Start with the title of the software, in this case, "Illustrator."
Add the version, such as "5.5" -- write down whatever version you are using.
Add the city of publication, year of publication and form the software was packaged in, such as "downloaded," "DVD" or "floppy disk."
Punctuate the citation with periods after the major elements. All publication information is joined with a colon and comma. A finished citation for CS5 looks like this: "Adobe Illustrator. Vers. CS5. San Jose, California: Adobe Systems, Inc., 2010. Computer software." Omit the quotation marks.