Know How the Process Control Block Works

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Think about the complexities associated with computing – even in its most basic forms.

How does a program, say a chat platform for example, know how to handle all its associated tasks in the right order? Sending and receiving data, verifying the source, encoding, and doing it all with the right amount of resource use in minimal downtime – how does it all work?

While there are many factors at play, it is important to remember that systems are already programmed to handle these common tasks according to a set hierarchy of operations. This not only helps keep the systems reliable, but fast as well.

When it comes to technology and especially open-source computing systems, scheduling tasks is extremely important. While process scheduling is important with any OS, open-source systems rely on their own distinct data structure for handling these responsibilities.

While many people may be familiar with task scheduling and process management in standard proprietary operating systems like Windows or Mac OS, process control block (PCB) is particularly prominent with systems like Linux. But what exactly is this process, and why is it important?

Process control block goes by many names, and it has a massive level of importance on how a system runs, how responsive it is (or isn’t) and how many standard operations a system can carry out.

PCB: A Data Structure With Many Names

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PCB goes by many different names. It’s sometimes called task controlling block, entry of the process table, Switchframe, and even task struct.

No matter what a person calls it, the end result is the same – it’s a data structure that functions within the operating system’s kernel and provides an important function among core files. It contains the information and commands needed to manage process scheduling, and manage everything from standard computing to user-inputted commands.

PCB is sometimes called the manifestation of a process in an operating system – the electrical circuits that move through the motherboard to carry out commands, the results of those commands, and all the coding that helps prop up the process – all of this is a product of PCB.

Process control blocks can also be referred to as a process control system (PCS) and the data structure is used in many situations. From casual computing operations to largescale industrial tasks, there are many situations where users can observe the importance of the process control block.

Before we move forward explaining the intricacies of the process control block, let’s examine some of the common terms used when discussing this data structure.

1. Process

The term process can sometimes be a bit confusing when used in computing conversations. Technically, everything from a CPU fan spinning to an OS asking for a password represents a type of process in some sense of the word. But the correct interpretation of the term in this context involves any instance of a program in execution.

A process can exist in five states – new, ready, running, waiting, and terminated. For the sake of the process control block, we’ll be dealing with processes that are ready (receiving instructions), running (processing instructions), or waiting (paused until proper specs are available to carry out commands).


The term “block” in process control block refers to a stored unit of information concerning process-specific ordering of tasks. This could involve everything from a command to verify the publisher of a program for security purposes to scheduling execution to management memory allocation as the task goes on.

Blocks, like processes, are sometimes referred to by a variety of terms in the tech community. But in the context of this situation, they refer to collections of information and commands that exist with every process on a system.

3.Process Scheduling

Scheduling is a topic discussed constantly when the topic of the process control block comes up. This is because each block’s schedule of tasks and commands is aimed at one overall end – to use the computer’s CPU and other resources to effectively carry out commands.

This involves minimizing response time through efficient resource allocation. But, along with making sure the computer’s components are used efficiently, this also involves making sure the commands in a schedule are processed in an orderly and timely fashion.

Here’s how the process control block works, starting with how the structure of a block begins. Each block’s structure is system-dependent. This means it can be influenced by everything from the version of the OS being used to the type of hardware the system is working with. However, every process control block operates off three primary categories.

These categories include process identification data, process state data, and process control data. Status tables are created for data in each entry, allowing for the efficient management of multiple process. The system of virtual tables reveals how the control block operates – each task has a specific place in the hierarchy, and it must be completed before the next one can be started.

This is important for making sure things move in order so compatibility issues are avoided. It’s also important for safety purposes. For example, if a process’s source can’t be identified, the system will likely not run it without administrator permission to avoid potential security holes. Likewise, a process must have memory and CPU resources allocated beforehand to ensure it doesn’t overburden the system and lead to hardware problems.

Each block typically contains an ID number, pointers for relevant program locations, registry data, information about permission flags, memory requirements, file lists, status of required devices, and of course the priority of the process.

Sometimes a process control block may skip through certain steps of the table, though there is a reason for this – it moves to logical spots based off the requirements of the task at hand and how the system can handle each command within the block.

The process control block can be thought of as a checklist, or even a miniature to-do list for each process on a computer. Usually, a person can manage multiple processes on their system without issue. But the only time trouble can really arise is when multiple high-resource processes are running at the same time on a system not built to handle such tasks.

What If The System Can’t Carry Out The Tasks?

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Let’s say you’re trying to complete a process on your system that you know you have the hardware specs for. But you find that you’re not getting the exact result you want – is something stuck in the process control block, and how can you check?

The main purpose behind a process control block is to carry out tasks with minimal wait-time. If there is a delay, it could be a sign of a standard computer issue that even a simple restart could fix. But if the problem persists, it could be a sign of a more serious issue like a driver problem or even a lack of hardware setup.

Consider how systems with dual-CPU setups will split tasks between them for better balance and better response times. If you’re familiar with going into the command line, you can actually discover which aspects of a process control block are causing you problems that way. If you still have trouble despite all common trouble areas being addressed, it could be wise to make sure your OS has all critical files installed as this could be a potential problem source as well.

But in most cases, it’s likely that a person will find the process control block carries out most basic tasks with little trouble at all. But just knowing how the process scheduling structure works provides insight into how a system works and how the most basic of tasks are carried out through complex and strategically ordered command tables.

How PCB Compares To Other Task Scheduling Processes

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Every operating system and every type of digital device relies on some type of process scheduling structure. Even a simple piece of hardware like a wearable fitness device must keep track of at least a few basic tasks and carry them out in the right order. As you would imagine, things get more complex when you move to bigger systems with more demands.

Even a system like Windows that automates much of the task scheduling process and never requires a user to open command line or command prompt use data structures similar to PCB. While these data structures are primarily tailored to open-source systems, they’re a great example of how prioritization and resource allocation matter so much with technology.

How does a processor know how much power to put toward a task? How do systems stop themselves from doing tasks out of order and causing problems? How can multiple tasks be carried out in quick succession to minimize downtime? The answer to all these is simple – good task scheduling protocols.

The process control block is a system used for effectively sorting task components, assigning them an ID for easy organization, and keeping things processing in the right order.

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