UPX is a versatile executable packer with the following features:
* excellent compression ratio: typically compresses better than WinZip/zip/gzip, use UPX to decrease the size of your distribution !
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* very fast decompression: ~10 MB/sec on an ancient Pentium 133, ~200 MB/sec on an Athlon XP 2000+.
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* no memory overhead for your compressed executables because of in-place decompression.
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* safe: you can list, test and unpack your executables. Also, a checksum of both the compressed and uncompressed file is maintained internally.
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* universal: UPX can pack a number of executable formats.
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* portable: UPX is written in portable endian-neutral C++
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* extendable: because of the class layout it's very easy to add new executable formats or new compression algorithms
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* free: UPX is distributed with full source code under the GNU General Public License, and may be used freely even with commercial programs.
You probably understand now why we call UPX the "Ultimate Packer for eXecutables".
UPX is based on experience with our previous packers DJP and lzop and uses the NRV compression library.
Fuente : http://upx.sourceforge.net/
