vendor/bc/3.1.1

1 files changed, 1387 insertions, 0 deletions

diff --git a/manuals/dc/HN.1 b/manuals/dc/HN.1
new file mode 100644
index 000000000000..cb97ca4cafb3
--- /dev/null
+++ b/manuals/dc/HN.1
@@ -0,0 +1,1387 @@
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.\" Copyright (c) 2018-2020 Gavin D. Howard and contributors.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions are met:
+.\"
+.\" * Redistributions of source code must retain the above copyright notice,
+.\"   this list of conditions and the following disclaimer.
+.\"
+.\" * Redistributions in binary form must reproduce the above copyright notice,
+.\"   this list of conditions and the following disclaimer in the documentation
+.\"   and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+.\" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+.\" POSSIBILITY OF SUCH DAMAGE.
+.\"
+.TH "DC" "1" "July 2020" "Gavin D. Howard" "General Commands Manual"
+.SH Name
+.PP
+dc \- arbitrary\-precision reverse\-Polish notation calculator
+.SH SYNOPSIS
+.PP
+\f[B]dc\f[] [\f[B]\-hiPvVx\f[]] [\f[B]\-\-version\f[]]
+[\f[B]\-\-help\f[]] [\f[B]\-\-interactive\f[]] [\f[B]\-\-no\-prompt\f[]]
+[\f[B]\-\-extended\-register\f[]] [\f[B]\-e\f[] \f[I]expr\f[]]
+[\f[B]\-\-expression\f[]=\f[I]expr\f[]...] [\f[B]\-f\f[]
+\f[I]file\f[]...] [\f[B]\-file\f[]=\f[I]file\f[]...] [\f[I]file\f[]...]
+.SH DESCRIPTION
+.PP
+dc(1) is an arbitrary\-precision calculator.
+It uses a stack (reverse Polish notation) to store numbers and results
+of computations.
+Arithmetic operations pop arguments off of the stack and push the
+results.
+.PP
+If no files are given on the command\-line as extra arguments (i.e., not
+as \f[B]\-f\f[] or \f[B]\-\-file\f[] arguments), then dc(1) reads from
+\f[B]stdin\f[].
+Otherwise, those files are processed, and dc(1) will then exit.
+.PP
+This is different from the dc(1) on OpenBSD and possibly other dc(1)
+implementations, where \f[B]\-e\f[] (\f[B]\-\-expression\f[]) and
+\f[B]\-f\f[] (\f[B]\-\-file\f[]) arguments cause dc(1) to execute them
+and exit.
+The reason for this is that this dc(1) allows users to set arguments in
+the environment variable \f[B]DC_ENV_ARGS\f[] (see the \f[B]ENVIRONMENT
+VARIABLES\f[] section).
+Any expressions given on the command\-line should be used to set up a
+standard environment.
+For example, if a user wants the \f[B]scale\f[] always set to
+\f[B]10\f[], they can set \f[B]DC_ENV_ARGS\f[] to \f[B]\-e 10k\f[], and
+this dc(1) will always start with a \f[B]scale\f[] of \f[B]10\f[].
+.PP
+If users want to have dc(1) exit after processing all input from
+\f[B]\-e\f[] and \f[B]\-f\f[] arguments (and their equivalents), then
+they can just simply add \f[B]\-e q\f[] as the last command\-line
+argument or define the environment variable \f[B]DC_EXPR_EXIT\f[].
+.SH OPTIONS
+.PP
+The following are the options that dc(1) accepts.
+.TP
+.B \f[B]\-h\f[], \f[B]\-\-help\f[]
+Prints a usage message and quits.
+.RS
+.RE
+.TP
+.B \f[B]\-v\f[], \f[B]\-V\f[], \f[B]\-\-version\f[]
+Print the version information (copyright header) and exit.
+.RS
+.RE
+.TP
+.B \f[B]\-i\f[], \f[B]\-\-interactive\f[]
+Forces interactive mode.
+(See the \f[B]INTERACTIVE MODE\f[] section.)
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]\-P\f[], \f[B]\-\-no\-prompt\f[]
+Disables the prompt in TTY mode.
+(The prompt is only enabled in TTY mode.
+See the \f[B]TTY MODE\f[] section) This is mostly for those users that
+do not want a prompt or are not used to having them in dc(1).
+Most of those users would want to put this option in
+\f[B]DC_ENV_ARGS\f[].
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]\-x\f[] \f[B]\-\-extended\-register\f[]
+Enables extended register mode.
+See the \f[I]Extended Register Mode\f[] subsection of the
+\f[B]REGISTERS\f[] section for more information.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]\-e\f[] \f[I]expr\f[], \f[B]\-\-expression\f[]=\f[I]expr\f[]
+Evaluates \f[I]expr\f[].
+If multiple expressions are given, they are evaluated in order.
+If files are given as well (see below), the expressions and files are
+evaluated in the order given.
+This means that if a file is given before an expression, the file is
+read in and evaluated first.
+.RS
+.PP
+In other dc(1) implementations, this option causes the program to
+execute the expressions and then exit.
+This dc(1) does not, unless the \f[B]DC_EXPR_EXIT\f[] is defined (see
+the \f[B]ENVIRONMENT VARIABLES\f[] section).
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]\-f\f[] \f[I]file\f[], \f[B]\-\-file\f[]=\f[I]file\f[]
+Reads in \f[I]file\f[] and evaluates it, line by line, as though it were
+read through \f[B]stdin\f[].
+If expressions are also given (see above), the expressions are evaluated
+in the order given.
+.RS
+.PP
+In other dc(1) implementations, this option causes the program to
+execute the files and then exit.
+This dc(1) does not, unless the \f[B]DC_EXPR_EXIT\f[] is defined (see
+the \f[B]ENVIRONMENT VARIABLES\f[] section).
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.PP
+All long options are \f[B]non\-portable extensions\f[].
+.SH STDOUT
+.PP
+Any non\-error output is written to \f[B]stdout\f[].
+.PP
+\f[B]Note\f[]: Unlike other dc(1) implementations, this dc(1) will issue
+a fatal error (see the \f[B]EXIT STATUS\f[] section) if it cannot write
+to \f[B]stdout\f[], so if \f[B]stdout\f[] is closed, as in \f[B]dc
+>&\-\f[], it will quit with an error.
+This is done so that dc(1) can report problems when \f[B]stdout\f[] is
+redirected to a file.
+.PP
+If there are scripts that depend on the behavior of other dc(1)
+implementations, it is recommended that those scripts be changed to
+redirect \f[B]stdout\f[] to \f[B]/dev/null\f[].
+.SH STDERR
+.PP
+Any error output is written to \f[B]stderr\f[].
+.PP
+\f[B]Note\f[]: Unlike other dc(1) implementations, this dc(1) will issue
+a fatal error (see the \f[B]EXIT STATUS\f[] section) if it cannot write
+to \f[B]stderr\f[], so if \f[B]stderr\f[] is closed, as in \f[B]dc
+2>&\-\f[], it will quit with an error.
+This is done so that dc(1) can exit with an error code when
+\f[B]stderr\f[] is redirected to a file.
+.PP
+If there are scripts that depend on the behavior of other dc(1)
+implementations, it is recommended that those scripts be changed to
+redirect \f[B]stderr\f[] to \f[B]/dev/null\f[].
+.SH SYNTAX
+.PP
+Each item in the input source code, either a number (see the
+\f[B]NUMBERS\f[] section) or a command (see the \f[B]COMMANDS\f[]
+section), is processed and executed, in order.
+Input is processed immediately when entered.
+.PP
+\f[B]ibase\f[] is a register (see the \f[B]REGISTERS\f[] section) that
+determines how to interpret constant numbers.
+It is the "input" base, or the number base used for interpreting input
+numbers.
+\f[B]ibase\f[] is initially \f[B]10\f[].
+The max allowable value for \f[B]ibase\f[] is \f[B]16\f[].
+The min allowable value for \f[B]ibase\f[] is \f[B]2\f[].
+The max allowable value for \f[B]ibase\f[] can be queried in dc(1)
+programs with the \f[B]T\f[] command.
+.PP
+\f[B]obase\f[] is a register (see the \f[B]REGISTERS\f[] section) that
+determines how to output results.
+It is the "output" base, or the number base used for outputting numbers.
+\f[B]obase\f[] is initially \f[B]10\f[].
+The max allowable value for \f[B]obase\f[] is \f[B]DC_BASE_MAX\f[] and
+can be queried with the \f[B]U\f[] command.
+The min allowable value for \f[B]obase\f[] is \f[B]0\f[].
+If \f[B]obase\f[] is \f[B]0\f[], values are output in scientific
+notation, and if \f[B]obase\f[] is \f[B]1\f[], values are output in
+engineering notation.
+Otherwise, values are output in the specified base.
+.PP
+Outputting in scientific and engineering notations are
+\f[B]non\-portable extensions\f[].
+.PP
+The \f[I]scale\f[] of an expression is the number of digits in the
+result of the expression right of the decimal point, and \f[B]scale\f[]
+is a register (see the \f[B]REGISTERS\f[] section) that sets the
+precision of any operations (with exceptions).
+\f[B]scale\f[] is initially \f[B]0\f[].
+\f[B]scale\f[] cannot be negative.
+The max allowable value for \f[B]scale\f[] can be queried in dc(1)
+programs with the \f[B]V\f[] command.
+.PP
+\f[B]seed\f[] is a register containing the current seed for the
+pseudo\-random number generator.
+If the current value of \f[B]seed\f[] is queried and stored, then if it
+is assigned to \f[B]seed\f[] later, the pseudo\-random number generator
+is guaranteed to produce the same sequence of pseudo\-random numbers
+that were generated after the value of \f[B]seed\f[] was first queried.
+.PP
+Multiple values assigned to \f[B]seed\f[] can produce the same sequence
+of pseudo\-random numbers.
+Likewise, when a value is assigned to \f[B]seed\f[], it is not
+guaranteed that querying \f[B]seed\f[] immediately after will return the
+same value.
+In addition, the value of \f[B]seed\f[] will change after any call to
+the \f[B]\[aq]\f[] command or the \f[B]"\f[] command that does not get
+receive a value of \f[B]0\f[] or \f[B]1\f[].
+The maximum integer returned by the \f[B]\[aq]\f[] command can be
+queried with the \f[B]W\f[] command.
+.PP
+\f[B]Note\f[]: The values returned by the pseudo\-random number
+generator with the \f[B]\[aq]\f[] and \f[B]"\f[] commands are guaranteed
+to \f[B]NOT\f[] be cryptographically secure.
+This is a consequence of using a seeded pseudo\-random number generator.
+However, they \f[B]are\f[] guaranteed to be reproducible with identical
+\f[B]seed\f[] values.
+.PP
+The pseudo\-random number generator, \f[B]seed\f[], and all associated
+operations are \f[B]non\-portable extensions\f[].
+.SS Comments
+.PP
+Comments go from \f[B]#\f[] until, and not including, the next newline.
+This is a \f[B]non\-portable extension\f[].
+.SH NUMBERS
+.PP
+Numbers are strings made up of digits, uppercase letters up to
+\f[B]F\f[], and at most \f[B]1\f[] period for a radix.
+Numbers can have up to \f[B]DC_NUM_MAX\f[] digits.
+Uppercase letters are equal to \f[B]9\f[] + their position in the
+alphabet (i.e., \f[B]A\f[] equals \f[B]10\f[], or \f[B]9+1\f[]).
+If a digit or letter makes no sense with the current value of
+\f[B]ibase\f[], they are set to the value of the highest valid digit in
+\f[B]ibase\f[].
+.PP
+Single\-character numbers (i.e., \f[B]A\f[] alone) take the value that
+they would have if they were valid digits, regardless of the value of
+\f[B]ibase\f[].
+This means that \f[B]A\f[] alone always equals decimal \f[B]10\f[] and
+\f[B]F\f[] alone always equals decimal \f[B]15\f[].
+.PP
+In addition, dc(1) accepts numbers in scientific notation.
+These have the form \f[B]<number>e<integer>\f[].
+The power (the portion after the \f[B]e\f[]) must be an integer.
+An example is \f[B]1.89237e9\f[], which is equal to \f[B]1892370000\f[].
+Negative exponents are also allowed, so \f[B]4.2890e_3\f[] is equal to
+\f[B]0.0042890\f[].
+.PP
+\f[B]WARNING\f[]: Both the number and the exponent in scientific
+notation are interpreted according to the current \f[B]ibase\f[], but
+the number is still multiplied by \f[B]10^exponent\f[] regardless of the
+current \f[B]ibase\f[].
+For example, if \f[B]ibase\f[] is \f[B]16\f[] and dc(1) is given the
+number string \f[B]FFeA\f[], the resulting decimal number will be
+\f[B]2550000000000\f[], and if dc(1) is given the number string
+\f[B]10e_4\f[], the resulting decimal number will be \f[B]0.0016\f[].
+.PP
+Accepting input as scientific notation is a \f[B]non\-portable
+extension\f[].
+.SH COMMANDS
+.PP
+The valid commands are listed below.
+.SS Printing
+.PP
+These commands are used for printing.
+.PP
+Note that both scientific notation and engineering notation are
+available for printing numbers.
+Scientific notation is activated by assigning \f[B]0\f[] to
+\f[B]obase\f[] using \f[B]0o\f[], and engineering notation is activated
+by assigning \f[B]1\f[] to \f[B]obase\f[] using \f[B]1o\f[].
+To deactivate them, just assign a different value to \f[B]obase\f[].
+.PP
+Printing numbers in scientific notation and/or engineering notation is a
+\f[B]non\-portable extension\f[].
+.TP
+.B \f[B]p\f[]
+Prints the value on top of the stack, whether number or string, and
+prints a newline after.
+.RS
+.PP
+This does not alter the stack.
+.RE
+.TP
+.B \f[B]n\f[]
+Prints the value on top of the stack, whether number or string, and pops
+it off of the stack.
+.RS
+.RE
+.TP
+.B \f[B]P\f[]
+Pops a value off the stack.
+.RS
+.PP
+If the value is a number, it is truncated and the absolute value of the
+result is printed as though \f[B]obase\f[] is \f[B]UCHAR_MAX+1\f[] and
+each digit is interpreted as an ASCII character, making it a byte
+stream.
+.PP
+If the value is a string, it is printed without a trailing newline.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]f\f[]
+Prints the entire contents of the stack, in order from newest to oldest,
+without altering anything.
+.RS
+.PP
+Users should use this command when they get lost.
+.RE
+.SS Arithmetic
+.PP
+These are the commands used for arithmetic.
+.TP
+.B \f[B]+\f[]
+The top two values are popped off the stack, added, and the result is
+pushed onto the stack.
+The \f[I]scale\f[] of the result is equal to the max \f[I]scale\f[] of
+both operands.
+.RS
+.RE
+.TP
+.B \f[B]\-\f[]
+The top two values are popped off the stack, subtracted, and the result
+is pushed onto the stack.
+The \f[I]scale\f[] of the result is equal to the max \f[I]scale\f[] of
+both operands.
+.RS
+.RE
+.TP
+.B \f[B]*\f[]
+The top two values are popped off the stack, multiplied, and the result
+is pushed onto the stack.
+If \f[B]a\f[] is the \f[I]scale\f[] of the first expression and
+\f[B]b\f[] is the \f[I]scale\f[] of the second expression, the
+\f[I]scale\f[] of the result is equal to
+\f[B]min(a+b,max(scale,a,b))\f[] where \f[B]min()\f[] and \f[B]max()\f[]
+return the obvious values.
+.RS
+.RE
+.TP
+.B \f[B]/\f[]
+The top two values are popped off the stack, divided, and the result is
+pushed onto the stack.
+The \f[I]scale\f[] of the result is equal to \f[B]scale\f[].
+.RS
+.PP
+The first value popped off of the stack must be non\-zero.
+.RE
+.TP
+.B \f[B]%\f[]
+The top two values are popped off the stack, remaindered, and the result
+is pushed onto the stack.
+.RS
+.PP
+Remaindering is equivalent to 1) Computing \f[B]a/b\f[] to current
+\f[B]scale\f[], and 2) Using the result of step 1 to calculate
+\f[B]a\-(a/b)*b\f[] to \f[I]scale\f[]
+\f[B]max(scale+scale(b),scale(a))\f[].
+.PP
+The first value popped off of the stack must be non\-zero.
+.RE
+.TP
+.B \f[B]~\f[]
+The top two values are popped off the stack, divided and remaindered,
+and the results (divided first, remainder second) are pushed onto the
+stack.
+This is equivalent to \f[B]x y / x y %\f[] except that \f[B]x\f[] and
+\f[B]y\f[] are only evaluated once.
+.RS
+.PP
+The first value popped off of the stack must be non\-zero.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]^\f[]
+The top two values are popped off the stack, the second is raised to the
+power of the first, and the result is pushed onto the stack.
+.RS
+.PP
+The first value popped off of the stack must be an integer, and if that
+value is negative, the second value popped off of the stack must be
+non\-zero.
+.RE
+.TP
+.B \f[B]v\f[]
+The top value is popped off the stack, its square root is computed, and
+the result is pushed onto the stack.
+The \f[I]scale\f[] of the result is equal to \f[B]scale\f[].
+.RS
+.PP
+The value popped off of the stack must be non\-negative.
+.RE
+.TP
+.B \f[B]_\f[]
+If this command \f[I]immediately\f[] precedes a number (i.e., no spaces
+or other commands), then that number is input as a negative number.
+.RS
+.PP
+Otherwise, the top value on the stack is popped and copied, and the copy
+is negated and pushed onto the stack.
+This behavior without a number is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]b\f[]
+The top value is popped off the stack, and if it is zero, it is pushed
+back onto the stack.
+Otherwise, its absolute value is pushed onto the stack.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]|\f[]
+The top three values are popped off the stack, a modular exponentiation
+is computed, and the result is pushed onto the stack.
+.RS
+.PP
+The first value popped is used as the reduction modulus and must be an
+integer and non\-zero.
+The second value popped is used as the exponent and must be an integer
+and non\-negative.
+The third value popped is the base and must be an integer.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]$\f[]
+The top value is popped off the stack and copied, and the copy is
+truncated and pushed onto the stack.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]\@\f[]
+The top two values are popped off the stack, and the precision of the
+second is set to the value of the first, whether by truncation or
+extension.
+.RS
+.PP
+The first value popped off of the stack must be an integer and
+non\-negative.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]H\f[]
+The top two values are popped off the stack, and the second is shifted
+left (radix shifted right) to the value of the first.
+.RS
+.PP
+The first value popped off of the stack must be an integer and
+non\-negative.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]h\f[]
+The top two values are popped off the stack, and the second is shifted
+right (radix shifted left) to the value of the first.
+.RS
+.PP
+The first value popped off of the stack must be an integer and
+non\-negative.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]G\f[]
+The top two values are popped off of the stack, they are compared, and a
+\f[B]1\f[] is pushed if they are equal, or \f[B]0\f[] otherwise.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]N\f[]
+The top value is popped off of the stack, and if it a \f[B]0\f[], a
+\f[B]1\f[] is pushed; otherwise, a \f[B]0\f[] is pushed.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B](\f[]
+The top two values are popped off of the stack, they are compared, and a
+\f[B]1\f[] is pushed if the first is less than the second, or \f[B]0\f[]
+otherwise.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]{\f[]
+The top two values are popped off of the stack, they are compared, and a
+\f[B]1\f[] is pushed if the first is less than or equal to the second,
+or \f[B]0\f[] otherwise.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B])\f[]
+The top two values are popped off of the stack, they are compared, and a
+\f[B]1\f[] is pushed if the first is greater than the second, or
+\f[B]0\f[] otherwise.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]}\f[]
+The top two values are popped off of the stack, they are compared, and a
+\f[B]1\f[] is pushed if the first is greater than or equal to the
+second, or \f[B]0\f[] otherwise.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]M\f[]
+The top two values are popped off of the stack.
+If they are both non\-zero, a \f[B]1\f[] is pushed onto the stack.
+If either of them is zero, or both of them are, then a \f[B]0\f[] is
+pushed onto the stack.
+.RS
+.PP
+This is like the \f[B]&&\f[] operator in bc(1), and it is \f[I]not\f[] a
+short\-circuit operator.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]m\f[]
+The top two values are popped off of the stack.
+If at least one of them is non\-zero, a \f[B]1\f[] is pushed onto the
+stack.
+If both of them are zero, then a \f[B]0\f[] is pushed onto the stack.
+.RS
+.PP
+This is like the \f[B]||\f[] operator in bc(1), and it is \f[I]not\f[] a
+short\-circuit operator.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.SS Pseudo\-Random Number Generator
+.PP
+dc(1) has a built\-in pseudo\-random number generator.
+These commands query the pseudo\-random number generator.
+(See Parameters for more information about the \f[B]seed\f[] value that
+controls the pseudo\-random number generator.)
+.PP
+The pseudo\-random number generator is guaranteed to \f[B]NOT\f[] be
+cryptographically secure.
+.TP
+.B \f[B]\[aq]\f[]
+Generates an integer between 0 and \f[B]DC_RAND_MAX\f[], inclusive (see
+the \f[B]LIMITS\f[] section).
+.RS
+.PP
+The generated integer is made as unbiased as possible, subject to the
+limitations of the pseudo\-random number generator.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]"\f[]
+Pops a value off of the stack, which is used as an \f[B]exclusive\f[]
+upper bound on the integer that will be generated.
+If the bound is negative or is a non\-integer, an error is raised, and
+dc(1) resets (see the \f[B]RESET\f[] section) while \f[B]seed\f[]
+remains unchanged.
+If the bound is larger than \f[B]DC_RAND_MAX\f[], the higher bound is
+honored by generating several pseudo\-random integers, multiplying them
+by appropriate powers of \f[B]DC_RAND_MAX+1\f[], and adding them
+together.
+Thus, the size of integer that can be generated with this command is
+unbounded.
+Using this command will change the value of \f[B]seed\f[], unless the
+operand is \f[B]0\f[] or \f[B]1\f[].
+In that case, \f[B]0\f[] is pushed onto the stack, and \f[B]seed\f[] is
+\f[I]not\f[] changed.
+.RS
+.PP
+The generated integer is made as unbiased as possible, subject to the
+limitations of the pseudo\-random number generator.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.SS Stack Control
+.PP
+These commands control the stack.
+.TP
+.B \f[B]c\f[]
+Removes all items from ("clears") the stack.
+.RS
+.RE
+.TP
+.B \f[B]d\f[]
+Copies the item on top of the stack ("duplicates") and pushes the copy
+onto the stack.
+.RS
+.RE
+.TP
+.B \f[B]r\f[]
+Swaps ("reverses") the two top items on the stack.
+.RS
+.RE
+.TP
+.B \f[B]R\f[]
+Pops ("removes") the top value from the stack.
+.RS
+.RE
+.SS Register Control
+.PP
+These commands control registers (see the \f[B]REGISTERS\f[] section).
+.TP
+.B \f[B]s\f[]\f[I]r\f[]
+Pops the value off the top of the stack and stores it into register
+\f[I]r\f[].
+.RS
+.RE
+.TP
+.B \f[B]l\f[]\f[I]r\f[]
+Copies the value in register \f[I]r\f[] and pushes it onto the stack.
+This does not alter the contents of \f[I]r\f[].
+.RS
+.RE
+.TP
+.B \f[B]S\f[]\f[I]r\f[]
+Pops the value off the top of the (main) stack and pushes it onto the
+stack of register \f[I]r\f[].
+The previous value of the register becomes inaccessible.
+.RS
+.RE
+.TP
+.B \f[B]L\f[]\f[I]r\f[]
+Pops the value off the top of the stack for register \f[I]r\f[] and push
+it onto the main stack.
+The previous value in the stack for register \f[I]r\f[], if any, is now
+accessible via the \f[B]l\f[]\f[I]r\f[] command.
+.RS
+.RE
+.SS Parameters
+.PP
+These commands control the values of \f[B]ibase\f[], \f[B]obase\f[],
+\f[B]scale\f[], and \f[B]seed\f[].
+Also see the \f[B]SYNTAX\f[] section.
+.TP
+.B \f[B]i\f[]
+Pops the value off of the top of the stack and uses it to set
+\f[B]ibase\f[], which must be between \f[B]2\f[] and \f[B]16\f[],
+inclusive.
+.RS
+.PP
+If the value on top of the stack has any \f[I]scale\f[], the
+\f[I]scale\f[] is ignored.
+.RE
+.TP
+.B \f[B]o\f[]
+Pops the value off of the top of the stack and uses it to set
+\f[B]obase\f[], which must be between \f[B]0\f[] and
+\f[B]DC_BASE_MAX\f[], inclusive (see the \f[B]LIMITS\f[] section and the
+\f[B]NUMBERS\f[] section).
+.RS
+.PP
+If the value on top of the stack has any \f[I]scale\f[], the
+\f[I]scale\f[] is ignored.
+.RE
+.TP
+.B \f[B]k\f[]
+Pops the value off of the top of the stack and uses it to set
+\f[B]scale\f[], which must be non\-negative.
+.RS
+.PP
+If the value on top of the stack has any \f[I]scale\f[], the
+\f[I]scale\f[] is ignored.
+.RE
+.TP
+.B \f[B]j\f[]
+Pops the value off of the top of the stack and uses it to set
+\f[B]seed\f[].
+The meaning of \f[B]seed\f[] is dependent on the current pseudo\-random
+number generator but is guaranteed to not change except for new major
+versions.
+.RS
+.PP
+The \f[I]scale\f[] and sign of the value may be significant.
+.PP
+If a previously used \f[B]seed\f[] value is used again, the
+pseudo\-random number generator is guaranteed to produce the same
+sequence of pseudo\-random numbers as it did when the \f[B]seed\f[]
+value was previously used.
+.PP
+The exact value assigned to \f[B]seed\f[] is not guaranteed to be
+returned if the \f[B]J\f[] command is used.
+However, if \f[B]seed\f[] \f[I]does\f[] return a different value, both
+values, when assigned to \f[B]seed\f[], are guaranteed to produce the
+same sequence of pseudo\-random numbers.
+This means that certain values assigned to \f[B]seed\f[] will not
+produce unique sequences of pseudo\-random numbers.
+.PP
+There is no limit to the length (number of significant decimal digits)
+or \f[I]scale\f[] of the value that can be assigned to \f[B]seed\f[].
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]I\f[]
+Pushes the current value of \f[B]ibase\f[] onto the main stack.
+.RS
+.RE
+.TP
+.B \f[B]O\f[]
+Pushes the current value of \f[B]obase\f[] onto the main stack.
+.RS
+.RE
+.TP
+.B \f[B]K\f[]
+Pushes the current value of \f[B]scale\f[] onto the main stack.
+.RS
+.RE
+.TP
+.B \f[B]J\f[]
+Pushes the current value of \f[B]seed\f[] onto the main stack.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]T\f[]
+Pushes the maximum allowable value of \f[B]ibase\f[] onto the main
+stack.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]U\f[]
+Pushes the maximum allowable value of \f[B]obase\f[] onto the main
+stack.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]V\f[]
+Pushes the maximum allowable value of \f[B]scale\f[] onto the main
+stack.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]W\f[]
+Pushes the maximum (inclusive) integer that can be generated with the
+\f[B]\[aq]\f[] pseudo\-random number generator command.
+.RS
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.SS Strings
+.PP
+The following commands control strings.
+.PP
+dc(1) can work with both numbers and strings, and registers (see the
+\f[B]REGISTERS\f[] section) can hold both strings and numbers.
+dc(1) always knows whether the contents of a register are a string or a
+number.
+.PP
+While arithmetic operations have to have numbers, and will print an
+error if given a string, other commands accept strings.
+.PP
+Strings can also be executed as macros.
+For example, if the string \f[B][1pR]\f[] is executed as a macro, then
+the code \f[B]1pR\f[] is executed, meaning that the \f[B]1\f[] will be
+printed with a newline after and then popped from the stack.
+.TP
+.B \f[B][\f[]\f[I]characters\f[]\f[B]]\f[]
+Makes a string containing \f[I]characters\f[] and pushes it onto the
+stack.
+.RS
+.PP
+If there are brackets (\f[B][\f[] and \f[B]]\f[]) in the string, then
+they must be balanced.
+Unbalanced brackets can be escaped using a backslash (\f[B]\\\f[])
+character.
+.PP
+If there is a backslash character in the string, the character after it
+(even another backslash) is put into the string verbatim, but the
+(first) backslash is not.
+.RE
+.TP
+.B \f[B]a\f[]
+The value on top of the stack is popped.
+.RS
+.PP
+If it is a number, it is truncated and its absolute value is taken.
+The result mod \f[B]UCHAR_MAX+1\f[] is calculated.
+If that result is \f[B]0\f[], push an empty string; otherwise, push a
+one\-character string where the character is the result of the mod
+interpreted as an ASCII character.
+.PP
+If it is a string, then a new string is made.
+If the original string is empty, the new string is empty.
+If it is not, then the first character of the original string is used to
+create the new string as a one\-character string.
+The new string is then pushed onto the stack.
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]x\f[]
+Pops a value off of the top of the stack.
+.RS
+.PP
+If it is a number, it is pushed back onto the stack.
+.PP
+If it is a string, it is executed as a macro.
+.PP
+This behavior is the norm whenever a macro is executed, whether by this
+command or by the conditional execution commands below.
+.RE
+.TP
+.B \f[B]>\f[]\f[I]r\f[]
+Pops two values off of the stack that must be numbers and compares them.
+If the first value is greater than the second, then the contents of
+register \f[I]r\f[] are executed.
+.RS
+.PP
+For example, \f[B]0 1>a\f[] will execute the contents of register
+\f[B]a\f[], and \f[B]1 0>a\f[] will not.
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.RE
+.TP
+.B \f[B]>\f[]\f[I]r\f[]\f[B]e\f[]\f[I]s\f[]
+Like the above, but will execute register \f[I]s\f[] if the comparison
+fails.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]!>\f[]\f[I]r\f[]
+Pops two values off of the stack that must be numbers and compares them.
+If the first value is not greater than the second (less than or equal
+to), then the contents of register \f[I]r\f[] are executed.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.RE
+.TP
+.B \f[B]!>\f[]\f[I]r\f[]\f[B]e\f[]\f[I]s\f[]
+Like the above, but will execute register \f[I]s\f[] if the comparison
+fails.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]<\f[]\f[I]r\f[]
+Pops two values off of the stack that must be numbers and compares them.
+If the first value is less than the second, then the contents of
+register \f[I]r\f[] are executed.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.RE
+.TP
+.B \f[B]<\f[]\f[I]r\f[]\f[B]e\f[]\f[I]s\f[]
+Like the above, but will execute register \f[I]s\f[] if the comparison
+fails.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]!<\f[]\f[I]r\f[]
+Pops two values off of the stack that must be numbers and compares them.
+If the first value is not less than the second (greater than or equal
+to), then the contents of register \f[I]r\f[] are executed.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.RE
+.TP
+.B \f[B]!<\f[]\f[I]r\f[]\f[B]e\f[]\f[I]s\f[]
+Like the above, but will execute register \f[I]s\f[] if the comparison
+fails.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]=\f[]\f[I]r\f[]
+Pops two values off of the stack that must be numbers and compares them.
+If the first value is equal to the second, then the contents of register
+\f[I]r\f[] are executed.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.RE
+.TP
+.B \f[B]=\f[]\f[I]r\f[]\f[B]e\f[]\f[I]s\f[]
+Like the above, but will execute register \f[I]s\f[] if the comparison
+fails.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]!=\f[]\f[I]r\f[]
+Pops two values off of the stack that must be numbers and compares them.
+If the first value is not equal to the second, then the contents of
+register \f[I]r\f[] are executed.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.RE
+.TP
+.B \f[B]!=\f[]\f[I]r\f[]\f[B]e\f[]\f[I]s\f[]
+Like the above, but will execute register \f[I]s\f[] if the comparison
+fails.
+.RS
+.PP
+If either or both of the values are not numbers, dc(1) will raise an
+error and reset (see the \f[B]RESET\f[] section).
+.PP
+This is a \f[B]non\-portable extension\f[].
+.RE
+.TP
+.B \f[B]?\f[]
+Reads a line from the \f[B]stdin\f[] and executes it.
+This is to allow macros to request input from users.
+.RS
+.RE
+.TP
+.B \f[B]q\f[]
+During execution of a macro, this exits the execution of that macro and
+the execution of the macro that executed it.
+If there are no macros, or only one macro executing, dc(1) exits.
+.RS
+.RE
+.TP
+.B \f[B]Q\f[]
+Pops a value from the stack which must be non\-negative and is used the
+number of macro executions to pop off of the execution stack.
+If the number of levels to pop is greater than the number of executing
+macros, dc(1) exits.
+.RS
+.RE
+.SS Status
+.PP
+These commands query status of the stack or its top value.
+.TP
+.B \f[B]Z\f[]
+Pops a value off of the stack.
+.RS
+.PP
+If it is a number, calculates the number of significant decimal digits
+it has and pushes the result.
+.PP
+If it is a string, pushes the number of characters the string has.
+.RE
+.TP
+.B \f[B]X\f[]
+Pops a value off of the stack.
+.RS
+.PP
+If it is a number, pushes the \f[I]scale\f[] of the value onto the
+stack.
+.PP
+If it is a string, pushes \f[B]0\f[].
+.RE
+.TP
+.B \f[B]z\f[]
+Pushes the current stack depth (before execution of this command).
+.RS
+.RE
+.SS Arrays
+.PP
+These commands manipulate arrays.
+.TP
+.B \f[B]:\f[]\f[I]r\f[]
+Pops the top two values off of the stack.
+The second value will be stored in the array \f[I]r\f[] (see the
+\f[B]REGISTERS\f[] section), indexed by the first value.
+.RS
+.RE
+.TP
+.B \f[B];\f[]\f[I]r\f[]
+Pops the value on top of the stack and uses it as an index into the
+array \f[I]r\f[].
+The selected value is then pushed onto the stack.
+.RS
+.RE
+.SH REGISTERS
+.PP
+Registers are names that can store strings, numbers, and arrays.
+(Number/string registers do not interfere with array registers.)
+.PP
+Each register is also its own stack, so the current register value is
+the top of the stack for the register.
+All registers, when first referenced, have one value (\f[B]0\f[]) in
+their stack.
+.PP
+In non\-extended register mode, a register name is just the single
+character that follows any command that needs a register name.
+The only exception is a newline (\f[B]\[aq]\\n\[aq]\f[]); it is a parse
+error for a newline to be used as a register name.
+.SS Extended Register Mode
+.PP
+Unlike most other dc(1) implentations, this dc(1) provides nearly
+unlimited amounts of registers, if extended register mode is enabled.
+.PP
+If extended register mode is enabled (\f[B]\-x\f[] or
+\f[B]\-\-extended\-register\f[] command\-line arguments are given), then
+normal single character registers are used \f[I]unless\f[] the character
+immediately following a command that needs a register name is a space
+(according to \f[B]isspace()\f[]) and not a newline
+(\f[B]\[aq]\\n\[aq]\f[]).
+.PP
+In that case, the register name is found according to the regex
+\f[B][a\-z][a\-z0\-9_]*\f[] (like bc(1) identifiers), and it is a parse
+error if the next non\-space characters do not match that regex.
+.SH RESET
+.PP
+When dc(1) encounters an error or a signal that it has a non\-default
+handler for, it resets.
+This means that several things happen.
+.PP
+First, any macros that are executing are stopped and popped off the
+stack.
+The behavior is not unlike that of exceptions in programming languages.
+Then the execution point is set so that any code waiting to execute
+(after all macros returned) is skipped.
+.PP
+Thus, when dc(1) resets, it skips any remaining code waiting to be
+executed.
+Then, if it is interactive mode, and the error was not a fatal error
+(see the \f[B]EXIT STATUS\f[] section), it asks for more input;
+otherwise, it exits with the appropriate return code.
+.SH PERFORMANCE
+.PP
+Most dc(1) implementations use \f[B]char\f[] types to calculate the
+value of \f[B]1\f[] decimal digit at a time, but that can be slow.
+This dc(1) does something different.
+.PP
+It uses large integers to calculate more than \f[B]1\f[] decimal digit
+at a time.
+If built in a environment where \f[B]DC_LONG_BIT\f[] (see the
+\f[B]LIMITS\f[] section) is \f[B]64\f[], then each integer has
+\f[B]9\f[] decimal digits.
+If built in an environment where \f[B]DC_LONG_BIT\f[] is \f[B]32\f[]
+then each integer has \f[B]4\f[] decimal digits.
+This value (the number of decimal digits per large integer) is called
+\f[B]DC_BASE_DIGS\f[].
+.PP
+In addition, this dc(1) uses an even larger integer for overflow
+checking.
+This integer type depends on the value of \f[B]DC_LONG_BIT\f[], but is
+always at least twice as large as the integer type used to store digits.
+.SH LIMITS
+.PP
+The following are the limits on dc(1):
+.TP
+.B \f[B]DC_LONG_BIT\f[]
+The number of bits in the \f[B]long\f[] type in the environment where
+dc(1) was built.
+This determines how many decimal digits can be stored in a single large
+integer (see the \f[B]PERFORMANCE\f[] section).
+.RS
+.RE
+.TP
+.B \f[B]DC_BASE_DIGS\f[]
+The number of decimal digits per large integer (see the
+\f[B]PERFORMANCE\f[] section).
+Depends on \f[B]DC_LONG_BIT\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_BASE_POW\f[]
+The max decimal number that each large integer can store (see
+\f[B]DC_BASE_DIGS\f[]) plus \f[B]1\f[].
+Depends on \f[B]DC_BASE_DIGS\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_OVERFLOW_MAX\f[]
+The max number that the overflow type (see the \f[B]PERFORMANCE\f[]
+section) can hold.
+Depends on \f[B]DC_LONG_BIT\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_BASE_MAX\f[]
+The maximum output base.
+Set at \f[B]DC_BASE_POW\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_DIM_MAX\f[]
+The maximum size of arrays.
+Set at \f[B]SIZE_MAX\-1\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_SCALE_MAX\f[]
+The maximum \f[B]scale\f[].
+Set at \f[B]DC_OVERFLOW_MAX\-1\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_STRING_MAX\f[]
+The maximum length of strings.
+Set at \f[B]DC_OVERFLOW_MAX\-1\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_NAME_MAX\f[]
+The maximum length of identifiers.
+Set at \f[B]DC_OVERFLOW_MAX\-1\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_NUM_MAX\f[]
+The maximum length of a number (in decimal digits), which includes
+digits after the decimal point.
+Set at \f[B]DC_OVERFLOW_MAX\-1\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_RAND_MAX\f[]
+The maximum integer (inclusive) returned by the \f[B]\[aq]\f[] command,
+if dc(1).
+Set at \f[B]2^DC_LONG_BIT\-1\f[].
+.RS
+.RE
+.TP
+.B Exponent
+The maximum allowable exponent (positive or negative).
+Set at \f[B]DC_OVERFLOW_MAX\f[].
+.RS
+.RE
+.TP
+.B Number of vars
+The maximum number of vars/arrays.
+Set at \f[B]SIZE_MAX\-1\f[].
+.RS
+.RE
+.PP
+These limits are meant to be effectively non\-existent; the limits are
+so large (at least on 64\-bit machines) that there should not be any
+point at which they become a problem.
+In fact, memory should be exhausted before these limits should be hit.
+.SH ENVIRONMENT VARIABLES
+.PP
+dc(1) recognizes the following environment variables:
+.TP
+.B \f[B]DC_ENV_ARGS\f[]
+This is another way to give command\-line arguments to dc(1).
+They should be in the same format as all other command\-line arguments.
+These are always processed first, so any files given in
+\f[B]DC_ENV_ARGS\f[] will be processed before arguments and files given
+on the command\-line.
+This gives the user the ability to set up "standard" options and files
+to be used at every invocation.
+The most useful thing for such files to contain would be useful
+functions that the user might want every time dc(1) runs.
+Another use would be to use the \f[B]\-e\f[] option to set
+\f[B]scale\f[] to a value other than \f[B]0\f[].
+.RS
+.PP
+The code that parses \f[B]DC_ENV_ARGS\f[] will correctly handle quoted
+arguments, but it does not understand escape sequences.
+For example, the string \f[B]"/home/gavin/some dc file.dc"\f[] will be
+correctly parsed, but the string \f[B]"/home/gavin/some "dc"
+file.dc"\f[] will include the backslashes.
+.PP
+The quote parsing will handle either kind of quotes, \f[B]\[aq]\f[] or
+\f[B]"\f[].
+Thus, if you have a file with any number of single quotes in the name,
+you can use double quotes as the outside quotes, as in \f[B]"some
+\[aq]bc\[aq] file.bc"\f[], and vice versa if you have a file with double
+quotes.
+However, handling a file with both kinds of quotes in
+\f[B]DC_ENV_ARGS\f[] is not supported due to the complexity of the
+parsing, though such files are still supported on the command\-line
+where the parsing is done by the shell.
+.RE
+.TP
+.B \f[B]DC_LINE_LENGTH\f[]
+If this environment variable exists and contains an integer that is
+greater than \f[B]1\f[] and is less than \f[B]UINT16_MAX\f[]
+(\f[B]2^16\-1\f[]), dc(1) will output lines to that length, including
+the backslash newline combo.
+The default line length is \f[B]70\f[].
+.RS
+.RE
+.TP
+.B \f[B]DC_EXPR_EXIT\f[]
+If this variable exists (no matter the contents), dc(1) will exit
+immediately after executing expressions and files given by the
+\f[B]\-e\f[] and/or \f[B]\-f\f[] command\-line options (and any
+equivalents).
+.RS
+.RE
+.SH EXIT STATUS
+.PP
+dc(1) returns the following exit statuses:
+.TP
+.B \f[B]0\f[]
+No error.
+.RS
+.RE
+.TP
+.B \f[B]1\f[]
+A math error occurred.
+This follows standard practice of using \f[B]1\f[] for expected errors,
+since math errors will happen in the process of normal execution.
+.RS
+.PP
+Math errors include divide by \f[B]0\f[], taking the square root of a
+negative number, using a negative number as a bound for the
+pseudo\-random number generator, attempting to convert a negative number
+to a hardware integer, overflow when converting a number to a hardware
+integer, and attempting to use a non\-integer where an integer is
+required.
+.PP
+Converting to a hardware integer happens for the second operand of the
+power (\f[B]^\f[]), places (\f[B]\@\f[]), left shift (\f[B]H\f[]), and
+right shift (\f[B]h\f[]) operators.
+.RE
+.TP
+.B \f[B]2\f[]
+A parse error occurred.
+.RS
+.PP
+Parse errors include unexpected \f[B]EOF\f[], using an invalid
+character, failing to find the end of a string or comment, and using a
+token where it is invalid.
+.RE
+.TP
+.B \f[B]3\f[]
+A runtime error occurred.
+.RS
+.PP
+Runtime errors include assigning an invalid number to \f[B]ibase\f[],
+\f[B]obase\f[], or \f[B]scale\f[]; give a bad expression to a
+\f[B]read()\f[] call, calling \f[B]read()\f[] inside of a
+\f[B]read()\f[] call, type errors, and attempting an operation when the
+stack has too few elements.
+.RE
+.TP
+.B \f[B]4\f[]
+A fatal error occurred.
+.RS
+.PP
+Fatal errors include memory allocation errors, I/O errors, failing to
+open files, attempting to use files that do not have only ASCII
+characters (dc(1) only accepts ASCII characters), attempting to open a
+directory as a file, and giving invalid command\-line options.
+.RE
+.PP
+The exit status \f[B]4\f[] is special; when a fatal error occurs, dc(1)
+always exits and returns \f[B]4\f[], no matter what mode dc(1) is in.
+.PP
+The other statuses will only be returned when dc(1) is not in
+interactive mode (see the \f[B]INTERACTIVE MODE\f[] section), since
+dc(1) resets its state (see the \f[B]RESET\f[] section) and accepts more
+input when one of those errors occurs in interactive mode.
+This is also the case when interactive mode is forced by the
+\f[B]\-i\f[] flag or \f[B]\-\-interactive\f[] option.
+.PP
+These exit statuses allow dc(1) to be used in shell scripting with error
+checking, and its normal behavior can be forced by using the
+\f[B]\-i\f[] flag or \f[B]\-\-interactive\f[] option.
+.SH INTERACTIVE MODE
+.PP
+Like bc(1), dc(1) has an interactive mode and a non\-interactive mode.
+Interactive mode is turned on automatically when both \f[B]stdin\f[] and
+\f[B]stdout\f[] are hooked to a terminal, but the \f[B]\-i\f[] flag and
+\f[B]\-\-interactive\f[] option can turn it on in other cases.
+.PP
+In interactive mode, dc(1) attempts to recover from errors (see the
+\f[B]RESET\f[] section), and in normal execution, flushes
+\f[B]stdout\f[] as soon as execution is done for the current input.
+.SH TTY MODE
+.PP
+If \f[B]stdin\f[], \f[B]stdout\f[], and \f[B]stderr\f[] are all
+connected to a TTY, dc(1) turns on "TTY mode."
+.PP
+The prompt is enabled in TTY mode.
+.PP
+TTY mode is different from interactive mode because interactive mode is
+required in the bc(1)
+specification (https://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html),
+and interactive mode requires only \f[B]stdin\f[] and \f[B]stdout\f[] to
+be connected to a terminal.
+.SH SIGNAL HANDLING
+.PP
+Sending a \f[B]SIGINT\f[] will cause dc(1) to stop execution of the
+current input.
+If dc(1) is in TTY mode (see the \f[B]TTY MODE\f[] section), it will
+reset (see the \f[B]RESET\f[] section).
+Otherwise, it will clean up and exit.
+.PP
+Note that "current input" can mean one of two things.
+If dc(1) is processing input from \f[B]stdin\f[] in TTY mode, it will
+ask for more input.
+If dc(1) is processing input from a file in TTY mode, it will stop
+processing the file and start processing the next file, if one exists,
+or ask for input from \f[B]stdin\f[] if no other file exists.
+.PP
+This means that if a \f[B]SIGINT\f[] is sent to dc(1) as it is executing
+a file, it can seem as though dc(1) did not respond to the signal since
+it will immediately start executing the next file.
+This is by design; most files that users execute when interacting with
+dc(1) have function definitions, which are quick to parse.
+If a file takes a long time to execute, there may be a bug in that file.
+The rest of the files could still be executed without problem, allowing
+the user to continue.
+.PP
+\f[B]SIGTERM\f[] and \f[B]SIGQUIT\f[] cause dc(1) to clean up and exit,
+and it uses the default handler for all other signals.
+.SH SEE ALSO
+.PP
+bc(1)
+.SH STANDARDS
+.PP
+The dc(1) utility operators are compliant with the operators in the
+bc(1) IEEE Std 1003.1\-2017
+(“POSIX.1\-2017”) (https://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html)
+specification.
+.SH BUGS
+.PP
+None are known.
+Report bugs at https://git.yzena.com/gavin/bc.
+.SH AUTHOR
+.PP
+Gavin D.
+Howard <yzena.tech@gmail.com> and contributors.