CAL is an inline geometry calculator that evaluates point (vector), real, or integer
expressions. The expressions can access existing geometry using the object snap functions
such as CEN, END, and INS.

You can insert AutoLISP ^آ® variables into the arithmetic expression and assign the value of the expression back
to an AutoLISP variable. You can use these arithmetic and vector expressions in any
command that expects points, vectors, or numbers. (Not available in AutoCAD LT.)