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#### 6.8.2 C, FORTRAN, and Pascal Modes

The d C (`calc-c-language`) command selects the conventions of the C language for display and entry of formulas. This differs from the normal language mode in a variety of (mostly minor) ways. In particular, C language operators and operator precedences are used in place of Calc's usual ones. For example, ‘a^b’ means ‘xor(a,b)’ in C mode; a value raised to a power is written as a function call, ‘pow(a,b)’.

In C mode, vectors and matrices use curly braces instead of brackets. Octal and hexadecimal values are written with leading ‘0’ or ‘0x’ rather than using the ‘#’ symbol. Array subscripting is translated into `subscr` calls, so that ‘a[i]’ in C mode is the same as ‘a_i’ in Normal mode. Assignments turn into the `assign` function, which Calc normally displays using the ‘:=’ symbol.

The variables `pi` and `e` would be displayed ‘pi’ and ‘e’ in Normal mode, but in C mode they are displayed as ‘M_PI’ and ‘M_E’, corresponding to the names of constants typically provided in the <math.h> header. Functions whose names are different in C are translated automatically for entry and display purposes. For example, entering ‘asin(x)’ will push the formula ‘arcsin(x)’ onto the stack; this formula will be displayed as ‘asin(x)’ as long as C mode is in effect.

The d P (`calc-pascal-language`) command selects Pascal conventions. Like C mode, Pascal mode interprets array brackets and uses a different table of operators. Hexadecimal numbers are entered and displayed with a preceding dollar sign. (Thus the regular meaning of \$2 during algebraic entry does not work in Pascal mode, though \$ (and \$\$, etc.) not followed by digits works the same as always.) No special provisions are made for other non-decimal numbers, vectors, and so on, since there is no universally accepted standard way of handling these in Pascal.

The d F (`calc-fortran-language`) command selects FORTRAN conventions. Various function names are transformed into FORTRAN equivalents. Vectors are written as ‘/1, 2, 3/’, and may be entered this way or using square brackets. Since FORTRAN uses round parentheses for both function calls and array subscripts, Calc displays both in the same way; ‘a(i)’ is interpreted as a function call upon reading, and subscripts must be entered as ‘subscr(a, i)’. If the variable `a` has been declared to have type `vector` or `matrix`, however, then ‘a(i)’ will be parsed as a subscript. (See Declarations.) Usually it doesn't matter, though; if you enter the subscript expression ‘a(i)’ and Calc interprets it as a function call, you'll never know the difference unless you switch to another language mode or replace `a` with an actual vector (or unless `a` happens to be the name of a built-in function!).

Underscores are allowed in variable and function names in all of these language modes. The underscore here is equivalent to the ‘#’ in Normal mode, or to hyphens in the underlying Emacs Lisp variable names.

FORTRAN and Pascal modes normally do not adjust the case of letters in formulas. Most built-in Calc names use lower-case letters. If you use a positive numeric prefix argument with d P or d F, these modes will use upper-case letters exclusively for display, and will convert to lower-case on input. With a negative prefix, these modes convert to lower-case for display and input.