As title, I notice that the output of the first call to rand() seems to be a 9-digit number that steadily increases across the runs. The second call seems normal. Is this something well-known?

This is the code on my Mac

#include <cstdio>
#include <cstdlib>
#include <ctime>

using namespace std;

int main() {
  srand(time(NULL));

  printf("%dn", rand());
  printf("%dn", rand());
  return 0;
}

Here is my Makefile

BINARIES := test

all: $(BINARIES)

clean:
    $(RM) $(BINARIES) *~ *.dSYM

CXXFLAGS := -Wall -g -std=gnu++11 -O3
CXX := g++

RM := rm -r

This is the output of 8 runs

➜  Coding ./test
830930336
360000711
➜  Coding ./test
830963950
924951209
➜  Coding ./test
830980757
1207426458
➜  Coding ./test
831014371
1772376956
➜  Coding ./test
831064792
472319056
➜  Coding ./test
831081599
754794305
➜  Coding ./test
831098406
1037269554
➜  Coding ./test
831115213
1319744803

I tried srand(time(0)) and it does not change anything.