sbase/dc.1

.Dd January 14, 2026
.Dt DC 1
.Os sbase
.Sh NAME
.Nm dc
.Nd arbitrary-precision desk calculator
.Sh SYNOPSIS
.Nm
.Op Fl i
.Op Ar file ...
.Sh DESCRIPTION
.Nm
is a reverse-polish notation arbitrary-precision desk calculator.
It reads and executes commands from each
.Ar file
in sequence.
After processing all files,
.Nm
reads from stdin.
.Pp
Numbers are arbitrary-precision decimal values.
Numbers may contain a decimal point and use
.Ql _
as a negative sign prefix.
When the input base is greater than 10, letters A-F represent digits 10-15.
.Sh OPTIONS
.Bl -tag -width Ds
.It Fl i
Extended identifier mode.
Register names can be enclosed in
.Ql < Ns No ... Ns >
(numeric identifiers) or
.Ql \&" Ns No ... Ns \&"
(string identifiers).
.El
.Sh COMMANDS
.Ss Printing
.Bl -tag -width Ds
.It Ic p
Print the value on top of the stack with a newline,
without popping it.
.It Ic n
Print the value on top of the stack without a newline,
and pop it.
.It Ic P
Print the value on top of the stack as a byte stream.
For strings, print the characters directly.
For numbers, print it in base 100 representing the internal representation.
The value is popped.
.It Ic f
Print all values on the stack, one per line, from top to bottom.
.El
.Ss Arithmetic
.Bl -tag -width Ds
.It Ic +
Pop two values, add them, and push the result.
.It Ic \-
Pop two values, subtract the top from the second, and push the result.
.It Ic *
Pop two values, multiply them, and push the result.
.It Ic /
Pop two values, divide the second by the top, and push the quotient.
The scale of the result is determined by the
.Ic scale
parameter.
.It Ic %
Pop two values, compute the remainder of dividing the second by the top,
and push the result.
.It Ic ~
Pop two values, compute both quotient and remainder,
pushing the quotient first then the remainder on top.
.It Ic ^
Pop two values, raise the second to the power of the top, and push the result.
The exponent is truncated to an integer.
.It Ic v
Pop the top value, compute its square root, and push the result.
The precision is determined by the
.Ic scale
parameter.
.El
.Ss Stack
.Bl -tag -width Ds
.It Ic c
Clear the stack.
.It Ic d
Duplicate the top of the stack.
.It Ic r
Reverse the order of the top two values on the stack.
.It Ic z
Push the current stack depth.
.El
.Ss Registers
Registers are named storage locations.
In normal mode, register names are single characters.
With the
.Fl i
option, extended names are available.
Each register also has an associated stack.
.Bl -tag -width Ds
.It Ic s Ns Ar x
Pop the top value and store it in register
.Ar x .
.It Ic l Ns Ar x
Push a copy of the value in register
.Ar x
onto the stack.
.It Ic S Ns Ar x
Pop the top value and push it onto register
.Ar x Ns 's
stack.
.It Ic L Ns Ar x
Pop the top value from register
.Ar x Ns 's
stack and push it onto the main stack.
.El
.Ss Arrays
Each register has an associated array.
.Bl -tag -width Ds
.It Ic : Ns Ar x
Pop an index, then pop a value, and store the value at that index in array
.Ar x .
.It Ic ; Ns Ar x
Pop an index and push the value at that index in array
.Ar x .
.El
.Ss Parameters
.Bl -tag -width Ds
.It Ic i
Pop the top value and use it as the input radix.
The input base must be between 2 and 16.
.It Ic o
Pop the top value and use it as the output radix.
The output base must be at least 2.
.It Ic k
Pop the top value and use it as the scale
.Pq number of decimal places
for arithmetic operations.
The scale must be non-negative.
.It Ic I
Push the current input radix.
.It Ic O
Push the current output radix.
.It Ic K
Push the current scale.
.El
.Ss Strings and Macros
.Bl -tag -width Ds
.It Ic \&[ Ns Ar string Ns Ic \&]
Push
.Ar string
onto the stack.
Brackets inside the string must be balanced or escaped with a backslash.
.It Ic x
Pop the top value.
If it is a string, execute it as a macro.
If it is a number, push it back.
.El
.Ss Conditionals
The conditional commands pop two values, compare them,
and if the condition is true, execute the contents of register
.Ar x
as a macro.
.Bl -tag -width Ds
.It Ic > Ns Ar x
Execute register
.Ar x
if the second value is greater than the top.
.It Ic < Ns Ar x
Execute register
.Ar x
if the second value is less than the top.
.It Ic = Ns Ar x
Execute register
.Ar x
if the two values are equal.
.It Ic !> Ns Ar x
Execute register
.Ar x
if the second value is not greater than (less or equal to) the top.
.It Ic !< Ns Ar x
Execute register
.Ar x
if the second value is not less than (greater or equal to) the top.
.It Ic != Ns Ar x
Execute register
.Ar x
if the two values are not equal.
.El
.Ss Control
.Bl -tag -width Ds
.It Ic q
Quit.
If executing a macro, exit two macro levels.
.It Ic Q
Pop a value and quit that many macro levels.
.El
.Ss Input
.Bl -tag -width Ds
.It Ic ?
Read a line from stdin and execute it.
.It Ic #
Comment.
The rest of the line is ignored.
.It Ic !\& Ns Ar command
Execute
.Ar command
as a shell command.
.El
.Ss Number Information
.Bl -tag -width Ds
.It Ic Z
Pop a value and push its length.
For numbers, push the number of significant digits.
For strings, push the number of characters.
.It Ic X
Pop a value and push its scale (number of fractional digits).
For strings, push 0.
.El
.Sh EXAMPLES
Compute 6 * 7:
.Bd -literal -offset indent
6 7*p
.Ed
.Pp
Compute 2^10:
.Bd -literal -offset indent
2 10^p
.Ed
.Pp
Compute square root of 2 with 20 decimal places:
.Bd -literal -offset indent
20k 2vp
.Ed
.Pp
Factorial using recursion (store in register f):
.Bd -literal -offset indent
[d1-d1<f*]sf 10lf xp
.Ed
.Sh SEE ALSO
.Xr bc 1
.Rs
.%A R. H. Morris
.%A L. L. Cherry
.%T "DC \(em An Interactive Desk Calculator"
.Re
.Sh STANDARDS
.Nm
is compatible with traditional UNIX dc implementations.
The
.Fl i
flag,
.Ic #
comments and
the
.Ic ~
operator
are extensions to the traditional dc specification.