rand.3

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th RAND III 1/15/73
.sh NAME
rand, srand \*- random number generator
.sh SYNOPSIS
(seed in r0)
.br
.ft B
jsr	pc,srand	/to initialize
.s3
jsr	pc,rand	/to get a random number
.s3
.nf
srand(seed)
int seed;
.s3
rand( )
.fi
.ft R
.s3
.sh DESCRIPTION
.it Rand
uses a multiplicative congruential
random number generator to return successive pseudo-random
numbers (in r0) in the range from 0 to 2\u\s715\s10\d\*-1.
.s3
The generator is reinitialized by calling
.it srand
with 1 as argument (in r0).
It can be set to a random starting point by calling
.it srand
with whatever you like as argument,
for example the low-order word
of the time.
.sh BUGS
The low-order bits are not very random.