What Happens When Large Files Are Zipped?

Video Transcript

"HI, my name is Dave Andrews. Today I will talk to you about what happens when large files are zipped. Now when you take a file and you zip it up, basically you're running through a process called compression. And what that's doing is that's going to search your entire file for patterns that happen multiple times within the file. So instead of having those patterns appear multiple times within the file, they'll only going to save this large pattern once and then keep track of where it appears. That way you can take instead there being a whole bunch of copies of the same values over and over and over, you're basically getting a copy of the values once and then keeping track of where they appear in the document. So that greatly cuts down on your file size. I'm going to show you an example of this by going to our computer. I have a file here called myfile.txt. If I open it up, as you can see I have basically just taken asdf, the letters a, s, d and f and pasted them over and over and over again; so that, that's going to be the pattern basically that our compression scheme is going to be looking for. Let me close that. Now if I go to the properties of this file, you can see that it's 16 megabytes; that 16 megabytes of asdf appearing just over and over and over again. So I'm going to compress this by right clicking on it and going to send to and I'm going to click on compressed folder. Now that just created a zip file on my desktop called myfile.zip; if I go to the properties of this file, as you can see it's gone from being 16 megabytes now to 16.3 kilobytes which is a huge reduction in size. You can see that 16 million bytes there, almost 17 and then this one is just 16,000. So that's a huge amount of disc space that we've saved basically by pulling that pattern out and repeating it. My name is Dave Andrews and I've just talked to you about what happens when large files are zipped."