UPX description
UPX - The BEST free, portable, extendable, high-performance executable packer

UPX is a portable, free, extendable, high-performance executable packer for several different executable formats.

It achieves an excellent compression ratio and offers very fast decompression. Your executables suffer no memory overhead or other drawbacks.

UPX supports a number of different executable formats, including
Windows 95/98/ME/NT/2000/XP programs and DLLs, DOS programs,
and Linux executables.

Here

are some key features of "UPX":

· 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