dc(1)			    General Commands Manual			 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 (using upper  case  letters  A
       through	F as "digits" when working with input bases greater than ten),
       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 new-
       lines.  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 script files or expressions 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	  KSK0k1/_1Ss	   [ls*]Sxd0>x
	      [256~Ssd0<x]dsxxsx[q]Sq[Lsd0>qaPlxx]  dsxxsx0sqLqsxLxLK+k	 could
	      also accomplish this function.  (Much of the complexity  of  the
	      above  native-dc	code  is due to the ~ computing the characters
	      backwards, and the desire to ensure that all registers  wind  up
	      back in their original states.)

       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.
	      (This can also be accomplished with the sequence SaSbLaLb.)

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  has	a limited ability to 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 num-
       ber 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.  The digit count for a number does not include any lead-
	      ing zeros, even if those appear to the right of the radix point.

       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			  2006-06-11				 dc(1)