What is a file?

if you are a visual learner and want some practical learning here is the video

Simple question, what is a computer file? eg. image,pdf,docs etc.

When you think of a file on your computer, you probably imagine documents, pictures, videos, or maybe some code files. But what is a file really? At its core, a file is just a collection of tiny pieces of data called bytes stored on your hard drive or SSD. These bytes are made up of zeros and ones, and it’s the way these bytes are put together and read that makes one file a photo and another a song or a text document.

If every file is a sequence of bytes, how do they differ?

It all depends on how a program reads those bytes. For example, a text editor sees the bytes as letters and words. An image viewer sees those same bytes as pixels that come together to form a picture. This “reading” is called encoding, and different file types have different rules for how bytes turn into something meaningful.

The Magic Numbers

Here’s a cool trick your computer uses to know what kind of file it’s dealing with a file’s "magic number." It’s a special set of bytes right at the very start of every file, kind of like a fingerprint. This helps your computer instantly recognize if a file is a PDF, a PNG image, or something else, no matter what the file is named.

So, renaming a file from “mypic.png” to “mypic.pdf” doesn’t actually change the file. Inside, it’s still an image, and programs will get confused if you try to open it like a PDF.

Find out more here https://en.wikipedia.org/wiki/List_of_file_signatures

Why Do File Extensions Matter Then?

File extensions, the .txt, .jpg, .pdf parts are like labels that help your operating system decide which app should open the file. They don’t actually change the file’s content, but they guide your computer on where to send the file when you double-click it.

What Happens If You Open a File the Wrong Way?

If you try to open a picture file with a text editor, you’ll see a bunch of weird, jumbled characters. That’s because the text editor is trying to read image data as if it were text. On the other hand, your image viewer knows exactly how to make sense of those bytes and shows you the photo beautifully.

In simple terms, a computer file is just a string of bytes, and the magic lies in how computers and programs read and understand those bytes. The combination of magic numbers and file extensions helps your computer know exactly what to do with each file.

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