### 2.5.10 Configuration file

When you save changes to your configuration, they are stored in a configuration file, which will be .xcasrc in your home directory in Unix and xcas.rc in Windows. This file will have four functions – widget_size, cas_setup, xcas_mode and xyztrange – which determine the configuration and which are evaluated when Xcas starts.

The widget_size command sets properties of the opening Xcas window.

- widget_size takes between 1 and 12 arguments. The arguments (in order) are:
  Font size.
    The first argument is a positive integer specifying the font size. Optionally, this can be a bracketed list whose first number indicates the font and the second the font size.
  Horizontal and vertical offset.
    The second and third arguments are horizontal and vertical distances in pixels from the upper left hand corner of the screen. They specify where the upper left corner of the Xcas window is when it opens.
  Window size.
    The fourth and fifth arguments specify the width and height in pixels of the Xcas window when it opens.
  Keyboard
    (see Section 2.2, item 2.2). The sixth argument is either 0 or 1; a 1 indicates that the on-screen keyboard will be open when Xcas starts, a 0 indicates that the keyboard will be hidden.
  Open browser.
    The seventh argument is either 0 or 1; a 1 indicates that the browser will be automatically opened to display help for the selected command in the menu or index, a 0 indicates that the browser will not be automatically opened.
  Message window
    (see Section 2.2, item 2.2). The eighth argument is either 0 or 1; a 1 indicates that Xcas will open with the message window, a 0 indicates that Xcas will open without the message window.
  <empty>.
    The ninth argument is currently not used.
  Browser name.
    The tenth argument is a string with the name of the browser to use to read the help pages. A value of "builtin" means that Xcas will use a small browser built into Xcas.
  Starting level
    (see Section 2.1). The eleventh argument indicates what level Xcas will start at; a 0 means command line, a 1 means program editor, a 2 means spreadsheet, and a 3 means a 2D geometry screen.
  Postscript previewer.
    The twelfth argument is a string with the name of a program for postscript previews; for example, "gv".

The cas_setup command determines how computations will be performed.

- cas_setup takes nine arguments. The arguments (in order) are:
  Approximate mode
    (see Section 2.5.4). A 1 means Xcas works in approximate mode, a 0 means exact mode.
  Complex variables
    (see Section 2.5.5). A 1 means Xcas works with complex variables, a 0 means real variables.
  Complex mode
    (see Section 2.5.5). A 1 means Xcas works with in complex mode, a 0 means real mode.
  Radian
    (see Section 2.5.3). A 1 means work in radians, a 0 means work in degrees.
  Display format
    (see Section 2.5.7, item 2.5.7). A 0 means use the standard format to display numbers, a 1 means use scientific format, a 2 means use engineering format, and a 3 means use floating hexadecimal format (which is standardized with a non-zero first digit).
  Epsilon
    (see Section 2.5.7, item 2.5.7). This is the value of epsilon used by Xcas.
  Digits.
    This is the number of digits to use to display a float.
  Tasks.
    This will be used in the future for parallelism.
  Increasing power.
    This is 0 to display polynomials in increasing power, and 1 to display polynomials in decreasing powers.

The xcas_mode command sets the computer language used by Xcas (see Section 2.5.2).

The xyztrange command sets or returns the values of the graphics configuration.

- To set the values, xyztrange takes 15 arguments:
  - x– and x+, the beginning and the end of the x interval for which calculations will be done.
  - y– and y+, the beginning and the end of the y interval for which calculations will be done.
  - z– and z+, the beginning and the end of the z interval for which calculations will be done.
  - t– and t+, the beginning and the end of the t interval for which calculations will be done, when plotting parametric curves, for example.
  - wx– and wx+, the beginning and the end of the x values for the viewing window.
  - wy– and wy+, the beginning and the end of the y values for the viewing window.
  - show_axes, to determine whether axes are shown or hidden (1 to show, 0 to hide).
  - class_min, the minimum size of a statistics class.
  - class_size, the default size of a statistics class.
- xyztrange(x–,x+,y–,y+,z–,z+, t–,t+,wx–,wx+,wy–,wy+,show_axes, class_min,class_size) sets the parameters to the given values.

  Note that the viewing window is not the same as the calculation window; if the calculation window is larger than the visible window, then you can scroll to bring other parts of the calculation window into view.

- To return the values, xyztrange takes no arguments.
- xyztrange() returns a matrix where each row consists of a short description of the first twelve arguments along with their values.