Compression is a method used to make files smaller in memory size to facilitate the electronic transfer of files to clients. The most common compression software used by and for MACs is the program, Stuffit. For PCs the most common program is called Zipit; MACs cannot create ZIP(.zip) files. Stuffit can create two basic compression files, SEA and SIT. These are nearly the same, but we send SIT files to the PC clients since some PCs are unable to open a SEA file. Practically all of the newspaper clients receive their weather package in compressed format. There is a program that will allow PC users to open SIT files, called Stuffit Expander for PC (see Stuffit Expander).