dc - desk calculator
dc [ file ]
Dc is an arbitrary precision arithmetic package. Ordinarily it operates on decimal inte-
gers, but one may specify an input base, output base, and a number of fractional digits to
be maintained. The overall structure of dc is a stacking (reverse Polish) calculator. If
an argument is given, input is taken from that file until its end, then from the standard
input. The following constructions are recognized:
The value of the number is pushed on the stack. A number is an unbroken string of
the digits 0-9. It may be preceded by an underscore _ to input a negative number.
Numbers may contain decimal points.
+ - / * % ^
The top two values on the stack are added (+), subtracted (-), multiplied (*),
divided (/), remaindered (%), or exponentiated (^). The two entries are popped off
the stack; the result is pushed on the stack in their place. Any fractional part of
an exponent is ignored.
sx The top of the stack is popped and stored into a register named x, where x may be
any character. If the s is capitalized, x is treated as a stack and the value is
pushed on it.
lx The value in register x is pushed on the stack. The register x is not altered. All
registers start with zero value. If the l is capitalized, register x is treated as
a stack and its top value is popped onto the main stack.
d The top value on the stack is duplicated.
p The top value on the stack is printed. The top value remains unchanged. P inter-
prets the top of the stack as an ascii string, removes it, and prints it.
f All values on the stack and in registers are printed.
q exits the program. If executing a string, the recursion level is popped by two. If
q is capitalized, the top value on the stack is popped and the string execution
level is popped by that value.
x treats the top element of the stack as a character string and executes it as a
string of dc commands.
X replaces the number on the top of the stack with its scale factor.
[ ... ]
puts the bracketed ascii string onto the top of the stack.
<x >x =x
The top two elements of the stack are popped and compared. Register x is executed
if they obey the stated relation.
v replaces the top element on the stack by its square root. Any existing fractional
part of the argument is taken into account, but otherwise the scale factor is
! interprets the rest of the line as a UNIX command.
c All values on the stack are popped.
i The top value on the stack is popped and used as the number radix for further input.
I pushes the input base on the top of the stack.
o The top value on the stack is popped and used as the number radix for further out-
O pushes the output base on the top of the stack.
k the top of the stack is popped, and that value is used as a non-negative scale fac-
tor: the appropriate number of places are printed on output, and maintained during
multiplication, division, and exponentiation. The interaction of scale factor,
input base, and output base will be reasonable if all are changed together.
z The stack level is pushed onto the stack.
Z replaces the number on the top of the stack with its length.
? A line of input is taken from the input source (usually the terminal) and executed.
; : are used by bc for array operations.
An example which prints the first ten values of n! is
bc(1), which is a preprocessor for dc providing infix notation and a C-like syntax which
implements functions and reasonable control structures for programs.
`x is unimplemented' where x is an octal number.
`stack empty' for not enough elements on the stack to do what was asked.
`Out of space' when the free list is exhausted (too many digits).
`Out of headers' for too many numbers being kept around.
`Out of pushdown' for too many items on the stack.
`Nesting Depth' for too many levels of nested execution.
7th Edition April 29, 1985 DC(1)