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dc(1)

NAME

       dc - an arbitrary precision calculator

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 preci-
       sion arithmetic.  It also allows you to define and call	macros.   Nor-
       mally  dc  reads  from the standard 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 standard error.

       A reverse-polish calculator stores numbers on a stack.  Entering a num-
       ber  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 succession, 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

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

       If any command-line parameters remain after processing the above, these
       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 clobbering the x register.

       f      Prints  the  entire  contents of the stack without altering any-
	      thing.  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  dig-
	      its is specified by the precision 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 computed 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 number of fraction digits used in the division
	      is specified by the precision value.  (The sequence  SdSn  lnld/
	      LnLd% could also accomplish this function, with slightly differ-
	      ent error checking.)

       ^      Pops two values and exponentiates, using the first value	popped
	      as the exponent and the second popped as the base.  The fraction
	      part of the exponent is ignored.	The precision value  specifies
	      the number of fraction digits in the result.

       |      Pops  three  values  and computes a modular exponentiation.  The
	      first value popped is used as the reduction modulus; this  value
	      must be a non-zero number, and should be an integer.  The second
	      popped is used as the exponent; this value must be  a  non-nega-
	      tive  number,  and  any fractional part of this exponent will be
	      ignored.	The third value popped is the base which gets exponen-
	      tiated,  which should be an integer.  For small integers this is
	      like the sequence Sm^Lm%, but, unlike ^, this command will  work
	      with arbitrarily large exponents.
       tion produces integer results.

Stack Control

       c      Clears the stack, rendering it empty.

       d      Duplicates the value on the top of the  stack,  pushing  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 char-
       acter.  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 regis-
	      ter 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 in the result of most arithmetic operations.
       The  input  radix  controls the interpretation of numbers typed in; all
       numbers typed in use this radix.  The output radix is used for printing
       numbers.

       The input and output radices are separate parameters; you can make them
       unequal, which can be useful or confusing.  The	input  radix  must  be
       between	2 and 16 inclusive.  The output radix must be at least 2.  The
       precision must be zero or greater.  The precision is always measured in
       decimal digits, regardless of the current input or output radix.

       i      Pops  the  value off the top of the stack and uses it 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.
       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 characters 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 character 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 of register r as a macro  if
	      the  original  top-of-stack is greater.  Thus, 1 2>a will invoke
	      register a's contents and 2 1>a will not.

       !>r    Similar but invokes the macro if the  original  top-of-stack  is
	      not greater than (less than or equal to) what was the second-to-
	      top.

       <r     Similar but invokes the macro if the  original  top-of-stack  is
	      less.

       !<r    Similar  but  invokes  the macro if the original top-of-stack is
	      not less than (greater than or equal to) what was the second-to-
	      top.

       =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.


       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 array associ-
       ated with it.  Thus 1 0:a 0Sa 2 0:a La 0;ap will print 1, because the 2
       was stored in an instance of 0:a that was later popped.

BUGS

       Email bug reports to bug-dc@gnu.org.

GNU Project			  1997-03-25				 DC(1)

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