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FACTOR(VI)  −  PWB/UNIX 1/15/73

NAME

factor − discover prime factors of a number

SYNOPSIS

factor [ number ]

DESCRIPTION

When factor is invoked without an argument, it waits for a number to be typed in.  If you type in a positive number less than 256 (about 7.2×1016) it will factor the number and print its prime factors; each one is printed the proper number of times. Then it waits for another number. It exits if it encounters a zero or any non-numeric character. If factor is invoked with an argument, it factors the number as above and then exits.  Maximum time to factor is proportional to √n
‾
and occurs when n is prime or the square of a prime.  It takes 1 minute to factor a prime near 1013. 

DIAGNOSTICS

‘Ouch.’ for input out of range or for garbage input. 

BUGS

Typewritten Software • bear@typewritten.org • Edmonds, WA 98026