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DC(I)                         2/8/75                        DC(I)

     dc - desk calculator

     dc [ file ]

     Dc is an arbitrary precision arithmetic package.  Ordinarily
     it operates on decimal integers, but one may specify an  in-
     put  base, output base, and a number of fractional digits to
     be maintained.  The overall structure 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  stan-
     dard input.  The following constructions are recognized:

           The  value  of  the  number is pushed on the stack.  A
           number is an unbroken string of the  digits  0-9.   It
           may be preceded by an underscore _ to input a negative
           number.  Numbers may contain decimal points.

     +  -  *  %  ^
           The top two values on the stack are  added  (+),  sub-
           tracted  (-), multiplied (*), divided (/), remaindered
           (%), or exponentiated (^).  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

     sx    The  top of the stack is popped and stored into a reg-
           ister named x, where x may be any character.  If the s
           is  capitalized, x is treated as a stack and the value
           is pushed on it.

     lx    The value in register x is pushed on the  stack.   The
           register  x  is not altered.  All registers start with
           zero value.  If the l is capitalized,  register  x  is
           treated  as  a  stack and its top value is popped onto
           the main stack.

     d     The top value on the stack is duplicated.

     p     The top value on the stack is printed.  The top  value
           remains unchanged.

     f     All  values on the stack and in registers are printed.

     q     exits the program.  If executing a string, the  recur-
           sion level is popped by two.  If q is capitalized, the
           top value on the stack is popped and the string execu-
           tion level is popped by that value.

     x     treats  the  top  element  of the stack as a character
           string and executes it as a string of dc commands.

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DC(I)                         2/8/75                        DC(I)

     [ ... ]puts the bracketed ascii string onto the top  of  the

     <x >x =x
           The  top two elements of the stack are popped and com-
           pared.  Register x is executed if they obey the stated

     v     replaces  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

     !     interprets the rest of the line as a UNIX command.

     c     All values on the stack are popped.

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

     o     The  top  value on the stack is popped and used as the
           number radix for further output.

     k     the top of the stack is popped, and that value is used
           as a non-negative scale factor: the appropriate number
           of places are printed on output, and maintained during
           multiplication, division, and exponentiation.  The in-
           teraction of scale factor, input base, and output base
           will be reasonable if all are changed together.

     z     The stack level is pushed onto the stack.

     ?     A line of input is taken from the input source (usual-
           ly the console) and executed.

     An example which prints the first ten values of n! is


     bc(I), which is a preprocessor for dc providing infix nota-
     tion  and  a  C-like  syntax  which implements functions and
     reasonable control structures for programs.

     (x) ? for unrecognized character x.
     (x) ? for not enough elements on the stack to  do  what  was
     asked by command x.
     `Out  of  space'  when  the free list is exhausted (too many
     `Out of headers' for too many numbers being kept around.
     `Out of pushdown' for too many items on the stack.
     `Nesting Depth' for too many levels of nested execution.

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DC(I)                         2/8/75                        DC(I)


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