Smart way of Compressing Files

Devakinandan
4 min readJan 28, 2024

How ZIP Files work?

How ZIP File Works: A Simple Explanation

ZIP is a popular file format that allows you to compress one or more files into a single archive, reducing the file size and making it easier to store or share. But how does ZIP file work? In this blog post, we will explain the basic principles of ZIP file compression and decompression, and how you can use ZIP files in your daily work.

What is ZIP File?

ZIP file is a type of archive file format that uses lossless data compression, meaning that no data is lost when compressing or decompressing the file. ZIP file can contain any type of file, such as documents, images, videos, audio, etc. You can also create ZIP files that contain multiple files or folders, which are called ZIP archives.

The main advantage of ZIP file is that it reduces the file size by removing redundant or unnecessary data from the file. This can save storage space and bandwidth, and speed up the file transfer or download. For example, a 10 MB file can be compressed to 5 MB or less using ZIP file compression.

The main disadvantage of ZIP file is that it requires extra time and processing power to compress and decompress the file. This can affect the performance of your computer or device, especially if you are dealing with large or complex files. Also, some files may not be suitable for ZIP file compression, such as already compressed files (e.g., JPEG, MP3, etc.) or encrypted files.

How Does ZIP File Compression Work?

ZIP file compression works by encoding the information in the file into fewer bits, using various compression algorithms. The most common compression algorithm used by ZIP file is DEFLATE, which combines two techniques: Huffman coding and LZ77.

Huffman coding is a method of assigning variable-length codes to the symbols (e.g., characters, bytes, etc.) in the file, based on their frequency of occurrence. The more frequent a symbol is, the shorter the code assigned to it. For example, in a text file, the letter “e” may appear more often than the letter “z”, so the code for “e” may be “01” while the code for “z” may be “11011”. This way, the file size can be reduced by replacing the symbols with their codes.

LZ77 is a method of finding and eliminating repeated sequences of symbols in the file, by replacing them with references to their previous occurrences. For example, in a text file, the phrase “the best” may appear multiple times, so instead of writing it every time, it can be replaced with a pointer to the first occurrence, such as “(12,8)”, which means “go back 12 symbols and copy 8 symbols”. This way, the file size can be reduced by avoiding duplication.

By combining these two techniques, ZIP file compression can achieve a high compression ratio, depending on the type and content of the file.

How Does ZIP File Decompression Work?

ZIP file decompression works by reversing the compression process, using the same compression algorithm and parameters. The compressed file is read bit by bit, and the codes are decoded into the original symbols, using the Huffman coding table. Then, the references are replaced with the corresponding sequences of symbols, using the LZ77 sliding window. This way, the original file is restored from the compressed file.

How to Use ZIP File?

To use ZIP file, you need a software application that can create and extract ZIP files, such as WinZip, 7-Zip, or the built-in ZIP support in Windows or macOS.

To create a ZIP file, you need to select the file or files that you want to compress and choose the option to add them to a ZIP archive. You can also adjust the compression level and other settings, such as encryption, password protection, split size, etc. The ZIP file will be created in the same location as the original files, or in a location of your choice.

To extract a ZIP file, you need to open the ZIP file and choose the option to extract the files to a folder. You can also view the contents of the ZIP file without extracting them and select the files that you want to extract. The extracted files will be placed in the same folder as the ZIP file, or in a folder of your choice.

Conclusion

ZIP file is a useful file format that can help you compress and decompress files, saving space and time. ZIP file works by encoding the information in the file into fewer bits, using compression algorithms such as DEFLATE. To use ZIP file, you need a software application that can create and extract ZIP files, or an online tool or cloud service that can handle ZIP files. We hope this blog post has helped you understand how ZIP file works, and how you can use it in your daily work.

--

--

Devakinandan

"I like to give more value to my readers than I receive""