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What are zip files and why are they used to extract original data from compressed files



Zipped (compressed) files take up less storage space and can be transferred to other computers more quickly than uncompressed files. In Windows, you work with zipped files and folders in the same way that you work with uncompressed files and folders. Combine several files into a single zipped folder to more easily share a group of files.


If you add encrypted files to a zipped folder, they'll be unencrypted when they're unzipped, which might result in unintentional disclosure of personal or sensitive information. For that reason, we recommend that you avoid zipping encrypted files.




what are zip files and why are they used




Some types of files, like JPEG images, are already highly compressed. If you zip several JPEG pictures into a folder, the total size of the folder will be about the same as the original collection of pictures.


Zip files can be used for a lot different things. File compression, encryption, split archives, and more are all just a few clicks away once you understand the different things that zip archives are capable of.


As you can see in the screenshot, the files are copied into the zip folder, and not moved or deleted from their original location. Now, you can transfer, backup, or do whatever else you want with your zipped contents.


A new window will open up and you can select where you want the files to be extracted. By default, it will extract the contents to the same directory in which your zip file resides. Just hit extract and a folder will be created that has all of the zipped files in it.


7-Zip is a free file archiver for Windows that comes with all the options that you should ever need for zip files. Click that link to be taken to their website and download the latest version of the program. Installation is straightforward, just accept the license agreement and click next until 7-Zip is installed.


File compression is an important part of the digital workspace. ZIP files use compression to send more data at faster speeds than has ever been possible. This is why ZIP files are such a popular tool for businesses all across the world. But what exactly is a ZIP file?


ZIP files work in much the same way as a standard folder on your computer. They contain data and files together in one place. But with zipped files, the contents are compressed, which reduces the amount of data used by your computer. Another way to describe ZIP files is as an archive. The archive contains all the compressed files in one location. So, the ZIP file format is one option to use if you need to make a single file or group of files smaller.


There are a broad range of potential uses for zipped files in a business setting. Being able to send large numbers of files over email is imperative. Say you need to send a big batch of files to a colleague or client. If you try to send them all at once in an email attachment, you will get an error message because of file size. So you could try to send each file as in separate emails. But this is time consuming, labor intensive, and could lead to duplicate files. To send all the files in one email, you can zip them and attach this single ZIP file to your email. Your recipient can then unzip the file by downloading and clicking.


One of many disadvantages associated with ZIP archive files is compression limits. Some files cannot be compressed much more than they already are. This is especially true for MP3 files and JPG files. So, if you frequently work with video and image files, the ZIP format won't help you save very much storage space.


ZIP files are also difficult to use if you are on the go. If you're using a phone or tablet, you would need to use a file saved on your phone and a third-party app. This would create problems both with file storage space as well as security.


When you compress a folder to zip, it works by applying certain compression algorithms to the files within the folder. The most common is the "DEFLATE" algorithm, a combination of LZ77 and Huffman codes.


To put it simply, LZ77 will look for sequences of data in your files that reoccur, which often is a lot. The algorithm then uses pointers to point back to where the reoccurring data has been seen before in your files.


If you want to keep files within folders but use the files sparingly, a great way to is to compress them. This method keeps them both organized and more lightweight, saving you space on your hard drive. And when you want to use the files, extract them from your compressed file.


ZIP is an archive file format that supports lossless data compression. A ZIP file may contain one or more files or directories that may have been compressed. The ZIP file format permits a number of compression algorithms, though DEFLATE is the most common. This format was originally created in 1989 and was first implemented in PKWARE, Inc.'s PKZIP utility,[2] as a replacement for the previous ARC compression format by Thom Henderson. The ZIP format was then quickly supported by many software utilities other than PKZIP. Microsoft has included built-in ZIP support (under the name "compressed folders") in versions of Microsoft Windows since 1998 via the "Plus! 98" addon for Windows 98. Native support was added as of the year 2000 in Windows ME. Apple has included built-in ZIP support in Mac OS X 10.3 (via BOMArchiveHelper, now Archive Utility) and later. Most free operating systems have built in support for ZIP in similar manners to Windows and Mac OS X.


ZIP files generally use the file extensions .mw-parser-output .monospacedfont-family:monospace,monospace.zip or .ZIP and the MIME media type application/zip.[1] ZIP is used as a base file format by many programs, usually under a different name. When navigating a file system via a user interface, graphical icons representing ZIP files often appear as a document or other object prominently featuring a zipper.


WinZip, starting with version 12.1, uses the extension .zipx for ZIP files that use compression methods newer than DEFLATE; specifically, methods BZip, LZMA, PPMd, Jpeg and Wavpack. The last 2 are applied to appropriate file types when "Best method" compression is selected.[28][29]


.ZIP files are archives that store multiple files. ZIP allows contained files to be compressed using many different methods, as well as simply storing a file without compressing it. Each file is stored separately, allowing different files in the same archive to be compressed using different methods. Because the files in a ZIP archive are compressed individually, it is possible to extract them, or add new ones, without applying compression or decompression to the entire archive. This contrasts with the format of compressed tar files, for which such random-access processing is not easily possible.


A directory is placed at the end of a ZIP file. This identifies what files are in the ZIP and identifies where in the ZIP that file is located. This allows ZIP readers to load the list of files without reading the entire ZIP archive. ZIP archives can also include extra data that is not related to the ZIP archive. This allows for a ZIP archive to be made into a self-extracting archive (application that decompresses its contained data), by prepending the program code to a ZIP archive and marking the file as executable. Storing the catalog at the end also makes possible hiding a zipped file by appending it to an innocuous file, such as a GIF image file.


A ZIP file is correctly identified by the presence of an end of central directory record which is located at the end of the archive structure in order to allow the easy appending of new files. If the end of central directory record indicates a non-empty archive, the name of each file or directory within the archive should be specified in a central directory entry, along with other metadata about the entry, and an offset into the ZIP file, pointing to the actual entry data. This allows a file listing of the archive to be performed relatively quickly, as the entire archive does not have to be read to see the list of files. The entries within the ZIP file also include this information, for redundancy, in a local file header. Because ZIP files may be appended to, only files specified in the central directory at the end of the file are valid. Scanning a ZIP file for local file headers is invalid (except in the case of corrupted archives), as the central directory may declare that some files have been deleted and other files have been updated.


For example, we may start with a ZIP file that contains files A, B and C. File B is then deleted and C updated. This may be achieved by just appending a new file C to the end of the original ZIP file and adding a new central directory that only lists file A and the new file C. When ZIP was first designed, transferring files by floppy disk was common, yet writing to disks was very time-consuming. If you had a large zip file, possibly spanning multiple disks, and only needed to update a few files, rather than reading and re-writing all the files, it would be substantially faster to just read the old central directory, append the new files then append an updated central directory.


Each entry stored in a ZIP archive is introduced by a local file header with information about the file such as the comment, file size and file name, followed by optional "extra" data fields, and then the possibly compressed, possibly encrypted file data. The "Extra" data fields are the key to the extensibility of the ZIP format. "Extra" fields are exploited to support the ZIP64 format, WinZip-compatible AES encryption, file attributes, and higher-resolution NTFS or Unix file timestamps. Other extensions are possible via the "Extra" field. ZIP tools are required by the specification to ignore Extra fields they do not recognize.


The .ZIP specification also supports spreading archives across multiple file-system files. Originally intended for storage of large ZIP files across multiple floppy disks, this feature is now used for sending ZIP archives in parts over email, or over other transports or removable media. 2ff7e9595c


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