I saw article tile ——"Compress and uncompress files (zip files)" from Windows 7 document here.
What's the difference between "zip" and "compress" and “pack”? Is it the same thing? I am so confused and need your help.
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PK-Zip is one particular program that compresses files in the 'zip' format. Support for zip files is built into Windows, so many people conflate compression with zip files.
With no specific reference to the article that you cited I will tell you that
pack are three commands used in different operative systems to compress and package files in different ways (see below for further details). In Unix you can find all even if not any more so used.
- (Computer Science) computing (tr) to compress (a file) in order to reduce the amount of memory required to store it or to make sending it electronically quicker.
From the free dictionary site 
It happens often that when a new technology spread in the common life, jargon (slang) terms became of common use even when they came from a different language .
Note that term
zip can even be referred to the extension of a compressed file (e.g.
MyFile.zip) as well as the specific algorithm used to compress the files.
Referring to the article you cited, over there it is reported
Compressed (zipped) folder in a proper way, because the algorithm used in this case is the zip one.
When a programmer creates a tool that do something it is not uncommon that he tries to choose a name that will remember the action easier. So they firstly used
compress... When that name is yet used they invent other as
arj (that means Archived by Robert Jung),
The confusion arises because with the same term you have a specific program and an action performed from that command: ideed in Unix it exists a command
find to find the files. This confusion can be increased some times after if the command becomes obsolete but not the term chosen for it...
The further details, or at least some of them
The zip program puts one or more compressed files into a single zip archive, along with information about the files... has one compression method (deflation) and can also store files without compression...
Deflation uses a combination of the LZ77 algorithm and Huffman coding
The compress utility reduces the size of files using adaptive Lempel-Ziv coding. Each file is renamed to the same name plus the extension .Z
pack compresses files using a Huffman minimal redundancy code on a byte basis. Each file is compressed in place; the resulting file has a .z extension appended to the file name, but keeps the same owner and permissions. The times of last access and last modification are also preserved.