UPX achieves an excellent compression ratio and offers very fast decompression. Your executables suffer no memory overhead or other drawbacks for most of the formats supported, because of in-place decompression.
Main features:
-excellent compression ratio: typically compresses better than WinZip/zip/gzip, use UPX to decrease the size of your distribution!
-very fast decompression: ~10 MB/sec on an ancient Pentium 133, ~200 MB/sec on an Athlon XP 2000 .
-no memory overhead for your compressed executables because of in-place decompression.
-safe: you can list, test and unpack your executables. Also, a checksum of both the compressed and uncompressed file is maintained internally.
-universal: UPX can pack a number of executable formats.
-portable: UPX is written in portable endian-neutral C .
-extendable: because of the class layout it's very easy to add new executable formats or new compression algorithms.
-free: UPX is distributed with full source code under the GNU General
