DC(1)									 DC(1)

NAME
       dc - desk calculator

SYNOPSIS
       dc [ file ]

DESCRIPTION
       Dc  is  an arbitrary precision desk calculator.	Ordinarily it operates
       on decimal integers, but one may specify an input  base,	 output	 base,
       and a number of fractional digits to be maintained.  The overall struc‐
       ture 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.	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 0-9A-F or 0-9a-f.	 A hexadecimal
	      number beginning with a lower case letter must be preceded by  a
	      zero to distinguish it from the command associated with the let‐
	      ter.  It may be preceded by an underscore _ to input a  negative
	      number.  Numbers may contain decimal points.

       +  - /  *  %  ^
	      Add  subtract  multiply divide remainder or exponentiate the top
	      two values on the stack.	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.

       sx
       Sx     Pop the top of the stack and store  into	a  register  named  x,
	      where  x	may be any character.  Under operation S register x is
	      treated as a stack and the value is pushed on it.

       lx
       Lx     Push the value in register x onto the stack.  The register x  is
	      not altered.  All registers start with zero value.  Under opera‐
	      tion L register x is treated as a stack and  its	top  value  is
	      popped onto the main stack.

       d      Duplicate the top value on the stack.

       p      Print  the  top  value  on  the  stack.	The  top value remains
	      unchanged.  P interprets the top of the stack as an text string,
	      removes it, and prints it.

       f      Print the values on the stack.

       q
       Q      Exit the program.	 If executing a string, the recursion level is
	      popped by two.  Under operation Q the top value on the stack  is
	      popped and the string execution level is popped by that value.

       x      Treat  the  top  element	of the stack as a character string and
	      execute it as a string of dc commands.

       X      Replace the number on the top of the stack with its  scale  fac‐
	      tor.

       [ ... ]
	      Put the bracketed text string on the top of the stack.

       <x

       >x

       =x     Pop  and	compare the top two elements of the stack.  Register x
	      is executed if they obey the stated relation.

       v      Replace 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.

       !      Interpret the rest of the line as a shell command.

       c      Clear the stack.

       i      The top value on the stack is popped and used as the number base
	      for further input.

       I      Push the input base on the top of the stack.

       o      The top value on the stack is popped and used as the number base
	      for further output.  In  bases  larger  than  10,	 each  `digit'
	      prints as a group of decimal digits.

       O      Push the output base on the top of the stack.

       k      Pop  the	top of the stack, and use that value 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.

       z      Push the stack level onto the stack.

       Z      Replace the number on the top of the stack with its length.

       ?      A line of input is taken from the input source (usually the ter‐
	      minal) and executed.

       ; :    Used by bc for array operations.

       The scale factor set by k determines how many digits are	 kept  to  the
       right  of  the  decimal point.  If s is the current scale factor, sa is
       the scale of the first operand, sb is the scale of the second, and b is
       the  (integer)  second  operand, results are truncated to the following
       scales.

	      +,-  max(sa,sb)
	      *	   min(sa+sb , max(s,sa,sb))
	      /	   s
	      %	   so that dividend = divisor*quotient + remainder; remainder has sign of dividend
	      ^	   min(sa×|b|, max(s,sa))
	      v	   max(s,sa)

EXAMPLES
       Print the first ten values of n!

	      [la1+dsa*pla10>y]sy
	      0sa1
	      lyx

SOURCE
       /sys/src/cmd/dc.c

SEE ALSO
       bc(1), hoc(1)

DIAGNOSTICS
       x where x is an octal number: an internal error.
       `Out of headers' for too many numbers being kept around.
       `Nesting depth' for too many levels of nested execution.

BUGS
       When the input base exceeds 16, there is no notation for digits greater
       than F.

       Past its time.

									 DC(1)

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