NAME

bc − arbitrary-precision arithmetic language

SYNOPSIS

bc [ −c ] [ −l ] [ file ... ]

DESCRIPTION

bc is an interactive processor for a language that resembles C but provides unlimited precision arithmetic.  It takes input from any files given, then reads the standard input.  The bc(1) utility is actually a preprocessor for dc(1), which it invokes automatically unless the −c option is present.  In this case the dc input is sent to the standard output instead.  The options are as follows:

−c Compile only. The output is send to the standard output. 

−l Argument stands for the name of an arbitrary precision math library. 

The syntax for bc programs is as follows; L means letter a−z, E means expression, S means statement. 

Comments
are enclosed in /∗ and ∗/. 

Names
simple variables: L
array elements: L [ E ]
The words “ibase”, “obase”, and “scale”

Other operands
arbitrarily long numbers with optional sign and decimal point.
( E )
sqrt ( E )
length ( E )number of significant decimal digits
scale ( E )number of digits right of decimal point
L ( E , ... , E )

Operators
+   −   ∗   /   %   ^    (% is remainder; ^ is power)
++   −−   (prefix and postfix; apply to names)
==   <=   >=   !=   <   >
=   =+   =−   =∗   =/ =%   =^

Statements
E
{ S ; ... ; S }
if ( E ) S
while ( E ) S
for ( E ; E ; E ) S
null statement
break
quit

Function definitions
define L ( L ,..., L ) {
auto L, ... , L
S; ... S
return ( E )
}

Functions in −l math library
s(x)sine
c(x)cosine
e(x)exponential
l(x)log
a(x)arctangent
j(n,x)Bessel function

All function arguments are passed by value. 

The value of a statement that is an expression is printed unless the main operator is an assignment.  Either semicolons or new-lines may separate statements.  Assignment to scale influences the number of digits to be retained on arithmetic operations in the manner of dc(1). Assignments to ibase or obase set the input and output number radix respectively. 

The same letter may be used as an array, a function, and a simple variable simultaneously.  All variables are global to the program.  “Auto” variables are pushed down during function calls.  When using arrays as function arguments or defining them as automatic variables, empty square brackets must follow the array name. 

EXAMPLE

scale = 20
define e(x){
auto a, b, c, i, s
a = 1
b = 1
s = 1
for(i=1; 1==1; i++){
a = a∗x
b = b∗i
c = a/b
if(c == 0) return(s)
s = s+c
}
}

defines a function to compute an approximate value of the exponential function and

for(i=1; i<=10; i++) e(i)

prints approximate values of the exponential function of the first ten integers. 

FILES

/usr/lib/lib.bmathematical library
/usr/bin/dcdesk calculator proper

SEE ALSO

dc(1). 

BUGS

The bc command does not yet recognize the logical operators, && and ││. 
For statement must have all three expressions (E’s). 
Quit is interpreted when read, not when executed. 

March 13, 1992