dc - desk calculator
dc is an arbitrary precision arithmetic package. Ordinarily it
operates on decimal integers, but one may specify an input base,
output base, and a number of fractional digits to be maintained. (See
bc(1), a preprocessor for dc that provides infix notation and a C-like
syntax that implements functions. bc also provides reasonable control
structures for programs.) 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. An end of
file on standard input or the q command stop dc. 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 0-9 or
A-F. It can be preceded by an underscore (_) to
input a negative number. Numbers can contain
+ - / * % ^ 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 and a
warning generated. The remainder is calculated
according to the current scale factor; it is not
the integer modulus function. 7 % 3 yields .1
(one tenth) if scale is 1 because 7 / 3 is 2.3
with .1 as the remainder.
sx The top of the stack is popped and stored into a
register named x, where x can 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.
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 interprets the top of
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the stack as an ASCII string, removes it, and
f All values on the stack 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
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. Strings can be nested by using nested
pairs of brackets.
<<<<x >>>>x =x
!<<<<x !>>>>x !=x
The top two elements of the stack are popped and
compared. Register x is evaluated 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 ignored.
! Interprets the rest of the line as an HP-UX system
command (unless the next character is <<<<, >>>>, or =,
in which case appropriate relational operator
above is used).
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 output. See below
for notes on output base.
O pushes the output base on the top of the stack.
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k the top of the stack is popped, and that value is
used 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.
K pushes the scale factor on the top of the stack.
z The stack level is pushed onto the stack.
Z replaces the number on the top of the stack with
? A line of input is taken from the input source
(usually the terminal) and executed.
; and : Used by bc for array operations.
Y Generates debugging output for dc itself.
The input base may be any number, but only the digits 0-9 and A-F are
available for input, thus limiting the usefulness of bases outside the
range 1-16. All 16 possible digits may be used in any base; they
always take their conventional values.
The output base may be any number. Bases in the range of 2-16
generate the "usual" results, with the letters A-F representing the
values from 10 through 16. Bases 0 and 1 generate a string of 1s
whose length is the value of the number. Base -1 generates a similar
string consisting of ds. Other bases have each "digit" represented as
a (multi-digit) decimal number giving the ordinal of that digit. Each
"digit" is signed for negative bases. "Digits" are separated by
spaces. Given the definition of output base, the command Op always
yields "10" (in a representation appropriate to the base); O1-p yields
useful information about the output base.
x is unimplemented Where x is an octal number.
stack empty There are insufficient elements on the
stack to do what was asked.
Out of space The free list is exhausted (too many
Out of headers Too many numbers are being kept around.
Out of pushdown Too many items are on the stack.
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Nesting Depth There are too many levels of nested
This example prints the first ten values of n! (n factorial):
DC: An Interactive Desk Calculator tutorial in Number Processing Users
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