C[i] is the default form for the i parameter or constant generated in representing the results of various symbolic computations.
The C[i] are often used to parameterize families of solutions to equations.
In functions like DSolve, the C[i] can be thought of as corresponding to constants of integration.
In cases such as partial differential equations, the C[i] represent functions rather than variables.
C is the default setting for the option GeneratedParameters in such functions as DSolve, RSolve and Reduce.
See Section 1.5.9 and Section 3.5.10.
See also: GeneratedParameters, Unique.
New in Version 2.