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Annotation of coherent/a/usr/man/ALL/rand, revision 1.1.1.1

1.1       root        1: 
                      2: 
                      3: rand()                   General Function                  rand()
                      4: 
                      5: 
                      6: 
                      7: 
                      8: Generate pseudo-random numbers
                      9: 
                     10: int rand()
                     11: 
                     12: rand generates  a set of  pseudo-random numbers.  It  returns in-
                     13: tegers in the range 0 to  32,767, and purportedly has a period of
                     14: 2^32.  rand will always  return the same series of random numbers
                     15: unless you  first call the function srand  to change rand's seed,
                     16: or beginning-point.
                     17: 
                     18: ***** Example *****
                     19: 
                     20: This example demonstrates  the functions rand and srand.  It uses
                     21: a threshold level  that is passed in argv[1] (default, MAXVAL/2),
                     22: the number  of trials passed  in argv[2] (default,  1,000), and a
                     23: seed passed in argv[3] (default, no seeding).
                     24: 
                     25: 
                     26: #define MAXVAL 32767    /* range of rand: [0,2^15-1] */
                     27: 
                     28: 
                     29: 
                     30: main(argc, argv)
                     31: int argc; char *argv[];
                     32: {
                     33:         register int i, hits, threshold, ntrials;
                     34: 
                     35: 
                     36: 
                     37:         hits = 0;
                     38:         threshold = (argc > 1) ? atoi(argv[1]) : MAXVAL/2;
                     39:         ntrials = (argc > 2) ? atoi(argv[2]) : 1000;
                     40:         if (argc > 3)
                     41:                 srand(atoi(argv[3]));
                     42: 
                     43: 
                     44: 
                     45:         for (i = 1; i <= ntrials; i++)
                     46:                 if (rand() > threshold)
                     47:                         ++hits;
                     48: 
                     49: 
                     50: 
                     51:         printf("%d values above %d in %d trials (%D%%).\n",
                     52:                 hits, threshold, ntrials, (100L*hits)/ntrials);
                     53: }
                     54: 
                     55: 
                     56: ***** See Also *****
                     57: 
                     58: general functions, srand()
                     59: _T_h_e _A_r_t _o_f _C_o_m_p_u_t_e_r _P_r_o_g_r_a_m_m_i_n_g, vol. 2
                     60: 
                     61: 
                     62: 
                     63: 
                     64: COHERENT Lexicon                                           Page 1
                     65: 
                     66: 

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