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DC(1)									 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
       parameters are interpreted as the names of input	files to be processed.
       A  file	name  of  - refers to the standard input stream.  The standard
       input will processed if no file names are specified.

Printing Commands
       p      Prints the value on the top of the stack,	without	 altering  the
	      stack.  A	newline	is printed after the 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	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.

       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 subtrac-
       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.

       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	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.

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 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)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | Printing Commands | Arithmetic | Stack Control | Registers | Parameters | Strings | Status Inquiry | Miscellaneous | BUGS

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