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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 precision arith-
       metic.  It also allows you to define and call macros.  Normally 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 number 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 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
       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 inte-
              ger  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  accom-
              plish 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 anything.  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 preci-
              sion 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 digits 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 different error checking.)

       ^      Pops two values and exponentiates, using the first value popped as the expo-
              nent  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  num-
              ber,  and  should be an integer.  The second popped is used as the exponent;
              this value must be a non-negative number, and any fractional  part  of  this
              exponent  will  be  ignored.   The third value popped is the base which gets
              exponentiated, 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 subtraction 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 character.  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 register 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  out-
       put 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  inclu-
       sive.  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
       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 execu-
              tion 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 num-
              ber of characters, if it is a string) and pushes  that  number.   The  digit
              count  for a number does not include any leading 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 associated 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 AT gnu.org.



GNU Project                       2006-06-11                             dc(1)

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