XSPEC is a command-driven, interactive program. The user will see a prompt whenever input is required. If the user is uncertain about how to respond to a particular prompt, typing ¸? usually will produce a list of valid responses.
XSPEC is designed to allow complicated, multi-instrument analysis, so most commands can take arguments specifying more than one data set. Arguments in XSPEC may be separated by either blanks or commas.
A single argument can define a range. The ranges are delimited by two dashes (-). A colon (:) is used to separate ranges (e.g., the phrase 1-2:11-24 refers to channels 11 - 24 in files 1 and 2).
Operating-system commands can be given from within XSPEC by prefixing the command with dollar sign ($ ). A set of XSPEC commands in a file can be input using @filename. This command file can take arguments. Note that all commands, with the exception of fakeit, can be abbreviated to unique strings. Command recall and inline editing are available and configurable by the user. The alias command enables a user to define his or her own command in terms of other XSPEC commands.