Dc is an arbitrary precision desk calculator. Ordinarily it
operates on decimal integers, 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:
- number
- The value of the number is pushed on the stack. A number is an unbroken
string of the digits 0-9A-F or 0-9a-f. A hexadecimal number
beginning with a lower case letter must be preceded by a zero to
distinguish it from the command associated with the letter. It may be
preceded by an underscore _ to input a negative number. Numbers may
contain decimal points.
- + - / * % ^
- Add subtract multiply divide remainder or exponentiate the top two values
on the stack. 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
-
- Sx
- Pop the top of the stack and store into a register named x, where
x may be any character. Under operation S register x
is treated as a stack and the value is pushed on it.
- lx
-
- Lx
- Push the value in register x onto the stack. The register x
is not altered. All registers start with zero value. Under operation
L register x is treated as a stack and its top value is
popped onto the main stack.
- d
- Duplicate the top value on the stack.
- p
- Print the top value on the stack. The top value remains unchanged.
P interprets the top of the stack as an text string, removes it,
and prints it.
- f
- Print the values on the stack.
- q
-
- Q
- Exit the program. If executing a string, the recursion level is popped by
two. Under operation Q the top value on the stack is popped and the
string execution level is popped by that value.
- x
- Treat the top element of the stack as a character string and execute it as
a string of dc commands.
- X
- Replace the number on the top of the stack with its scale factor.
- [ ... ]
- Put the bracketed text string on the top of the stack.
- <x
- >x
- =x
- Pop and compare the top two elements of the stack. Register x is
executed if they obey the stated relation.
- v
- Replace 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 ignored.
- !
- Interpret the rest of the line as a shell command.
- c
- Clear the stack.
- i
- The top value on the stack is popped and used as the number base for
further input.
- I
- Push the input base on the top of the stack.
- o
- The top value on the stack is popped and used as the number base for
further output. In bases larger than 10, each `digit' prints as a group of
decimal digits.
- O
- Push the output base on the top of the stack.
- k
- Pop the top of the stack, and use that value as a non-negative scale
factor: 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
- Push the stack level onto the stack.
- Z
- Replace 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.
- ; :
- Used by bc for array operations.
The scale factor set by k determines how many digits are
kept to the right of the decimal point. If s is the current scale
factor, sa is the scale of the first operand, sb is the scale
of the second, and b is the (integer) second operand, results are
truncated to the following scales.
-
+,- max(sa,sb)
* min(sa+sb , max(s,sa,sb))
/ s
% so that dividend = divisor*quotient + remainder; remainder has sign of dividend
^ min(sa×|b|, max(s,sa))
v max(s,sa)
Print the first ten values of n!
-
[la1+dsa*pla10>y]sy
0sa1
lyx
x where x is an octal number: an internal error.
`Out of headers' for too many numbers being kept around.
`Nesting depth' for too many levels of nested execution.
When the input base exceeds 16, there is no notation for digits
greater than F.
Past its time.