NAME

dc − desk calculator

SYNOPSIS

dc [ file ]

DESCRIPTION

The command Dc is an arbitrary precision arithmetic package.  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 structure of dc is a stacking (reverse Polish) calculator.  If an argument is given, input is taken both from that file until its end and 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 through 9. A number may be preceded by an underscore _ to input a negative number and numbers may contain decimal points.

+  − /  \(**  %  ^
The top two values on the stack are added (+), subtracted (−), 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 ignored.

sx The top of the stack is popped and stored into a register 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 X. 

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.  P interprets the top of the stack as an ASCII string P then removes and prints the top of the stack. 

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

q Exits the program.  If executing a string, the recursion level is popped by two.  If q is capitalized, the top value on the stack is popped and the string execution level is popped by that value. 

x Treats the top element of the stack as a character string and executes this element as a string of dc commands. 

X Replaces the number on top of the stack with the number’s scale factor. 

[ ... ] Puts the bracketed ASCII string on top of the stack. 

<x  >x  =x
The top two elements of the stack are popped and compared. Register x is executed if the two elements obey the stated relation. 

v Replaces the top element on the stack by its square root.  Any existing fractional part of the argument is considered, but otherwise, the scale factor is ignored. 

!  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.  I pushes the input base on top of the stack. 

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

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

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 interaction of scale factor, input base, and output base are adequate if all are changed together. 

K Pushes back the value last popped by k onto the stack.  If k was not used, the top value of the stack is duplicated onto the stack. 

z The stack level is pushed onto the stack. 

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

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

; : used by bc for array operations. 

The following is an example which prints the first ten values of n! is

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

SEE ALSO

bc(1), which is a preprocessor for dc providing infix notation and a C-like syntax which implements functions and reasonable control structures for programs. 

DIAGNOSTICS

‘x is unimplemented’ where x is an octal number. 
‘stack empty’ for not enough elements on the stack fulfill request.
‘Out of space’ when the free list is exhausted (too many digits).
‘Out of headers’ for too many numbers being maintained.
‘Out of pushdown’ for too many items on the stack.
‘Nesting Depth’ for too many levels of nested execution.

October 24, 1983  —  %W%%Q%%Y%