title: Random number generating in Fortran
body: <p>I write a code based on statistics with Fortran. Generating random number variables is necessary for sampling. I search between the same code (to find efficient structure) and see they use the &quot;RANDOM_SEED&quot; command in it. I search on the net to find something to help me with this command and find this: <a href="https://gcc.gnu.org/onlinedocs/gcc-4.6.4/gfortran/RANDOM_005fSEED.html" rel="nofollow noreferrer">RANDOM_SEED</a>. But I gained nothing from it. Also, I search on this site and find this: <a href="https://stackoverflow.com/questions/49163403/random-number-gives-vastly-different-behavior-between-gnu-and-pgi-fortran-comp">random_number() gives vastly different behavior between GNU and PGI Fortran compilers</a>. I find that Fortran creates pseudo-random numbers and not real random numbers.</p>
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  <h2>What is the problem?</h2>
  <p>What relation between pseudo-random numbers and the &quot;RANDOM_SEED&quot; command?</p>
  <p>Are random numbers in Fortran exist in some batch and this command changes the batch or it ignores some number from the start to avoid creating the same random number?</p>
  <p>I also find &quot;SET_SEED&quot;, what is this command?</p>
  <p>What is exactly &quot;<em>size</em>&quot;, &quot;<em>put</em>&quot; and &quot;<em>give</em>&quot; in the &quot;RANDOM_SEED&quot; command?</p>
  <p>I will appreciate any comments that give me a little help and forgive me for writing shortcomings.</p>