# FreeBSD Man Pages

home | helpDC(1) DC(1)NAMEdc, An Arbitrary Precision CalculatorSYNOPSISdcDESCRIPTIONDC is a reverse-polish desk calculator which supports unlimited preci- sion arithmetic. It also allows you to define and call macros. Nor- mally DC reads from the standard input; if any command arguments are given to it, they are filenames, and DC reads and executes the contents of the files before reading from standard input. All output is to standard output. A reverse-polish calculator stores numbers on a stack. Entering a num- ber pushes it on the stack. Arithmetic operations pop arguments off the stack and push the results. To enter a number in DC, type the digits, with an optional decimal point. Exponential notation is not supported. To enter a negative number, begin the number with `_'. `-' cannot be used for this, as it is a binary operator for subtraction instead. To enter two numbers in succession, separate them with spaces or newlines. These have no mean- ing as commands.Printing CommandspPrints the value on the top of the stack, without altering the stack. A newline is printed after the value.PPrints the value on the top of the stack, popping it off, and does not print a newline after.fPrints the entire contents of the stack and the contents of all of the registers, without altering anything. This is a good command to use if you are lost or want to figure out what the effect of some com- mand has been.Arithmetic+Pops two values off the stack, adds them, and pushes the result. The precision of the result is determined only by the values of the argu- ments, and is enough to be exact.-Pops two values, subtracts the first one popped from the second one popped, and pushes the result.*Pops two values, multiplies them, and pushes the result. The number of fraction digits in the result is controlled by the current precision flag (see below) and does not depend on the values being multiplied./Pops two values, divides the second one popped from the first one popped, and pushes the result. The number of fraction digits is speci- fied by the precision flag.%Pops two values, computes the remainder of the division that the/command would do, and pushes that. The division is done with as many fraction digits as the precision flag specifies, and the remainder is also computed with that many fraction digits.^Pops two values and exponentiates, using the first value popped as the exponent and the second popped as the base. The fraction part of the exponent is ignored. The precision flag specifies the number of fraction digits in the result.vPops one value, computes its square root, and pushes that. The pre- cision flag specifies the number of fraction digits in the result. Most arithmetic operations are affected by the "precision flag", which you can set with thekcommand. The default precision value is zero, which means that all arithmetic except for addition and subtraction produces integer results. The remainder operation%requires some explanation: applied to argu- ments `a' and `b' it produces `a - (b * (a / b))', where `a / b' is computed in the current precision.Stack ControlcClears the stack, rendering it empty.dDuplicates the value on the top of the stack, pushing another copy of it. Thus, `4d*p' computes 4 squared and prints it.RegistersDC provides 128 memory registers, each named by a single ASCII charac- ter. You can store a number in a register and retrieve it later.srPop the value off the top of the stack and store it into registerr.lrCopy the value in registerrand push it onto the stack. This does not alter the contents ofr. Each register also contains its own stack. The current register value is the top of the register's stack.SrPop the value off the top of the (main) stack and push it onto the stack of registerr. The previous value of the register becomes inac- cessible.LrPop the value off the top of registerr's stack and push it onto the main stack. The previous value in registerr's stack, if any, is now accessible via theIrcommand. Thefcommand prints a list of all registers that have contents stored in them, together with their contents. Only the current contents of each register (the top of its stack) is printed.ParametersDC has three parameters that control its operation: the precision, the input radix, and the output radix. The precision specifies the number of fraction digits to keep in the result of most arithmetic operations. The input radix controls the interpretation of numbers typed in; all- numbers typed in use this radix. The output radix is used for printing numbers. The input and output radices are separate parameters; you can make them unequal, which can be useful or confusing. Each radix must be between 2 and 36 inclusive. The precision must be zero or greater. The preci- sion is always measured in decimal digits, regardless of the current input or output radix.iPops the value off the top of the stack and uses it to set the input radix.okSimilarly set the output radix and the precision.IPushes the current input radix on the stack.OKSimilarly push the current output radix and the current precision.StringsDC can operate on strings as well as on numbers. The only things you can do with strings are print them and execute them as macros (which means that the contents of the string are processed as DC commands). Both registers and the stack can hold strings, and DC always knows whether any given object is a string or a number. Some commands such as arithmetic operations demand numbers as arguments and print errors if given strings. Other commands can accept either a number or a string; for example, thepcommand can accept either and prints the object according to its type.[characters]Makes a string containingcharactersand pushes it on the stack. For example,[foo]pprints the charactersfoo(with no new- line).xPops a value off the stack and executes it as a macro. Normally it should be a string; if it is a number, it is simply pushed back onto the stack. For example,[1p]xexecutes the macro1pwhich pushes1on the stack and prints1on a separate line. Macros are most often stored in registers;[1p]sastores a macro to print1into registera, andlaxinvokes the macro. >rPops two values off the stack and compares them assuming they are numbers, executing the contents of registerras a macro if the origi- nal top-of-stack is greater. Thus,12>awill invoke registera's con- tents and21>awill not. <rSimilar but invokes the macro if the original top-of-stack is less.=rSimilar but invokes the macro if the two numbers popped are equal. This can also be validly used to compare two strings for equality.?Reads a line from the terminal and executes it. This command allows a macro to request input from the user.qDuring the execution of a macro, this comand does not exit DC. Instead, it exits from that macro and also from the macro which invoked it (if any).QPops a value off the stack and uses it as a count of levels of macro execution to be exited. Thus,3Qexits three levels.Status InquiryZPops a value off the stack, calculates the number of digits it has (or number of characters, if it is a string) and pushes that number.XPops a value off the stack, calculates the number of fraction digits it has, and pushes that number. For a string, the value pushed is -1.zPushes the current stack depth; the number of objects on the stack before the execution of thezcommand.IPushes the current value of the input radix.OPushes the current value of the output radix.KPushes the current value of the precision.NotesThe:and;commands of the Unix DC program are not supported, as the documentation does not say what they do. The!command is not sup- ported, but will be supported as soon as a library for executing a line as a command exists.BUGSEmail bug reports tobug-gnu-utils@prep.ai.mit.edu. Be sure to include the word ``dc'' somewhere in the ``Subject:'' field. GNU Project 03 Aug 1993 DC(1)

NAME | SYNOPSIS | DESCRIPTION | Printing Commands | Arithmetic | Stack Control | Registers | Parameters | Strings | Status Inquiry | Notes | BUGS

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