Multiprogramming was a key feature introduced in third-generation operating systems, where multiple programs could reside in memory and share the CPU. The third-generation operating systems were well suited for big scientific calculations and massive commercial data processing runs; they were still basically batch systems.
Multiprogramming is different from batch processing in that the CPU is kept busy at all times. Every process needs two types of system time—CPU time and IO time. It allows a single processor to run a number of programs at once; it waits for I/O operations while other programs run, and the CPU switches to the second one if one or both of them are ready to run.
In this blog, we will look more into the multiprogramming operating system, its meaning, features, types, working and disadvantages and advantages. Let’s explore more about it.
Using a single-processor machine, a multiprogramming operating system can run various programs. In this multiprogramming os if one program has to wait for an I/O operation, other programs use the CPU in the meantime. Multiprogramming was the foundational approach that allowed multiple programs to run on a single CPU system. As a result, various jobs may have to share CPU time.
Moreover, their jobs are not scheduled to be completed at the same time. These operating systems played a foundational role in the evolution of modern operating systems. Modern OSs like Linux, Windows, and iOS integrate multiprogramming but are better categorized as multitasking and multiprocessing OSs. However, multiprogramming operating systems are designed to store and process various programs simultaneously; it is not necessary in real time. When software is run, it is referred to as a task, process, or job.
When several programs run at once, the system avoids wasting time and uses the CPU, memory, and other resources more effectively. This results in better performance than systems that process one task at a time. One of the main aims of multiprogramming is to manage the different resources of the entire system. There are various core components to manage multiprogramming systems concurrently, like the file system for managing files, the transient area, the memory manager, the command processor, and the I/O control system.
Now, let's look at an example of how a multiprogramming operating system works. The solution given below was to partition memory into different pieces, with various jobs in each partition as shown in the diagram. One job was waiting for I/O to complete; another job could be using the CPU. The CPU could be kept busy all the time if enough jobs could be held in the main memory at once.
Having multiple jobs safely in memory at once needs special hardware to protect each job against snooping and mischief by the other ones. Whenever a running job is finished the operating system can load a new job from the disk into the now-empty partition and run it. This process is part of job management and swapping. Separately, spooling was used to manage I/O devices by queuing output jobs on disk.
Some examples of multiprogramming operating systems that have been widely used across different computing environments include IBM OS/360, UNIX, VMS, Windows NT, Linux, macOS, and HP-UX. The latest example for Android, iOS, and other mobile operating systems on phones is that one can listen to music and, on the other hand, also send/receive text messages.
We had discussed the meaning of multiprogramming operating systems; now it's time to have a look at the features of multiprogramming operating systems.
Memory allocation and deallocation for multiple processes running all together are the responsibilities of a multiprogramming OS. Techniques like virtual memory, paging, and segmentation are used to optimise memory usage, and reduce fragmentation and improve system performance. Within a multiprogramming OS memory, management controls the allocation and deallocation of memory for simultaneous processes to ensure efficient execution.
To optimize memory usage techniques like paging, segmentation, and virtual memory allow processes to use more memory than is physically available, ensuring enough space for execution. These techniques help manage or reduce memory fragmentation in many cases, which can improve memory efficiency and system performance.
The operating system is responsible for allocating CPU time to various processes using scheduling algorithms. To ensure a fair and efficient resource use, algorithms such as round robin, shortest job first, and priority scheduling are used.
CPU scheduling ensures efficient use of the CPU by selecting and switching between processes for execution. In order to maximise system performance these algorithms look to distribute CPU time fairly and effectively.
This type of OS is designed to support multiple users at the same time. It can run various applications together maintaining responsiveness and stability under normal workloads.
Modern operating system built on multiprogramming principles, allow users to run multiple programs simultaneously, like games, Microsoft PowerPoint, Excel, and others applications.
I/O management in the operating system aims to handle input/output operations efficiently to prevent process blocking and enable smooth execution of I/O tasks.
In those cases, I/O management schemes that use various techniques like buffering, caching, and device scheduling have been developed to deal efficiently with input/output operations. Caching, buffering, and scheduling of I/O operations help minimise latency and maximise throughput, contributing to higher I/O bandwidth.
In a multiprogramming system, multiple programs are stored in memory, and each running instance is treated as a separate process with its own memory space. The operating system handles all these processes and their states. This technique ensures better CPU utilisation, as the CPU is always working unless no processes are available.
The operating system selects a process from the ready queue using a scheduling algorithm to determine which one will execute next. If a running process requests i/o, it is moved to a waiting state, and the CPU is assigned to another ready process. In memory-constrained systems a waiting process may be swapped to secondary storage to free up memory, allowing the CPU to continue with another ready process.
Once the I/O operation is complete, the process is moved back to the ready queue and is scheduled to run again. Even on a single-processor system, multiple programs can run concurrently through time-sharing, keeping the CPU active most of the time.
The following are the two kinds of multiprogramming operating systems
A multitasking operating system allows multiple applications to run concurrently by quickly switching between them, giving the illusion of simultaneous execution. When memory is limited, the operating system may temporarily move inactive programs to secondary storage, loading them back when needed.
When a program is switched out of memory, it is saved on the disk temporarily to be retrieved only when needed again. Operating systems that support multitasking better manage hard disks and virtual memory. By quickly switching between tasks, multitasking reduces idle CPU time and improves overall processing efficiency.
A multiuser operating system enables multiple users to share the processing power of a central computer through different terminals. The operating system achieves this by quickly switching between active user processes or sessions. Each of these is allotted a certain amount of processor time on a central computer. Because the operating system switches between user processes so rapidly, each user experiences what seems like constant access to the central computer.
The operating systems rapidly cycle through user sessions, giving the illusion that each user has full, uninterrupted access, even though multiple users are active. When many users are active simultaneously, system response time can increase, making delays more noticeable.
The multiprogramming os has a number of advantages. The following are some of them.
The multiprogramming os has a number of disadvantages. The following are some of them.
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The multiprogramming operating system refers to the ability to have multiple programs loaded into main memory and ready to execute, even on a single processor. When one program is waiting for an I/O operation, the CPU switches to another program, maximising CPU utilisation.
The operating systems (OS) are batch, multiprogramming, multitasking, network OS, real-time OS, time-sharing OS, and mobile operating systems.
The complete form of BIOS is the Basic Input Output System. BIOS is software built into a computer. This program is accommodated in read-only memory and is placed on the motherboard.
The GUI (graphical user interface) allows users to interact with the system through graphical elements and is normally user-friendly. CUI (Character user interface) relies on text-based commands and, while less intimate for beginners, offers speed and precision for experienced users.
The full form of OS is operating system. It is system software that manages computer hardware and software resources, providing standard services for computer programs.
The difference between RAM and ROM is that RAM which means Random Access Memory, is volatile, meaning it loses its data when power is cut off. It is used for the temporary storage of data that the computer is actively using, allowing for fast access. ROM Read-only memory) is non-volatile, meaning it retains its data even when power is off. It stores permanent instructions, such as firmware, needed for booting and operating the computer.
