1.\' 2.\' This file documents DC, an arbitrary precision calculator. 3.\' 4.\' Published by the Free Software Foundation, 675 Massachusetts Avenue, 5.\' Cambridge, MA 02139 USA 6.\' 7.\' Copyright (C) 1984 Free Software Foundation, Inc. 8.\' 9.\' Permission is granted to make and distribute verbatim copies of this 10.\' manual provided the copyright notice and this permission notice are 11.\' preserved on all copies. 12.\' 13.\' Permission is granted to copy and distribute modified versions of 14.\' this manual under the conditions for verbatim copying, provided that 15.\' the entire resulting derived work is distributed under the terms of a 16.\' permission notice identical to this one. 17.\' 18.\' Permission is granted to copy and distribute translations of this 19.\' manual into another language, under the above conditions for modified 20.\' versions, except that this permission notice may be stated in a 21.\' translation approved by the Foundation. 22.\' 23.Dd March 1, 1993 24.Dt DC 1 25.Os BSD 4 26.Sh NAME 27.Nm dc 28.Nd desk calculator 29.Sh SYNOPSIS 30.Nm dc 31.Sh DESCRIPTION 32DC is a reverse-polish desk calculator which supports unlimited 33precision arithmetic. It also allows you to define and call macros. 34Normally DC reads from the standard input; if any command arguments are 35given to it, they are filenames, and DC reads and executes the contents 36of the files before reading from standard input. All output is to 37standard output. 38.Pp 39To exit, use `q'. `C-c' does not exit; it is used to abort macros 40that are looping, etc. (Currently this is not true; `C-c' does exit.) 41.Pp 42A reverse-polish calculator stores numbers on a stack. Entering a 43number pushes it on the stack. Arithmetic operations pop arguments off 44the stack and push the results. 45.Pp 46To enter a number in DC, type the digits, with an optional decimal 47point. Exponential notation is not supported. To enter a negative 48number, begin the number with `_'. `-' cannot be used for this, as it 49is a binary operator for subtraction instead. To enter two numbers in 50succession, separate them with spaces or newlines. These have no 51meaning as commands. 52.Sh Printing Commands 53.Bl -tag -width Ds 54`p' 55 Prints the value on the top of the stack, without altering the 56 stack. A newline is printed after the value. 57 58`P' 59 Prints the value on the top of the stack, popping it off, and does 60 not print a newline after. 61 62`f' 63 Prints the entire contents of the stack and the contents of all of 64 the registers, without altering anything. This is a good command 65 to use if you are lost or want to figure out what the effect of 66 some command has been. 67.El 68.Sh Arithmetic 69.Bl -tag -width Ds 70`+' 71 Pops two values off the stack, adds them, and pushes the result. 72 The precision of the result is determined only by the values of 73 the arguments, and is enough to be exact. 74 75`-' 76 Pops two values, subtracts the first one popped from the second 77 one popped, and pushes the result. 78 79`*' 80 Pops two values, multiplies them, and pushes the result. The 81 number of fraction digits in the result is controlled by the 82 current precision flag (see below) and does not depend on the 83 values being multiplied. 84 85`/' 86 Pops two values, divides the second one popped from the first one 87 popped, and pushes the result. The number of fraction digits is 88 specified by the precision flag. 89 90`%' 91 Pops two values, computes the remainder of the division that the 92 `/' command would do, and pushes that. The division is done with 93 as many fraction digits as the precision flag specifies, and the 94 remainder is also computed with that many fraction digits. 95 96`^' 97 Pops two values and exponentiates, using the first value popped as 98 the exponent and the second popped as the base. The fraction part 99 of the exponent is ignored. The precision flag specifies the 100 number of fraction digits in the result. 101 102`v' 103 Pops one value, computes its square root, and pushes that. The 104 precision flag specifies the number of fraction digits in the 105 result. 106.El 107.Pp 108Most arithmetic operations are affected by the "precision flag", 109which you can set with the `k' command. The default precision value is 110zero, which means that all arithmetic except for addition and 111subtraction produces integer results. 112.Pp 113The remainder operation (`%') requires some explanation: applied to 114arguments `a' and `b' it produces `a - (b * (a / b))', where `a / b' is 115computed in the current precision. 116.Sh Stack Control 117.Bl -tag -width Ds 118`c' 119 Clears the stack, rendering it empty. 120 121`d' 122 Duplicates the value on the top of the stack, pushing another copy 123 of it. Thus, `4d*p' computes 4 squared and prints it. 124 125.El 126.Sh Registers 127.Pp 128DC provides 128 memory registers, each named by a single ASCII 129character. You can store a number in a register and retrieve it later. 130.Pp 131.Bl -tag -width Ds 132`sR' 133 Pop the value off the top of the stack and store it into register 134 R. 135 136`lR' 137 Copy the value in register R, and push it onto the stack. This 138 does not alter the contents of R. 139 140 Each register also contains its own stack. The current register 141 value is the top of the register's stack. 142 143`SR' 144 Pop the value off the top of the (main) stack and push it onto the 145 stack of register R. The previous value of the register becomes 146 inaccessible. 147 148`LR' 149 Pop the value off the top of register R's stack and push it onto 150 the main stack. The previous value in register R's stack, if any, 151 is now accessible via the `lR' command. 152.El 153.Pp 154The `f' command prints a list of all registers that have contents 155stored in them, together with their contents. Only the current 156contents of each register (the top of its stack) is printed. 157.Sh Parameters 158.Pp 159DC has three parameters that control its operation: the precision, 160the input radix, and the output radix. The precision specifies the 161number of fraction digits to keep in the result of most arithmetic 162operations. The input radix controls the interpretation of numbers 163typed in; *all* numbers typed in use this radix. The output radix is 164used for printing numbers. 165.Pp 166The input and output radices are separate parameters; you can make 167them unequal, which can be useful or confusing. Each radix must be 168between 2 and 36 inclusive. The precision must be zero or greater. 169The precision is always measured in decimal digits, regardless of the 170current input or output radix. 171.Pp 172.Bl -tag -width Ds 173`i' 174 Pops the value off the top of the stack and uses it to set the 175 input radix. 176 177`o' 178`k' 179 Similarly set the output radix and the precision. 180 181`I' 182 Pushes the current input radix on the stack. 183 184`O' 185`K' 186 Similarly push the current output radix and the current precision. 187.El 188.Sh Strings 189.Pp 190DC can operate on strings as well as on numbers. The only things you 191can do with strings are print them and execute them as macros (which 192means that the contents of the string are processed as DC commands). 193Both registers and the stack can hold strings, and DC always knows 194whether any given object is a string or a number. Some commands such as 195arithmetic operations demand numbers as arguments and print errors if 196given strings. Other commands can accept either a number or a string; 197for example, the `p' command can accept either and prints the object 198according to its type. 199.Bl -tag -width Ds 200`[CHARACTERS]' 201 Makes a string containing CHARACTERS and pushes it on the stack. 202 For example, `[foo]P' prints the characters `foo' (with no 203 newline). 204 205`x' 206 Pops a value off the stack and executes it as a macro. Normally 207 it should be a string; if it is a number, it is simply pushed back 208 onto the stack. For example, `[1p]x' executes the macro `1p', 209 which pushes 1 on the stack and prints `1' on a separate line. 210 211 Macros are most often stored in registers; `[1p]sa' stores a macro 212 to print `1' into register `a', and `lax' invokes the macro. 213 214`>R' 215 Pops two values off the stack and compares them assuming they are 216 numbers, executing the contents of register R as a macro if the 217 original top-of-stack is greater. Thus, `1 2>a' will invoke 218 register `a''s contents and `2 1>a' will not. 219 220`<R' 221 Similar but invokes the macro if the original top-of-stack is less. 222 223`=R' 224 Similar but invokes the macro if the two numbers popped are equal. 225 This can also be validly used to compare two strings for equality. 226 227`?' 228 Reads a line from the terminal and executes it. This command 229 allows a macro to request input from the user. 230 231`q' 232 During the execution of a macro, this comand does not exit DC. 233 Instead, it exits from that macro and also from the macro which 234 invoked it (if any). 235 236`Q' 237 Pops a value off the stack and uses it as a count of levels of 238 macro execution to be exited. Thus, `3Q' exits three levels. 239.El 240.Sh Status Inquiry 241.Bl -tag -width Ds 242`Z' 243 Pops a value off the stack, calculates the number of digits it has 244 (or number of characters, if it is a string) and pushes that 245 number. 246 247`X' 248 Pops a value off the stack, calculates the number of fraction 249 digits it has, and pushes that number. For a string, the value 250 pushed is -1. 251 252`z' 253 Pushes the current stack depth; the number of objects on the stack 254 before the execution of the `z' command. 255 256`I' 257 Pushes the current value of the input radix. 258 259`O' 260 Pushes the current value of the output radix. 261 262`K' 263 Pushes the current value of the precision. 264.El 265.Sh Bugs 266.Pp 267The `:' and `;' commands of the Unix DC program are not supported, 268as the documentation does not say what they do. The `!' command is not 269supported, but will be supported as soon as a library for executing a 270line as a command exists. 271.Sh SEE ALSO 272.Xr bc 1 273