ic.1

操作系统设计与实现源码

.TH IC 1
.SH NAME
ic \- integer calculator
.SH SYNOPSIS
\fBic\fR [\fIexpression\fR]\fR
.br
.de FL
.TP
\\fB\\$1\\fR
\\$2
..
.de EX
.TP 20
\\fB\\$1\\fR
# \\$2
..
.SH EXAMPLES
.EX "ic    " "Start the calculator"
.EX "ic 250 300+" "Start calculator with 550 on the stack"
.SH DESCRIPTION
.PP
\fIIc\fR is a simple RPN (Reverse Polish Notation)
calculator, used for small calculations
and base conversions. All calculations are done using 32 bit
integers.
The standard input is usually a keyboard and the standard output 
requires a device with a \&'termcap\&' entry.
The program starts by interpreting any <args> as commands, where
the separation between arguments is considered to be the same as
the ENTER key. For example, 
.PP
.B "	""ic 692 784+"
.PP
After reading the arguments input is from the keyboard.
.SS "Stack Operations"
.PP
The operation of this program is similar to an RPN calculator.
A six level stack is used. The ENTER key pushes the stack up one 
level. For example, \&'12+5\&' is entered as \&'12 ENTER 5 +".
.PP
The top two entries on the stack are exchanged by the \fIx\fR 
command, and the stack is rolled down one (popped) by the
\fIp\fR key.
The top of the stack may be cleared by pressing the back-space
key. The whole stack and the registers are initialized by a \fIz\fR.
.SS "Numeric Entry"
.PP
The input and output bases are initially decimal, but they may
be changed using the \fIi\fR and \fIo\fR commands. The \fIi\fR command changes
both bases, but the \fIo\fR command changes just the output base.
These commands take a one character argument of \fIh\fR, \fId\fR, \fIo\fR or
\fIb\fR to change to Hexadecimal, Decimal, Octal or Binary. While the 
input base is hexadecimal the letters \fIa\fR through \fIf\fR are used 
to represent the decimal values 10 through 15.
.PP
When the input base is decimal: multiply, divide and remainder
are signed, otherwise they are performed unsigned.
.PP
The output base may also be changed to ASCII (\fIa\fR), this causes
the least significant 7 bits of a value to be displayed as a
character. To input an ASCII value the translate (\fIt\fR) command
may be used, it accepts one character as its argument.
.SS "Calculations"
.PP
The arithmetic operations supported are: Negate (\&'.\&'), 
Add (\&'+\&'), Subtract (\&'\(mi\&'), Multiply (\&'*\&'), 
Divide (\&'/\&'), and Remainder (\&'%\&').
The logical (Boolean) operations available are: NOT (\&'~\&'), 
AND (\&'&\&'), OR (\&'|\&'), 
and EXCLUSIVE-OR (\&'^\&').
.PP
After one of these operations the last top of stack value is
saved. It may be restored by pressing \fIl\fR (L).
.SS "Saving Results"
.PP
Ten temporary registers are available. The Store (\fIs\fR) command
followed by a digit (\&'0\&'..\&'9\&') will copy the top of the stack
to the specified register. The Recall (\fIr\fR) command pushes the
contents of a register onto the top of the stack.
.PP
If the Store command is followed by a \&'+\&' preceding the digit, then
the top of the stack will be added to the specified \&'accumulator\&'
register.
.PP
Values may also be written to a file. The \fIw\fR command writes the
top of the stack, using the current output base, to a file called 
\&'pad\&' in the current directory.  If the user does not have write 
access to the current directory then the file \fI/tmp/pad_$USER\fR is 
used as the scratch pad. The scratch pad file is erased on the
first use of the \fIw\fR command within each new invocation of \&'ic\&'.
.SS "Miscellaneous"
.PP
The Quit (\fIq\fR) key causes an immediate exit. 
The \fIm\fR command temporarily leaves \fIic\fR 
by invoking the shell as a sub-process.
For help while using \fIic\fR, hit the \fIh\fR key. If an erroneous key
is pressed the bell will sound.
.SS "Command Summary"
.PP
Note that many commands have an alternative key-code available
on the extended AT keyboard. This aids entry by including most
commands on the right side of the keyboard.
.ta 0.25i 1.5i
.nf
.PP
	ENTER	Enter (push up)
	BS (DEL)	Clear top of stack
	h	Help
	i	Input base  (h, d, o, b)
	l  (PGDN)	Last top of stack
	m	\s-2MINIX\s0 shell
	o	Output base (h, d, o, b, a)
	p  (DOWN)	Pop stack (roll down)
	q  (END)	Quit
	r  (LEFT)	Recall (0-9)
	s  (RIGHT)	Store [+] (0-9)
	t	Translate (char)
	w  (PGUP)	Write top of stack to scratch pad
	x  (UP)	Exchange top of stack
	z  (HOME)	Zero all state
	.	Change sign
	+  (+)	Add
	-  (-)	Subtract
	*	Multiply
	/	Divide
	%  (sh/5)	Remainder
	(tilde)	Not
	&	And
	|	Or
	^	Exclusive-or
.fi
.SS "Author"
.PP
\fIIc\fR was written by Terrence W. Holm.