7-zip is a popular compression tool and famous for high compression ratio. But unfortunately, there is no description in the man pages about switching the compression algorithm to PPMd . Actually, PPMd provides very high compression ratio with lower CPU power consumption with a text data, and I would like to show its efficiency. Here is an example. Below is a comparison of size and CPU time between variety of compression methods . command size time 7z a -tzip -mx=9 3699 bytes 0m0.410s 7z a -tgzip -mx=9 3610 bytes 0m0.411s 7z a -tbzip2 -mx=9 3363 bytes 0m0.608s 7z a -m0=lzma -mx=9 3406 bytes 0m0.109s 7z a -m0=PPMd -mx=9 2699 bytes 0m0.058s The original file is a 6795 byte text file. As you can see, efficiency of PPMd is outstanding! PPMd helps me a lot to...