dc(1)
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dc Command
desk calculator
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SYNTAX
dc [ file ]
DESCRIPTION
Dc is an arbitrary precision arithmetic package. Ordinarily it
operates on decimal integers, but you can specify an input base,
output base, and a number of fractional digits to be maintained.
(See bc(1), a preprocessor for dc that provides infix notation
and a C-like syntax that implements functions. Bc also provides
reasonable control structures for programs.) 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 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 0-9. 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 (+), subtracted
(-), multiplied (*), or divided (/). The percent sign (%)
shows the remainder when the two values are divided and the
caret (^) shows the result when one of the two numbers is
used as an exponent of the other. 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 it.
lx The value in register x is pushed on the stack. The
register x is not altered. All registers start at zero.
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.
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dc(1)
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, removes it, and prints it.
f All values on the stack 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 it as a string of dc commands.
X Replaces the number on the top of the stack with its scale
factor.
[ ... ]
Puts the bracketed ASCII string onto the top of the stack.
<x >x =x
The top two elements of the stack are popped and compared.
Register x is evaluated if they obey the stated relation.
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 ignored.
! Interprets the rest of the line as a DG/UX system 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 the
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
will be reasonable if all are changed together.
z The stack level is pushed onto the stack.
Z Replaces the number on the top of the stack with its
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dc(1)
length.
? A line of input is taken from the input source (usually the
terminal) and executed.
; : Used by bc for array operations.
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EXAMPLES
$ cat dc.infile1
10sa2sb
lad+p
lalb/p
q
$ dc dc.infile1
20
5
$
In this example, the dc command uses dc.infile1 for its input,
and dc.outfile1 for its output. The first line of dc.infile1
causes the a and b registers to be loaded with the values 10 and
2, respectively. The next 2 lines use the a and b register
values to perform some arithmetic. The second line pushes the a
register on the stack, duplicates it and then adds the two
numbers together. The third line pushes the b register and the a
register on the stack and then divides b by a. In both cases the
result is pushed on the stack, and the p causes the result to be
printed to the output file. The 20 is the result of 10+10 and
the 5 is the result of 10/2.
$ dc
[3 5 * p]
x
15
^d
$
In this example, dc.infile2 is used for the input for dc, and
dc.outfile2 is used for the output. The first line of the input
pushes the strings of commands onto the stack. The x command
treats the top of the stack as a string of commands and executes
them. The p in the string of commands causes the result (15) to
be written to the output file.
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dc(1)
$ cat dc.infile3
[6 4 + p] sa
5
5
=a
q
$ dc dc.infile3
10
$
In this example, dc uses dc.infile3 for its input and dc.outfile3
for its output. The first line of the input causes register "a"
to be loaded with the given string of commands ([6 4 + p]). The
next 2 lines cause 2 5's to be pushed on the stack. The =a
command then checks the top 2 values on the stack to see if
they're equal. Since they are, the commands in the "a" register
are executed. The result (10) is written to the screen.
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SEE ALSO
bc(1).
DIAGNOSTICS
x is unimplemented X is an octal number.
stack empty Not enough elements on the stack to do what
was asked.
Out of space The free list is exhausted (too many digits).
Out of headers Too many numbers being kept around.
Out of pushdown Too many items on the stack.
Nesting Depth Too many levels of nested execution.
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