This document serves as a complete description of the GNU Emacs Calculator. It works both as an introduction for novices and as a reference for experienced users. While it helps to have some experience with GNU Emacs in order to get the most out of Calc, this manual ought to be readable even if you don't know or use Emacs regularly. Calc is an advanced calculator and mathematical tool that runs as part of the GNU Emacs environment. Very roughly based on the HP-28/48 series of calculators, its many features include: Choice of algebraic or RPN (stack-based) entry of calculations. Arbitrary precision integers and floating-point numbers. Arithmetic on rational numbers, complex numbers (rectangular and polar), error forms with standard deviations, open and closed intervals, vectors and matrices, dates and times, infinities, sets, quantities with units, and algebraic formulas. Mathematical operations such as logarithms and trigonometric functions. Programmer's features (bitwise operations, non-decimal numbers). Financial functions such as future value and internal rate of return. Number theoretical features such as prime factorization and arithmetic modulo m for any m. Algebraic manipulation features, including symbolic calculus. Moving data to and from regular editing buffers. Embedded mode for manipulating Calc formulas and data directly inside any editing buffer. Graphics using GNUPLOT, a versatile (and free) plotting program. Easy programming using keyboard macros, algebraic formulas, algebraic rewrite rules, or extended Emacs Lisp. Calc tries to include a little something for everyone; as a result it is large and might be intimidating to the first-time user. If you plan to use Calc only as a traditional desk calculator, all you really need to read is the "Getting Started" chapter of this manual and possibly the first few sections of the tutorial. As you become more comfortable with the program you can learn its additional features. Calc does not have the scope and depth of a fully-functional symbolic math package, but Calc has the advantages of convenience, portability, and freedom.