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DC(1)                   FreeBSD General Commands Manual                  DC(1)

NAME
       dc, An Arbitrary Precision Calculator

SYNOPSIS
       dc

DESCRIPTION
       DC is a reverse-polish desk calculator which supports unlimited
       precision arithmetic.  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 output is to
       standard output.

       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, 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.

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

       P Prints the value on the top of the stack, popping it off, and does
       not print a newline after.

       f Prints the entire contents of the stack and the contents of all of
       the registers, 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
       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 is controlled by the current precision
       flag (see below) and does not depend on the values being multiplied.

       / 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 flag.

       % Pops two values, computes the remainder of the division that the /
       command would do, and pushes that.  The division is done with as many
       fraction digits as the precision flag specifies, and the remainder is
       also computed with that many fraction digits.

       ^ 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 flag specifies the number of
       fraction digits in the result.

       v Pops one value, computes its square root, and pushes that.  The
       precision flag specifies the number of fraction digits in the result.

       Most arithmetic operations are affected by the "precision flag", 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.

       The remainder operation % requires some explanation: applied to
       arguments `a' and `b' it produces `a - (b * (a / b))', where `a / b' is
       computed in the current precision.

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.

Registers
       DC provides 128 memory registers, each named by a single ASCII
       character.  You can store a number 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 Ir command.

       The f command prints a list of all registers that have contents stored
       in them, together with their contents.  Only the current contents of
       each register (the top of its stack) is printed.

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;
       allnumbers 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.  Each radix must be between
       2 and 36 inclusive.  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

       k Similarly set the output radix and the precision.

       I Pushes the current input radix on the stack.

       O

       K Similarly push the current output radix and the current precision.

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).
       Both 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 and pushes it on the
       stack.  For example, [foo]p prints the characters foo (with no
       newline).

       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 the 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 less.

       =r Similar but invokes the macro if the two numbers popped are equal.
       This can also be validly used to compare two strings for equality.

       ?  Reads a line from the terminal and executes it.  This command allows
       a macro to request input from the user.

       q During the execution of a macro, this comand does not exit DC.
       Instead, it exits from that macro and also from the macro which invoked
       it (if any).

       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.

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 -1.

       z Pushes the current stack depth; the number of objects on the stack
       before the execution of the z command.

       I Pushes the current value of the input radix.

       O Pushes the current value of the output radix.

       K Pushes the current value of the precision.

Notes
       The : and ; commands of the Unix DC program are not supported, as the
       documentation does not say what they do.  The ! command is not
       supported, but will be supported as soon as a library for executing a
       line as a command exists.

BUGS
       Email bug reports to bug-gnu-utils@prep.ai.mit.edu.  Be sure to include
       the word ``dc'' somewhere in the ``Subject:'' field.

GNU Project                       03 Aug 1993                            DC(1)

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

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