About 7-Zip Format¶
Description¶
For further information, please visit https://www.7-zip.org
7z is an archive format, providing high compression ratio, by Igor Pavlov. Main features of the 7z format:
-
Open architecture
-
High compression ratio
-
Strong AES-256 encryption
-
Ability to use any compression, conversion or encryption method
-
Supporting files with sizes up to 16000000000 GB
-
Unicode file names
-
Solid compressing
-
Archive headers compressing
7z has open architecture, so it can support any new compression methods.
The following methods are integrated into 7z:
| Method | Description |
|---|---|
| LZMA | Improved and optimized version of LZ77 algorithm |
| LZMA2 | LZMA-based compression method. It provides better multithreading support than LZMA. |
| PPMD | Dmitry Shkarin's PPMdH with small changes |
| BCJ | Converter for 32-bit x86 executables |
| BCJ2 | Converter for 32-bit x86 executables |
| BZip2 | Standard BWT algorithm |
| Deflate | Standard LZ77-based algorithm |
LZMA is the default and general compression method of 7z format. Main features of LZMA method:
-
High compression ratio
-
Variable dictionary size (up to 4 GB)
-
Compressing speed: about 1 MB/s on 2 GHz CPU
-
Decompressing speed: about 10-20 MB/s on 2 GHz CPU
-
Small memory requirements for decompressing (depend from dictionary size)
-
Small code size for decompressing: about 5 KB
-
Supporting multi-threading and P4's hyper-threading
LZMA compression algorithm is very suitable for embedded applications. If you want to use LZMA code, you can ask for consultations, custom code programming, and required developer licenses at 7-zip.org.
External links for developers:
Technical Notes¶
7-Zip compression system of Paquet Builder is based on 7-Zip and LZMA SDK 19.0.
7-Zip Self-Extractors made with Paquet Builder do not support BZip2 nor Deflate methods because LZMA2, LZMA, BCJ/BCJ2 and PPMD are enough to achieve good compression ratios.