Concurrency (computer science) facts for kids

In concurrent computing, a computer seems to do many things at the same time. Imagine you are a chef cooking a meal. You might chop vegetables, stir a pot, and preheat the oven all in the same general time, switching between tasks quickly. This is similar to how a computer handles concurrent tasks.

It means that different parts of a computer program can make progress on their jobs without waiting for each other to finish completely. This way of organizing computer programs helps them work more efficiently.

What is Concurrency?

Concurrency is a way of designing computer programs so they can handle many tasks at once. Even if a computer only has one main brain, called a processor, it can quickly switch between different tasks. This makes it seem like all tasks are running at the same time.

How Computers Multitask

Think of a computer's processor as a very fast juggler. It can only hold one ball (task) at a time, but it switches between them so quickly that all the balls stay in the air. Each "ball" can be a small part of a program, called a thread or a process.

• A process is like a whole separate program running, such as your web browser or a game.
• A thread is a smaller part of a process. A single program can have many threads working on different parts of the same job.

When these threads or processes work asynchronously, it means they don't have to wait for each other. They can progress at their own speed.

Concurrency vs. Parallel Computing

It's easy to confuse concurrency with parallel computing, but they are different.

• Concurrency is about managing many tasks that appear to run at the same time, even on a single processor. It's about handling multiple tasks over overlapping time periods.
• Parallel computing is when a computer truly does many things at the exact same moment. This happens when a computer has multiple processors or "brains." Each processor can work on a different task at the same time.

So, concurrency is about dealing with many things at once, while parallelism is about doing many things at once.

Why is Concurrency Important?

Concurrency is very important for modern computers and apps.

• Responsiveness: It allows apps to stay responsive. For example, you can type in a document while your word processor saves it in the background.
• Efficiency: It helps computers use their resources better, especially when waiting for things like data from the internet or a hard drive. While one part of a program waits, another part can keep working.
• Complex Tasks: Many complex tasks, like running a video game or a web server, need to handle many actions at once. Concurrency makes this possible.

Challenges with Concurrency

While useful, concurrency can also create challenges for programmers. When multiple tasks try to use the same resource (like a piece of data or a file) at the same time, it can lead to problems.

• Race Conditions: This happens when the outcome of a program depends on the exact order that tasks finish. If one task changes data before another task reads it, it can cause errors.
• Deadlocks: This is like a traffic jam where two cars are waiting for each other to move, so neither can proceed. In computing, two processes might be waiting for a resource that the other process holds, causing both to stop.

Computer scientists like Edsger W. Dijkstra have studied these problems to find ways to make concurrent programs work smoothly and correctly.

Images for kids

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  The "Dining Philosophers", a classic problem involving concurrency and shared resources