Character strings separated by spaces are entered at the User Console and sent to the program USER by pressing Return. USER's command processor first attempts to identify the first string as a command name by comparing it with its internal dictionary of such names. If it is successful in making a match, one of two things may happen: (1) a command which does not take any arguments (e.g. GO) is executed immediately, or (2), if the command takes arguments (e.g. RA), the command interpreter will go on processing the input line until the requisite number of acceptable arguments have been analysed, after which the command is executed. If the input line is not exhausted the next character string is interpreted as a new command and processed in the same manner. Thus, commands can be staggered; delimiters are `space' and semicolon `;'. When the command processor is not able to match a character string with a command name, the program outputs a message and ignores the rest of the input line. Commands may have up to 7 qualifiers and 5 parameters. Most require a button on the Control Desk to be pushed for any action to occur, i.e. to `activate' the command. The full specification of an action can therefore be of the form: COMMAND/QUALIFIER1/QUALIFIER2/... PARAMETER1 PARAMETER2 ...
possibly followed by pressing a control panel button. Note that occasionally
parameters are associated with only one qualifier. Section 
gives a complete
list of commands, their qualifiers, parameters and any required control
panel interaction. The default qualifier for all commands which take
qualifiers is the first one given. If the user interface requires a parameter
which has not been specified it will request it with the prompt:
UI-Parm>
If you have changed your mind and don't want to give a value, just press Return and the command is ignored, i.e. the old value is retained.