The most straightforward way to extract the stored value from a variable
is to use the s r (calc-recall) command. This command prompts
for a variable name (similarly to calc-store), looks up the value
of the specified variable, and pushes that value onto the stack. It is
an error to try to recall a void variable.
It is also possible to recall the value from a variable by evaluating a formula containing that variable. For example, ' a RET = is the same as s r a RET except that if the variable is void, the former will simply leave the formula `a' on the stack whereas the latter will produce an error message.
The r prefix may be followed by a digit, so that r 9 is equivalent to s r 9. (The r prefix is otherwise unused in the current version of Calc.)