Terminology

The following explain various terms used in this manual.

Keywords

-- global variables in the MIDAS monitor. They can be single numbers or characters or one dimensional arrays used to store input, output, or control information for MIDAS commands.

Frames

-- arrays of numbers representing data values with uniform sampling. They are used for storage of images or spectra.

Images

-- used interchangeably with frames.

Descriptors

-- variables associated to frames, tables or masks describing the contents in them. They are basically the same as keywords just associated to data files instead of the monitor. These descriptors have names like NAXIS (the dimension of the image array), CUNIT (the units of the axes), etc.

Tables

-- two dimensional arrays organised with rows and columns. They are used for storage of heterogeneous data contrary to frames and masks which store homogeneous data. They are typically used for saving lists of e.g. stellar positions and magnitudes. See Chapter 5 for a full description of the table facilities. Many commands output their results or take their input from tables. They constitute a simple data base system for MIDAS.

Catalogues

-- a list of frames, tables, or masks which can be used for input to various commands or merely for reference.

Procedures

-- These are lists of MIDAS commands stored in a file of type filename.prg and which can be executed by typing @@ filename. See Chapter 3 for further details.

Fit file

-- a file that contains the function and parameter values for use in conjunction with the fitting commands described in Chapter 8.