Ever since the computer age began, boffins have worked to reduce the amount of space required by digital data through compression. Take music, for instance. A typical album in CD format uses about 600MB of storage. Converted to MP3s, however, the files are compressed to just 60MB.
MP3 files, Jpegs and Mpeg2 videos all use ‘lossy’ compression. This reduces file sizes by stripping out data deemed inessential – frequencies beyond the range of human hearing, for example, and sounds masked by other noise. Data is irretrievably lost but, unless the compression is overly aggressive, an MP3 version of a track should be perceptually near-identical to the original.
For data such as text, however, lossy compression is useless. Can you imagine what would happen if you stripped all the spaces out of a Word document? What’s required here is ‘lossless’ compression.
Lossless compression is what the ubiquitous Zip format is all about. Files are reduced in size, but everything is left intact. To decompress a batch of files, simply extract it.
Zip files (also known as archives) have numerous uses, but are perfect for emailing documents and images. Uploading and downloading email attachments can take an age, but compression lessens the burden. Indeed, without compression, some attachments might be too big to email at all. We’ll be focusing on compressing files for use as email attachments over the following pages.
Windows comes with built-in Zip support, but this is limited to basic creation and extraction. To unleash the format’s full power and flexibility you’ll need to use a third-party utility.
The big hitters here are WinZip and WinRAR but, while both are great, neither is free. Once the trials expire, you’re expected to dig into your pocket.
Throughout this workshop, we’ll be using 7-Zip. This has all the features of its rivals and costs a grand total of zip.
1. Grab the version of 7-Zip most suitable for your operating system. Installation is straightforward – a simple matter of accepting the defaults although, depending on your PC’s setup, you might be prompted to reboot.
2. Right-click the file you want to compress and select 7-Zip. To compress the file immediately and save the archive to a current folder, simply click ‘Add to “xxx.zip”’ (where xxx is the file name). To tap into 7-Zip’s full range of features and settings, select ‘Add to archive’.