Compressed Files (ZIP, RAR, 7Z): What They Are and Why They Matter

 In the last post, we looked at file extensions. This time, let’s talk about compressed files-those that end with extensions like .zip, .rar, or .7z.

One of the first things we check when dealing with files is their size. File size represents how much space the file takes up on a storage device, measured in bytes (B). The units scale upward from KB (kilobyte), MB (megabyte), GB (gigabyte), to TB (terabyte). For example, a simple Notepad document may only be a few KB, while a photo is usually several MB, a music file can be tens of MB, and a movie might reach several GB. In Windows, you can right-click a file and select Properties to see its exact size.


photo by cottonbro studio on pixels


But as files grow larger, or when there are too many of them, things get inconvenient. Imagine attaching 100 photos to an email, or needing to send an entire project folder to someone. Sending each file individually is inefficient, and large files take a long time to transfer. This is where compressed files come in. Compression bundles multiple files into one while reducing their size-similar to putting bulky winter clothes into a vacuum-sealed bag to shrink them down. Smaller files save storage space and make transfers much easier.


7-Zip program


Compression isn’t just about convenience-it has been historically significant. In the 1980s and 1990s, storage was very limited, with floppy disks and small hard drives. Compression software like PKZIP became essential to fit more data into limited space and to speed up transfers over slow phone-line internet connections. Even though today’s devices have far more storage and faster internet, compression remains indispensable for efficient file transfer and organization.

Another major benefit of compression is organization. Instead of sending dozens of scattered files (documents, images, videos), you can compress them into a single file. The recipient simply extracts it and instantly gets the entire set neatly restored. This makes compression just as useful for sharing as it is for saving space.


WinRAR program


To use compressed files, you need to extract (decompress) them first. The compressed data is restored to its original state through special algorithms, and importantly, the extracted files are identical to the originals. This ensures that data can be shared safely without quality loss.


ALZip program

Today, there are many compression tools available. Windows has built-in ZIP support, so you can compress and extract basic files without installing extra software. But for more advanced features or higher compression rates, dedicated programs are used, such as 7-Zip, WinRAR, and ALZip.

  • 7-Zip is free and powerful, widely used around the world.

  • WinRAR offers high compression rates and split archive functionality, making it popular for large file management.

  • In Korea, ALZip has been popular for years, even introducing its own .alz format.

Different compression file extensions exist, each with their own strengths:

  • .zip: the most common and highly compatible (works on both Windows and macOS).

  • .rar: known for strong compression and advanced features.

  • .7z: open-source, efficient, and flexible.

  • .tar.gz: widely used in Linux, which first bundles files with TAR and then compresses them with Gzip.

Extensions tell you which program you need to open the file, so it’s always important to check them.

In summary, compressed files are tools that make storing, organizing, and sharing data easier by reducing size and bundling multiple files into one. From the days of limited storage to today’s high-capacity systems, compression has always been a core technology in computing. By understanding common formats like ZIP, RAR, and 7Z, even beginners can handle files more efficiently.

That’s it for today’s post on compressed files.
Next time, we’ll explore drives (storage devices) and how files are stored on them.

Thank you for reading, and as always, I wish you happiness!


You can view the original Korean blog post at the link below

View in Korean


Location: 대한민국 서울특별시

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