FIT2D Prompts and Required Input

By default all user prompts are short but further information is always available by entering a question mark (?).

Menu commands may be shortened to any non-ambiguous command; upper, lower, or mixed case input is fine.

Generally prompts propose to the user a default suggestion, and often define a limited range for acceptable input values. Values outside the defined range will not be accepted and FIT2D will re-prompt with a warning message and an explanation of the required input. When a default is given the user can enter $<$ RETURN$>$ to obtain the default value. Default values are used to suggest sensible sizes of values and to guide the user through some of the menu commands.

e.g. To define the X-dimension (horizontal as seen on the screen) the following prompt is issued and information produced to an input which is outside the acceptable range of input:

X DIMENSION FOR ARRAYS (Range: 1 to 1000000) [512]:-1
Must be an integer in the defined range
Here you are asked to define the size of the program arrays.  These will
be used to store data "inside" FIT2D.  Normally you will want the arrays
to be at least as large as the image data to be input. If the dimensions
are larger this does little harm,  but is wasteful of system  resources.
If the arrays are smaller then not all of  an image can be input at full
resolution.  Some input options allow an image to  be re-binned on input
or for a sub-region of the image to be input.
X DIMENSION FOR ARRAYS (Range: 1 to 1000000) [512]:

The return of default values should save you much typing, but leads to a problem for entering blank character strings. If you try to enter a blank character string for a character input which has a default, the default string will be taken. To allow easy input of blank strings a special program variable has been defined: ##BLANK . (Program variables are covered in Section 30.1, Page ). Here all you need know is that a method is available to enter a blank character string. e.g. To set the title of a data-set to be blank the following prompt and input would be used:

Main menu: ENTER COMMAND [GAUSSIAN]:title
NEW TITLE [Simulated Data]:##BLANK

Previously issued commands may be recovered, edited, and re-used using the arrow keys (``command line history recall'') in the same manner as the ``TC-shell'' or emacs. The up-arrow key may be used to go backwards through the ``history'', and the down-arrow key forwards. Once a history line has been selected it may be edited using the left and right-arrow keys, the delete key, and by typing text which will be inserted automatically. The $<$ RETURN$>$ key may be used to enter the whole line of text regardless of the position of the cursor¹¹.

When entering a file name it is possible to type only part of the file name and have the name automatically completed. After typing one or more characters of the file name you may type the <TAB> key and FIT2D will complete or partially complete the file name up to a difference between two file names. If the characters uniquely define a file the name will be completed. emacs uses will be familiar with this functionality as it is provided by the GNU Readline library.

Any text which extends for more than a page (24 lines) is controlled by a ``pager'' which allows forward and backward scrolling and keyword searching.

Generally the user can enter a double backslash ($\backslash$$\backslash$) instead of the normal input to ``escape'' from a particular command¹². This should return the program to the main menu¹³.

Commands may be sent to the operating system from any of the keyboard input menus (V7.26). A dollar needs to be typed before the command to be sent. e.g. To send the command ls -al to a Unix system, you would enter $ls -al. e.g.

Main menu: ENTER COMMAND [IMAGE]:$ls -al

Note: i. Unix systems do not seem to be able to interpret aliases when sending a command in this fashion. ii. Any output to the terminal from the operating system is not included in a log file.