A solution for stocking information on your hard disk drive when the information becomes larger than its capacity is using archiving applications. Those programs have the role to compress information to enlarge the stocking capacity of your computer drives. Once compressed, the information loses its real signification on the system processor level. This is the reason why you first need to decompress a compressed file before you use it – to view its original information.
The archiving applications can be classified like this:
- compress files – ARJ, RAR, WINRAR, WINZIP;
- compress hard disk – STACKER.
The compress is done following the steps:
- search a sequence that repeats in the file;
- the sequence is replaced with a symbol (like a shortcut);
- after scanning the whole file or hard disk an index of the used symbols is added.
The text is: “He is tall. She is taller.”
Symbols for the repeated sequence: “#he &is $tall”
The index: “1# 2& 3$”
The compressed text: “# & $.S# & $er.”
This technique is very efficient for text files or databases. The space can be reduced to 70%. The executables can only be compressed 40%-50%.
· ARJ – has the best compression, but the compression time is
· PKZIP/PKUNZIP – offers the shortest time of compressing/decompressing; has great results when compressing long documents;
· LHA – is better compression than PKZIP, with a great time of archiving than ARJ;
· RAR – can unpack files compressed with ARJ or PKZIP.
The compressed files (the archives) can be transformed in executables; this is the situation when a compressing application is not necessary. In the real examples, this is included in the executable file and it is active once you launch it. This reduces the compressing rate because of this included sequence that needs approximately 15kb space.
You don’t need to know how to use this kind of programs. As a plus, there is the SHEZ application that has a universal menu for all the compression programs.
The disk compression programs, as a difference to the file compression applications have some particularities:
- they have superior speeds for compressing;
- they are transparent for the user;
- they eliminate the unused space remained unoccupied.
Those applications compress the space occupied on your hard disk with 50%-60%.
As you can see, this compression can be used on virtual drives created in the virtual memory (RAM drives), and that leads to a decreasing of the memory occupation degree and frees it for new application execution.
This application is included in MS-DOS package.
Dvrspace command launches the data compression program.
This program is similar to DoubleSpace – existing on the previous versions of this operating system. Anyway, it is using other data compression format; it has a user friendly interface (menus and helpful information).
Using drvspace command and some options you can do the same as in the DriveSpace menu, so you can run your program without opening the interface.
The DriveSpace usage is recommended when the existing space on the fixed drive is not sufficient. The data can be compressed to 50% space gain, but this is dependent to the file types on your disk.
If you have enough space the usage of this program it is not recommended, because its resident section occupies a 33kb RAM memory, so it can reduce the system performance.
The data compression is realized by indexing and not by a global referring of the initial file data. This way, the repeated sections of a file are only written once. But this depends on the file types, that’s why the text files can be better compressed that the bitmap files.
The system slow problem brought by the DriveSpace program is not available if your processor is a fast one or if you have enough Ram memory.
More, even if the system’s fixed drive has a poor transfer rate; DriveSpace can positively contribute to increasing speed performance of the system.