An arbitrary precision calculator. Uses reverse polish notation (RPN).

# To run calculator in interactive mode:
dc

# To execute dc script in 'file':
dc -f file

# To calculate 4 times 5 [4 5 *], subtract 17 [17 -], and [p]rint the output (using echo):
echo "4 5 * 17 - p"| dc

# To set number of decimal places to 7 [7 k], calculate 5 divided by -3 [5 _3 /] and [p]rint (using dc -e):
dc -e "7 k 5 _3 / p"

# To calculate the golden ratio, phi: Set number of decimal places to 100 [100 k], square root of 5 [5 v] plus 1 [1 +], divided by 2 [2 /], and [p]rint result:
dc -e "100 k 5 v 1 + 2 / p"