Using Options ---> File Compression… from the menu bar, you can choose to store your HCM configuration in a compressed format. This choice is recommended, because compressed files consume less disk space and provide a better performance while opening and saving. Compressed work configuration files have a file extension of .hcmz while uncompressed ones have the traditional extension .hcm. Likewise, compressed production configuration files have a file extension of .hcrz while uncompressed ones have the extension .hcr.
If you compress an MCF-enabled configuration, the associated MCF is also compressed.
HCM can read and load both the uncompressed and the compressed formats. The file compression option is checked only when storing the files on the disk. The default format is uncompressed.