```
```

NAME

```     drand48,  erand48,  lrand48,  nrand48,   mrand48,   jrand48,
srand48,  seed48,  lcong48  - generate uniformly distributed
pseudo-random numbers

```

SYNOPSIS

```     #include <stdlib.h>

double drand48(void);

double erand48(unsigned short int xsubi[3]);

long int lrand48(void);

long int nrand48(unsigned short int xsubi[3]);

long int mrand48(void);

long int jrand48(unsigned short int xsubi[3]);

void srand48(long int seedval));

unsigned short int *seed48(unsignedshortint seed16v [3]);

void lcong48(unsigned short int param[7]);

```

DESCRIPTION

```     These functions generate  pseudo-random  numbers  using  the
linear congruential algorithm and 48-bit integer arithmetic.

The drand48() and erand48()  functions  return  non-negative
double-precision floating-point values uniformly distributed
between [0.0, 1.0).

The lrand48() and nrand48()  functions  return  non-negative
long integers uniformly distributed between 0 and 2^31.

The mrand48() and jrand48()  functions  return  signed  long
integers uniformly distributed between -2^31 and 2^31.

The srand48(), seed48() and lcong48() functions are initial-
ization  functions,  one  of  which  should be called before
using drand48(),  lrand48()  or  mrand49().   The  functions
erand48(),  nrand48()  and  jrand48() do not require an ini-
tialization function to be called first.

All the functions work by generating a  sequence  of  48-bit
integers, Xi, according to the linear congruential formula:

Xn+1 = (aXn + c) mod

The parameter m = 2^48, hence 48-bit integer  arithmetic  is
performed.   Unless  lcong48()  is called, a and c are given
by:

a = 0x5DEECE66D
c = 0xB

The value  returned  by  any  of  the  functions  drand48(),
erand48(),  lrand48(),  nrand48(), mrand48() or jrand48() is
computed by first generating  the  next  48-bit  Xi  in  the
sequence.  Then the appropriate number of bits, according to
the type of data item to be returned,  is  copied  from  the
high-order  bits  of  Xi  and  transformed into the returned
value.

The functions drand48(), lrand48() and mrand48()  store  the
last  48-bit  Xi generated in an internal buffer.  The func-
tions erand48(), nrand48() and jrand48() require the calling
program  to  provide storage for the successive Xi values in
the array argument xsubi.  The functions are initialized  by
placing  the  initial value of Xi into the array before cal-
ling the function for the first time.

The initializer function srand48() sets the high  order  32-
bits  of  Xi to the argument seedval.  The low order 16-bits
are set to the arbitrary value 0x330E.

The initializer function seed48() sets the value  of  Xi  to
the  48-bit  value  specified in the array argument seed16v.
The previous value of Xi is copied into an  internal  buffer
and a pointer to this buffer is returned by seed48().

The initialization function lcong48()  allows  the  user  to
specify initial values for Xi, a and c.  Array argument ele-
ments param[0-2]  specify  Xi,  param[3-5]  specify  a,  and
param[6]  specifies  c.   After lcong48() has been called, a
subsequent call to either srand48() or seed48() will restore
the standard values of a and c.

```

CONFORMING TO

```     SVID 3

```

NOTES

```     These functions are  declared  obsolete  by  SVID  3,  which
states that rand(3) should be used instead.

```

```     rand(3), random(3)