A complex number can be represented mathematically in rectangular form as $z = x + iy$ or in polar form as $z = re^{i\theta}$. To enter a complex number simply enclose the real and imaginary parts in parenthesis. For example, the complex number $5+3i$ would be entered (in rectangular form) as (5, 3) or (5 3) or in polar form as (5.83, ∡30.96)¹⁾. Alternatively, a complex number can be created from two numbers on the stack using the command R→C:

5 3 R→C

The inverse command to break down a complex number is C→R ²⁾. The real or imaginary parts of a complex number can be returned using the commands RE or IM, respectively. Converting between rectangular and polar representation can be done using the commands →POLAR and →RECT, respectively.

Also, system flag -103 formally sets the calculator mode to complex: -103 SF.

Many of the functions that operate on regular (non-complex) numbers also operate on complex numbers. These functions include the basic arithmetic functions ($+,-,\times,\div$) along with many of the trigonometry ($\sin, \cos, \tan$) and power functions ($x^2, e^x, 10^x$) and their inverses.