The Start-Up of FIT2D

Computer systems should be set-up so that a user can simply type fit2d (in lower case) on the command-line to start it working: e.g.

> fit2d

Additionally the commands fit2d_new, and fit2d_old may be available to start-up a new ``development'' version, or a previous version respectively. (The presence of these versions will depend on the particular site, but sites are recommended to keep the previous version when updating FIT2D in-case the new version leads to problems.) A new window should appear for the FIT2D graphics, and the FIT2D ``banner page'' should appear within the window. (The start-up may fail for a number of different reasons. These are explained in Section 10 together with advice on ways to circumvent problems.)

The ``banner page'' and the terminal window contain some general information, including the version number of FIT2D which is being used. The ``banner page'' also contains four buttons:

HELP Help text on the general use of FIT2D and in particular on the banner page.

CONDITIONS Text explaining the ``conditions of use'' for FIT2D.

I ACCEPT Accept the ``conditions of use'', and entering the main part of the program.

DON'T ACCEPT Refuse the ``conditions of use'' and exit FIT2D.

Having accepted the ``conditions of use'', a ``graphical form'' appears. This form, allows the size of internal program arrays to be set. FIT2D uses ``dynamic allocation'' of program arrays to allow enormous flexibility in the size of data-sets which may be treated. Normally only the size of the internal arrays in the ``X-direction'' (horizontal) and ``Y-direction'' (vertical) need to be set. These dimensions should normally be set as large, or larger than the size of the data to be input, but smaller arrays may be used, with the consequence that not all the data may be input at full resolution.

A ``Memory'' array, to allow a second image to be stored within FIT2D, is created by default, but doubles the computer memory demands for the internal program arrays so may be disabled. By default ``memory'' arrays are created since most commands depend on the existence of the ``memory''.

It is also possible to create ``variance'' arrays which allow error propagation to be carried out, and weighted fitting to be performed. However, this doubles again the requirements for computer memory, and operations will take twice as long or longer. By default variance arrays are not created.

(It is possible to avoid this form completely, by specifying this information using ``command-line options'' (see Section 9).)