### 3.5.7  Configuring the computations

You can configure how Xcas computes by using the menu item CfgCas configuration or by clicking on the status line. You will then be given a window in which you can change the following options:

• Prog style (default: Xcas)
You will have a menu from which you can choose a different language to program in; you can choose from Xcas, Xcas (Python), Maple, Mupad and TI89/92.
• eval (default: 25)
You can type in a positive integer indicating the maximum number of recursions allowed when evaluating expressions.
• prog (default: 1)
You can type in a positive integer indicating the maximum number of recursions allowed when executing programs.
• recurs (default: 100)
You can type in a positive integer indicating the maximum number of recursive calls.
• debug (default: 0)
You can type in an integer, 0 or 1. If this is 1, then Xcas will display intermediate information on the algorithms used by giac. If this number is 0, then no such information is displayed.
• maxiter (default: 20)
You can type in an integer indicating the maximum number of iterations in Newton’s method.
• Float format (default: standard)
You will have a menu from which you can choose how to display decimal numbers. Your choices will be:
• standard In standard notation, a number will be written out completely without using exponentials; for example, 15000.12 will be displayed as 15000.12.
• scientific In scientific notation, a number will be written as a number between 1 and 10 times a power of ten; for example, 15000.12 will be displayed as 1.500012000000e+04 (where the number after e indicates the power of 10).
• engineer In engineer notation, a number will be written as a number between 1 and 1000 times a power of ten, where the power of 10 is a multiple of three. For example, 15000.12 will be displayed as 15.00012e3.
• Digits (default: 12)
You can enter a positive integer which will indicate the number of significant digits.
• epsilon (default: 1e-12)
You can enter a floating point number which will be the value of epsilon used by epsilon2zero, which is a function which replaces numbers with absolute value less than epsilon by 0.
• proba (default: 1e-15)
You can enter a floating point number. If this number is greater than zero, then in some cases giac can use probabilistic algorithms and give a result with probability of being false less than this value. (One such example of a probabilistic algorithm that giac can use is the algorithm to compute the determinant of a large matrix with integer coefficients.)
• approx (default: unchecked)
You will be given a checkbox. If the box is checked, then exact numbers such as √2 will be given a floating point approximation. If the box in unchecked, then exact values will be used when possible.
• autosimplify (default: 1)
You can enter a simplification level of 0, 1 or 2. A value of 0 means no automatic simplification will be done, a value of 1 means grouped simplification will be automatic. A value of 2 means that all simplification will be automatic.
You can enter a positive integer to indicate the number of threads (for a possible future threaded version).
• Integer basis (default: 10)
You will be given a menu from which you can choose an integer base to work in; your choices will be 8, 10 and 16.