After the program name as , the command line may contain options and file names. Options may appear in any order, and may be before, after, or between file names. The order of file names is significant. Each option changes the behavior of as . No option changes the way another option works.
All options are optional.
Some options expect exactly one file name to follow them. We use the phrase source program , abbreviated source , to describe the program input to one run of as . The source program is a concatenation of the text in all the files, in the order specified. Each time you run as it assembles exactly one source program. The source program is made up of one or more files.