices are the hardware components that allow a computer system to interact with the outside world. Apart from Memory and CPU, a process also needs devices like the keyboard and printers to complete the process. A multiprogramming OS controls and handles the usage of these I/O devices to avoid bottlenecks and deadlock situations. It also aims that more than one process can perform CPU tasks while another process is doing its I/O operation to maximize the throughput of the system.

5. Inter-Process Communication (IPC)

Inter-Process Communication (IPC) is a mechanism provided by the operating system that allows processes to communicate with each other and synchronize their actions. In a multiprogramming environment, different processes need to exchange their data to synchronize their work efficiently and get the expected output. For example, two processes can use a shared memory to exchange data, and semaphores to prevent both processes from writing it at the same time.

6. Concurrency Control

Concurrency Control is a mechanism in an OS to manage the execution of multiple processes that share the same resources at the same time. In a multiprogramming environment, concurrency control is important to prevent data inconsistency when multiple processes modify the shared data at the same time. It avoids problems like race conditions and deadlocks and ensures that the processes are synchronized properly. For example, by using locks and semaphores on a shared variable or resource, the data will be modified safely.

7. Interrupt Handling

Interrupts are signals sent to the CPU to tell it to stop what it is doing and handle another important process, having high priority. The OS has an interrupt handling system that handles all the interrupts of these signals and responds to them quickly. In a multiprogramming OS, it is important to have a responsive interrupt handling system because the CPU is performing more than one task at the same time, and if a hardware or software interrupt occurs, then it has to be handled efficiently.

Advantages of a Multiprogramming Operating System

The advantages of a Multiprogramming operating system are as follows:

• Better CPU Utilization: While one program waits for an I/O operation, the CPU switches to another program and executes it. Hence, more utilization of the CPU.
• Increases Throughput: As all the processes are executed one after the other, more processes get completed in less time, which increases the overall throughput.
• Reduced Waiting Time: In a multiprogramming system, when one process is waiting for an I/O operation, the CPU does not stay idle, it switches to another process that is ready to run.
• Efficient Use of Resources: In multiprogramming, the computer utilizes its various components, including the CPU, memory, and I/O devices. For example, if one program is waiting for another, then the computer can work on a different program that requires additional resources.

Disadvantages of a Multiprogramming Operating System

The disadvantages of a Multiprogramming operating system are as follows:

• Complex: The switching between the processes uses complex scheduling algorithms like round robin, priority scheduling, etc., hence making it complex.
• Risks of Deadlock: If any two resources are waiting for the same resource for a very long time, a deadlock can occur.
• Security Issues: In a multiprogramming system, many programs run at the same time and share the same memory and resources. This can be risky because one program might accidentally or purposely access another program’s data, which can cause security problems.
• Slow Response: If too many processes are loaded at the same time, switching between the programs will take time, because of the large ready queue.

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Conclusion

From the above article, we concluded that a multiprogramming operating system is a type of operating system that handles multiple processes with the help of one CPU. It has two types, multiuser and multitasking operating systems, both of which increase the performance of the CPU. There are many real-life use cases of multiprogramming operating systems, Concurrency Control, Inter-Process Communication (IPC), CPU Scheduling, and many more. Although multiprogramming is an important idea in operating systems, it should be used carefully, as it can cause performance issues and serious problems like deadlocks.

If you want to learn more about Multiprogramming operating systems in detail, you can refer to our Software Engineering Course.

Multiprogramming Operating System – FAQs