.TH DC 1.SH NAMEdc \- desk calculator.SH SYNOPSIS.B dc[.I file].SH DESCRIPTION.I Dcis an arbitrary precision desk calculator.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.I dcisa 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:.TPnumberThe value of the number is pushed on the stack.A number is an unbroken string of the digits .B 0-9A-F or.BR 0-9a-f .A hexadecimal number beginning with a lower caseletter must be preceded by a zero to distinguish itfrom the command associated with the letter.It may be preceded by an underscore.B _to input anegative number.Numbers may contain decimal points..TP.L+  - /  *  %  ^Add.LR + ,subtract.LR - ,multiply.LR * ,divide.LR / ,remainder.LR % ,or exponentiate.L ^the top two values on the stack.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..TP.BI s x.br.ns.TP.BI S xPop the top of the stack and store intoa register named.IR x ,where.I xmay be any character.Under operation.B Sregister.I xis treated as a stack and the value is pushed on it..TP.BI l x.br.ns.TP.BI L xPush the value in register.I xonto the stack.The register.I xis not altered.All registers start with zero value.Under operation.B Lregister.I xis treated as a stack and its top value is popped onto the main stack..TP.B  dDuplicate thetop value on the stack..TP.B  pPrint the top value on the stack.The top value remains unchanged..B Pinterprets the top of the stack as antextstring,removes it, and prints it..TP.B  fPrint the values on the stack..TP.B  q.br.ns.TP.B QExit the program.If executing a string, the recursion level ispopped by two.Under operation.B Qthe top value on the stack is popped and the string execution level is poppedby that value..TP.B  xTreat the top element of the stack as a character stringand execute it as a string of.I dccommands..TP.B  XReplace the number on the top of the stack with its scale factor..TP.B "[ ... ]"Put the bracketedtextstring on the top of the stack..TP.PD0.BI < x.TP.BI > x.TP.BI = x.PDPop and compare thetop two elements of the stack.Register.I xis executed if they obey the statedrelation..TP.B  vReplace the top element on the stack by its square root.Any existing fractional part of the argument is takeninto account, but otherwise the scale factor is ignored..TP.B  !Interpret the rest of the line as a shell command..TP.B  cClear the stack..TP.B  iThe top value on the stack is popped and used as thenumber base for further input..TP.B IPush the input base on the top of the stack..TP.B  oThe top value on the stack is popped and used as thenumber base for further output.In bases larger than 10, each `digit' prints as a group of decimal digits..TP.B OPush the output base on the top of the stack..TP.B  kPop the top of the stack, and use that value asa non-negative scale factor:the appropriate number of placesare 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 changedtogether..TP.B  zPush the stack level onto the stack..TP.B  ZReplace the number on the top of the stack with its length..TP.B  ?A line of input is taken from the input source (usually the terminal)and executed..TP.B "; :"Used by .I bcfor array operations..PPThe scale factor set by.B kdetermines how many digits are kept to the right ofthe decimal point.If.I sis the current scale factor,.I sais the scale of the first operand,.I sbis the scale of the second,and.I bis the (integer) second operand,results are truncated to the following scales..IP.nf\fL+\fR,\fL-\fR	max(\fIsa,sb\fR)\fL*\fR	min(\fIsa\fR+\fIsb \fR, max\fR(\fIs,sa,sb\fR))\fL/\fI	s\fL%\fR	so that dividend = divisor*quotient + remainder; remainder has sign of dividend\fL^\fR	min(\fIsa\fR\(mu|\fIb\fR|, max(\fIs,sa\fR))\fLv\fR	max(\fIs,sa\fR).fi.SH EXAMPLES.LPPrint the first ten values of.IR n !.IP.EX[la1+dsa*pla10>y]sy0sa1lyx.EE.SH SOURCE.B /sys/src/cmd/dc.c.SH "SEE ALSO".IR bc (1),.IR hoc (1).SH DIAGNOSTICS.I x.LR "is unimplemented" ,where.I xis an octal number: an internal error..br`Out of headers'for too many numbers being kept around..br`Nesting depth'for too many levels of nested execution..SH BUGSWhen the input base exceeds 16,there is no notation for digits greater than.BR F ..PPPast its time.