## SYNOPSIS

           dc [-V] [--version] [-h] [--help]
              [-e scriptexpression] [--expression=scriptexpression]
              [-f scriptfile] [--file=scriptfile]
              [file ...]

## DESCRIPTION

           Dc  is  a  reverse-polish  desk  calculator which supports
           unlimited precision arithmetic.  It  also  allows  you  to
           define  and call macros.  Normally dc reads from the stan
           dard input; if any command arguments are given to it, they
           are  filenames,  and dc reads and executes the contents of
           the files before reading from standard input.  All  normal
           output is to standard output; all error output is to stan
           dard error.

           A reverse-polish calculator stores  numbers  on  a  stack.
           Entering  a  number  pushes  it  on the stack.  Arithmetic
           operations pop  arguments  off  the  stack  and  push  the
           results.

           To  enter a number in dc, type the digits with an optional
           decimal point.  Exponential notation is not supported.  To
           enter  a  negative  number,  begin  the number with ``_''.
           ``-'' cannot be used for this, as it is a binary  operator
           for  subtraction instead.  To enter two numbers in succes
           sion, separate them with spaces or newlines.   These  have
           no meaning as commands.

## OPTIONS

           Dc may be invoked with the following command-line options:

           -V

           --version
                  Print out the version of dc that is being run and a
                  copyright notice, then exit.

           -h

           --help Print  a  usage  message  briefly summarizing these
                  command-line options and the bug-reporting address,
                  then exit.

           -e script

           --expression=script
                  Add  the  commands in script to the set of commands
                  to be run while processing the input.

           -f script-file

                  value.

           n      Prints the value on the top of the  stack,  popping
                  it off, and does not print a newline after.

           P      Pops off the value on top of the stack.  If it it a
                  string, it is simply  printed  without  a  trailing
                  newline.  Otherwise it is a number, and the integer
                  portion of its absolute value is printed out  as  a
                  "base  (UCHAR_MAX+1)"  byte  stream.  Assuming that
                  (UCHAR_MAX+1) is 256 (as it  is  on  most  machines
                  with  8-bit  bytes),  the sequence KSK 0k1/ [_1*]sx
                  d0>x [256~aPd0<x]dsxx sxLKk could  also  accomplish
                  this  function, except for the side-effect of clob
                  bering the x register.

           f      Prints the entire contents  of  the  stack  without
                  altering  anything.   This is a good command to use
                  if you are lost or want  to  figure  out  what  the
                  effect of some command has been.

## Arithmetic

           +      Pops  two  values  off  the  stack,  adds them, and
                  pushes the result.  The precision of the result  is
                  determined only by the values of the arguments, and
                  is enough to be exact.

           -      Pops two values, subtracts  the  first  one  popped
                  from  the second one popped, and pushes the result.

           *      Pops two values, multiplies them,  and  pushes  the
                  result.   The  number  of  fraction  digits  in the
                  result depends on the current precision  value  and
                  the number of fraction digits in the two arguments.

           /      Pops two values, divides the second one popped from
                  the  first  one popped, and pushes the result.  The
                  number of fraction digits is specified by the  pre
                  cision value.

           %      Pops  two  values,  computes  the  remainder of the
                  division that the / command would  do,  and  pushes
                  that.   The value computed is the same as that com
                  puted by the sequence Sd dld/ Ld*- .

           ~      Pops two values, divides the second one popped from
                  the  first  one  popped.   The  quotient  is pushed
                  first, and the remainder is pushed next.  The  num
                  ber  of  fraction  digits  used  in the division is
                  specified by the precision  value.   (The  sequence
                  SdSn  lnld/  LnLd% could also accomplish this func
                  tion, with slightly different error checking.)
                  popped  is the base which gets exponentiated, which
                  should be an integer.  For small integers  this  is
                  like  the sequence Sm^Lm%, but, unlike ^, this com
                  mand will work with arbitrarily large exponents.

           v      Pops one  value,  computes  its  square  root,  and
                  pushes  that.   The  precision  value specifies the
                  number of fraction digits in the result.

           Most arithmetic operations are affected by the ``precision
           value'',  which  you  can  set  with  the  k command.  The
           default precision value is  zero,  which  means  that  all
           arithmetic  except  for  addition and subtraction produces
           integer results.

## Stack Control

           c      Clears the stack, rendering it empty.

           d      Duplicates the value on the top of the stack, push
                  ing  another copy of it.  Thus, ``4d*p'' computes 4
                  squared and prints it.

           r      Reverses the order of (swaps) the top two values on
                  the stack.

## Registers

           Dc provides at least 256 memory registers, each named by a
           single character.  You can store a number or a string in a
           register and retrieve it later.

           sr     Pop the value off the top of the stack and store it
                  into register r.

           lr     Copy the value in register r and push it  onto  the
                  stack.  This does not alter the contents of r.

           Each  register  also  contains its own stack.  The current
           register value is the top of the register's stack.

           Sr     Pop the value off the top of the (main)  stack  and
                  push it onto the stack of register r.  The previous
                  value of the register becomes inaccessible.

           Lr     Pop the value off the top of register r's stack and
                  push it onto the main stack.  The previous value in
                  register r's stack, if any, is now  accessible  via
                  the lr command.

## Parameters

           Dc  has  three  parameters that control its operation: the
           precision, the input radix, and  the  output  radix.   The
           precision  specifies the number of fraction digits to keep
                  to set the input radix.

           o      Pops the value off the top of the stack and uses it
                  to set the output radix.

           k      Pops the value off the top of the stack and uses it
                  to set the precision.

           I      Pushes the current input radix on the stack.

           O      Pushes the current output radix on the stack.

           K      Pushes the current precision on the stack.

## Strings

           Dc can operate on strings as well as on numbers.  The only
           things  you can do with strings are print them and execute
           them as macros (which  means  that  the  contents  of  the
           string  are  processed as dc commands).  All registers and
           the stack can hold strings, and dc  always  knows  whether
           any  given  object is a string or a number.  Some commands
           such as arithmetic operations demand numbers as  arguments
           and  print  errors  if  given strings.  Other commands can
           accept either a number or a string;  for  example,  the  p
           command  can accept either and prints the object according
           to its type.

           [characters]
                  Makes a  string  containing  characters  (contained
                  between balanced [ and ] characters), and pushes it
                  on the stack.  For example, [foo]P prints the char
                  acters foo (with no newline).

           a      The  top-of-stack  is  popped.  If it was a number,
                  then the low-order byte of this number is converted
                  into a string and pushed onto the stack.  Otherwise
                  the top-of-stack was a string, and the first  char
                  acter of that string is pushed back.

           x      Pops  a  value  off  the stack and executes it as a
                  macro.  Normally it should be a string; if it is  a
                  number,  it  is  simply pushed back onto the stack.
                  For example, [1p]x  executes  the  macro  1p  which
                  pushes  1  on  the stack and prints 1 on a separate
                  line.

           Macros are most often stored in registers; [1p]sa stores a
           macro  to  print  1  into register a, and lax invokes this
           macro.

           >r     Pops two values off the  stack  and  compares  them
                  assuming  they  are numbers, executing the contents

           =r     Similar  but  invokes  the macro if the two numbers
                  popped are equal.

           !=r    Similar but invokes the macro if  the  two  numbers
                  popped are not equal.

           ?      Reads  a  line  from  the terminal and executes it.
                  This command allows a macro to request  input  from
                  the user.

           q      exits  from  a  macro and also from the macro which
                  invoked it.  If called from the top level, or  from
                  a  macro  which  was  called  directly from the top
                  level, the q command will cause dc to exit.

           Q      Pops a value off the stack and uses it as  a  count
                  of  levels  of macro execution to be exited.  Thus,
                  3Q exits three levels.  The Q  command  will  never
                  cause dc to exit.

## Status Inquiry

           Z      Pops  a  value off the stack, calculates the number
                  of digits it has (or number of characters, if it is
                  a string) and pushes that number.

           X      Pops  a  value off the stack, calculates the number
                  of fraction digits it has, and pushes that  number.
                  For a string, the value pushed is 0.

           z      Pushes  the  current  stack  depth:  the  number of
                  objects on the stack before the execution of the  z
                  command.

## Miscellaneous

           !      Will  run the rest of the line as a system command.
                  Note that parsing of the !<, !=,  and  !>  commands
                  take  precedence,  so  if you want to run a command
                  starting with <, =, or > you will  need  to  add  a
                  space after the !.

           #      Will interpret the rest of the line as a comment.

           :r     Will  pop the top two values off of the stack.  The
                  old second-to-top value will be stored in the array
                  r, indexed by the old top-of-stack value.

           ;r     Pops  the top-of-stack and uses it as an index into
                  the array r.  The selected  value  is  then  pushed
                  onto the stack.

           Note  that each stacked instance of a register has its own