- desk calculator
dc is an arbitrary precision arithmetic package. 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 dc is a stacking (reverse Polish) calculator. If an argument is given, input is taken from that file until its end, then from the standard input.
bc is a preprocessor for dc that provides infix notation and a C-like syntax that implements functions. bc also provides reasonable control structures for programs. See bc(1).
The following constructions are recognized under both /usr/bin/dc and /usr/xpg6/bin/dc:
The value of the number is pushed on the stack. A number is an unbroken string of the digits 0-9. It may be preceded by an underscore (_) to input a negative number. Numbers may contain decimal points.
The top of the stack is popped and stored into a register named x, where x may be any character. If the s is capitalized, x is treated as a stack and the value is pushed on it.
The value in register x is pushed on the stack. The register x is not altered. All registers start with zero value. If the l is capitalized, register x is treated as a stack and its top value is popped onto the main stack.
The top value on the stack is duplicated.
The top value on the stack is printed. The top value remains unchanged.
Interprets the top of the stack as an ASCII string, removes it, and prints it.
All values on the stack are printed.
Exits the program. If executing a string, the recursion level is popped by two.
Exits the program. The top value on the stack is popped and the string execution level is popped by that value.
Treats the top element of the stack as a character string and executes it as a string of dc commands.
Replaces the number on the top of the stack with its scale factor.
Puts the bracketed ASCII string onto the top of the stack.
The top two elements of the stack are popped and compared. Register x is evaluated if they obey the stated relation.
Replaces the top element on the stack by its square root. Any existing fractional part of the argument is taken into account, but otherwise the scale factor is ignored.
Interprets the rest of the line as a shell command.
All values on the stack are popped.
The top value on the stack is popped and used as the number radix for further input.
Pushes the input base on the top of the stack.
The top value on the stack is popped and used as the number radix for further output.
Pushes the output base on the top of the stack.
The top of the stack is popped, and that value is used as a non-negative scale factor: the appropriate number of places are 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 changed together.
Pushes the current scale factor on the top of the stack.
The stack level is pushed onto the stack.
Replaces the number on the top of the stack with its length.
A line of input is taken from the input source (usually the terminal) and executed.
Displays dc debugging information.
Used by bc(1) for array operations.
The following construction is recognized under /usr/bin/dc, using the scale of whatever the result is.
The top two values on the stack are added (+), subtracted (-), multiplied (*), divided (/), remaindered (%), or exponentiated (^). 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.
The following construction is recognized under /usr/xpg6/bin/dc. The results of division are forced to be a scale of 20.
The top two values on the stack are added (+), subtracted (-), multiplied (*), divided (/), remaindered (%), or exponentiated (^). 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.
Ensures that the scale set prior to division is the scale of the result.
示例 1 Printing the first ten values of n!
This example prints the first ten values of n!:
[la1+dsa*pla10>y]sy 0sa1 lyx
See attributes(5) for descriptions of the following attributes:
x is an octal number.
The free list is exhausted (too many digits).
Too many pushes onto the stack (stack overflow).
Too many pops from the stack (stack underflow).
Too many levels of nested execution.
Division by zero.
Square root of a negative number is not defined (no imaginary numbers).
dc only processes integer exponentiation.
The largest exponent allowed is 999.
The input base x: 2<= x <= 16.
The input base x: 2<= x <= 16.
The output base must be no larger than BC_BASE_MAX.
Scale factor cannot be less than 1.
A scale factor cannot be larger than BC_SCALE_MAX.
Too many variables have been specified.
Index cannot be less than 1.
An index cannot be larger than BC_DIM_MAX.