After start--up, the MIDAS monitor prompts you to interact with MIDAS
by entering commands on the terminal terminated by 
(Enter key).
To enter a command-line on more than one terminal/window line, use
the continuation character, a minus sign ( -), as the last character of a
line. The command line is limited to 256 characters.
If you want to enter more than one command on a single line, separate the
commands with a semicolon and space ( ; ).
A MIDAS command line is structured as
command/qualifier par1 par2 ... par8 !comments
The command describes the general action you want to perform (a verb) and
the qualifier usually specifies the object of that action, e.g.
WRITE/DESCRIPTOR.
The command parameters (max. 8) hold all other information needed to
perform the
required action. All parameters are separated by spaces.
Currently the following ``objects'' exist in MIDAS:
All user input and output from MIDAS commands is recorded in an ASCII
file, named FORGRxy.LOG (with xy the MIDAS unit) and stored in the
MID_WORK directory. This MIDAS logfile
serves as a hardcopy of a full MIDAS session. Terminating MIDAS with BYE
and continuing later on via gomidas will not restart a new logfile
but append to the existing one.
The logging in MIDAS
can be
controlled via commands like LOG/OFF, LOG/ON, LOG/TOF, DELETE/LOG.
Comments may be appended to the command string and are separated by at
least one white space and `!' (exclamation mark) from it.
To give a complete line of comments, enter `!' as the first character
of the input line (useful for structuring the contents of
the MIDAS logfile).
Commands and qualifiers may be abbreviated to the number of significant characters needed to distinguish them from the rest. At most 6 characters are necessary for the command and 4 characters for the qualifier. Command and qualifier are separated by a `/' (slash). Nearly all commands need a qualifier, but there is only one qualifier per command (e.g. comm/qual1/qual2 is unsupported in MIDAS). In case you omit the qualifier, the default qualifier of that command is used by MIDAS. The default qualifier of a MIDAS command may be displayed via SHOW/COMMAND command. For example, the default qualifier for the LOAD command is IMAGE, so typing LOAD/IMAGE or LOAD will have the same effect.
The parameters depend on the actual command.
A space (blank) is the delimiter for parameters in the command-line.
Commas are used to subdivide parameters. If you need a space inside a parameter,
this parameter has to be enclosed in double quotes (").
Normally, parameters are position dependent, i.e. par1 is the first,
par2 the second, and so on. This may be overridden by using the following
syntax:
command/qualifier P4=par4 P1=par1 P7=par7 ... !comments
If the command procedure which is activated by a MIDAS command uses the
CROSSREF command, it is also possible to execute that command via:
command/qualifier label4=par4 label1=par1 label7=par7 ... !comments
The help text of each command specifies whether such a cross referencing
of parameters is possible and if so, which labels to use.
For details about the command CROSSREF see the description of it in
the section below on MIDAS procedures.
Whenever possible parameters have defaults. If you do not want to override them
use the symbol `?' (question mark) for a parameter if you use the position
dependent format. Therefore,
command/qualifier P4=22.345 is equivalent to
command/qualifier ? ? ? 22.345
The preset default values of MIDAS commands can be overridden with
CREATE/DEFAULTS. For example, the default for the descriptor name(s)
in the READ/DESCR command is
NAXIS,NPIX,START,STEP,IDENT,CUNIT,LHCUTS for an image frame. Thus,
typing
Midas 234> READ/DESCR myimage
will display the contents of the descriptors NAXIS, NPIX, START, STEP, IDENT,
CUNIT and LHCUTS of image myimage.bdf. After changing this default via
Midas 235> CREATE/DEFAULTS READ/DESCR ? HISTORY
the same command
Midas 236> READ/DESCR myimage
will display the contents of the descriptor HISTORY of myimage.bdf.
To abort a MIDAS command, use
(sometimes you also have to hit 
),
which will return control to you.
Note Be careful when aborting commands which interact with a display/graphics window in the X11--Environment. Because you run the risk of losing the synchronisation with the MIDAS display server, which must then be re--initialized via RESET/DISPLAY (see chapter 6 for details).