Introduction
Multitasking and multiprogramming are two fundamental concepts in the domain of concurrent computing, each playing a distinctive role in managing processes and enhancing system efficiency. While both involve the execution of multiple tasks, they differ in their core objectives, mechanisms, and application scenarios. Understanding the nuances between multitasking and multiprogramming is crucial for designing robust operating systems and optimizing resource utilization.
What is Multiprogramming?
In simple words, Multiprogramming provides multiple users to perform different tasks on a single processor at the same time. It is non-preemptive where once resources (CPU cycles) are assigned to a process, the process retains control of the CPU until it is terminated or enters a waiting state. However, if a running process requests I/O or an external interrupt during the process’s execution, the CPU will then stop that running process and move to that specific interrupt.
- The basic idea behind it is to use the processor efficiently and reduce the ideal time of the processor.
- It creates multiple ready-to-run processes for different users. If one process stalls for some reason, then the operating system can execute the other processes available in the queue.
- The multiprogramming operating system facilitates the whole process in such a way that the CPU utilization is the maximum so that the processor’s idle time can be reduced.
In the example given below, P3 will wait until the P2 is completed with the execution.
Let’s look at an example:
Let’s suppose there are five Processes P1, P2, P3, P4, and P5 with their execution time 10, 15, 5, 25, and 2 ms respectively. Then P1 completely executes from time 0-10. Then P2 executes from time 10-25. Then P3 will execute from a 25-30 time period. Then P4 will execute from 30-55. And at last, P5 will execute from 55-57. Keep in mind there is no interrupt occurring during the execution of these processes. If it happens, then the CPU moves to that particular interrupt.
Advantages of Multiprogramming
- Because there is less context switching, the CPU never becomes idle, resulting in maximum utilization.
- Because non-preemptive is used, memory and resources are readily handled.
- It can accommodate many users.
- Short-term jobs are executed sooner than long-term jobs.
Disadvantages of Multiprogramming
- Response time is reduced.
- Due to non-preemption, long-term jobs must wait a long time to be completed.
- Managing all processes might be problematic at times.
Multitasking
Definition and Purpose: Multitasking refers to the concurrent execution of multiple tasks or processes on a single processor. The primary goal is to maximize CPU utilization, allowing users to run multiple applications simultaneously. Multitasking is common in modern operating systems and is essential for providing a seamless user experience.
Mechanism: In multitasking, the CPU rapidly switches between different tasks, giving the illusion that multiple programs are executing simultaneously. This is achieved through time-sharing, where each task is allocated a small time slice for execution before moving to the next task. Common examples of multitasking include running a word processor, web browser, and media player concurrently on a computer.
Use Cases: Multitasking is prevalent in personal computers, smartphones, and other devices where users expect to run multiple applications concurrently. It enhances user productivity and allows efficient utilization of system resources.
Multiprogramming
Definition and Purpose: Multiprogramming involves the simultaneous execution of multiple programs by a computer system. The primary objective is to keep the CPU busy at all times by loading and executing programs in the memory. This helps in minimizing CPU idle time and maximizing throughput.
Mechanism: In multiprogramming, several programs are loaded into the memory simultaneously. The CPU scheduler selects a program from the ready queue, and when it is interrupted or needs to wait for an I/O operation, the control shifts to another program. This overlapping of CPU and I/O operations ensures that the CPU is constantly engaged.
Use Cases: Multiprogramming is commonly used in batch processing systems and time-sharing systems. It is effective in scenarios where a mix of CPU-bound and I/O-bound processes need to be executed concurrently to achieve optimal system performance.
Difference Between Multitasking And Multiprogramming
| Parameter | Multiprogramming | Multitasking | |
| Definition | Multiple programs are loaded into memory simultaneously. | A single program is loaded into memory and divided into multiple tasks or threads. | |
| Switching | Switching between programs is done by the operating system. | Switching between tasks is done by the operating system or by the program itself. | |
| Algorithm | Programs are scheduled based on their priority or in a round-robin fashion. | Tasks are scheduled based on their priority or using preemptive or non-preemptive scheduling algorithms. | |
| Use case | Used in batch processing and time-sharing systems. | Used in desktop computing and server applications. | |
| Basic advantage | Maximizes resource utilization by minimizing idle time. | Allows multiple tasks to run concurrently to improve system responsiveness. |
Key Differences
- Objective:
- Multitasking: Aims to maximize user productivity by allowing the simultaneous execution of multiple user-level tasks.
- Multiprogramming: Focuses on maximizing CPU utilization by keeping the processor busy with the execution of multiple programs.
- Resource Allocation:
- Multitasking: Involves time-sharing and quick switching between tasks to provide the illusion of concurrent execution.
- Multiprogramming: Requires the loading of multiple programs into memory, allowing the CPU to execute instructions from different programs in overlapping fashion.
- User Interaction:
- Multitasking: Geared towards providing a responsive user interface, allowing users to interact with multiple applications concurrently.
- Multiprogramming: Often operates in the background without direct user interaction, ensuring optimal system throughput.
Comparison Chart Difference Between Multitasking And Multiprogramming
| Criteria | Multitasking | Multiprogramming |
| Objective | Maximize user productivity | Maximize CPU utilization |
| Resource Allocation | Time-sharing, quick task switching | Loading multiple programs in memory |
| User Interaction | Responsive user interface | Background operation, less user-facing |
| Common Examples | Running multiple applications on a computer | Batch processing systems, time-sharing systems |
Use cases of Multitasking
- Desktop computing: Multitasking is a common use case for desktop computing, where users may want to run multiple applications or tasks simultaneously, such as browsing the web, listening to music, and editing a document simultaneously.
- Server applications: Multitasking is also an important feature of server applications, where multiple tasks or processes may need to be run concurrently to handle incoming requests or data streams.
- User Interface: The computers nowadays have graphical user interface (GUI) that allows users to seamlessly switch between different applications and tasks. For example, users can open and switch between multiple windows and tabs in their web browser. No need to close or minimize them.
Conclusion
In essence, while multitasking and multiprogramming share the overarching goal of concurrently handling multiple tasks, they diverge in their primary objectives, mechanisms, and application scenarios. Multitasking prioritizes user experience and responsiveness, allowing users to interact with various applications simultaneously. On the other hand, multiprogramming focuses on optimal resource utilization, keeping the CPU occupied by executing multiple programs concurrently. Both concepts play pivotal roles in the design and functionality of modern operating systems, catering to diverse computing requirements.
