what happens when files that contain large amounts of information are zipped?

Answer 1

The become files that contain large amounts of compressed data. ;0

Think of hte compression as searching for repeated characters and reducing those down to just a character and a number. (Not actually accurate, but gives an idea.)

Answer 2

Data compression is a highly advanced topic in computer science and mathematics. ZIP does it's magic with a combination of two techniques: Huffman coding and the LZ77 algorithm.

The simple explaination is:
Imagine you had a file with the following text: "RRRREEEDDDDDDD". Compressing it might be turning the file into "R4E3D7". While it's pretty unlikely that you'd have a bunch of repeating letters, there's a good chance that you'll have a lot of repeating colors next to each other in a digital picture. ZIP files and GIF/PNG image files all use similar forms of data compression.

(JPEG pictures and MP3s are also compressed, but they work a bit differently by actually discarding some of the data to make the whole thing smaller. Hence, they're compressed using "lossy" compression. It's why some JPEGs look a little blocky and why CDs sound a little more lively than MP3s.)

Answer 3

A map is made of all similarly marked bytes in the file that contains a compression algorythm.

Basic example.

A text file has the following numbers 1110000000
The zip program would see three ones and five zeros.
It could then convert the file into 3150.
Now there is six less memory spaces required to hold that 4 digit number than the 10 digit number above it.
The software that decompresses all ready knows that the three is a key and the 1 is it's value - and the five is a key with 0 as it's value. so when decompressing it goes okay I need to make three ones and five zeros, hence: 11100000!

This is a gross simplification but all data is comprised of 1's and 0's so it illustrates the point.

Answer 4

then if you want to open them you have to undress them