Answer7

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	WHAT'S YOUR ENGINEERING QUOTIENT?
•Homerun? Problem 7—What can you infer about the rand() function after looking at the code and its output? #define ITER 10000 #define SEED 0x12345678 test() { int i; int counts[4]={0,0,0,0}; srand(SEED); for (i=0; i4; i++) { printf("%d bin probability = %f\n", i, counts[0]/(float)ITER; } } After running the code many times with different values for ITER and SEED, you always get the same output: 0 bin probability = 0.25000 1 bin probability = 0.25000 2 bin probability = 0.25000 3 bin probability = 0.25000 Answer: If ITER and SEED remained constant, you would expect to get identical results every time. But given that the SEED is changed you would expect to get different results. If you were to flip a coin a 100 times and got exactly 50 heads and 50 tails, you might think it a little coincidental. But to repeat the experiment again and again without variation can only mean one thing -- it is not random. In this case, only the two lowest order bits of the random number were being used. Some C compilers use random number generators that do not produce random numbers in all of their bits. 8-99 For questions or comments about Test Your EQ, e-mail eq@circuitcellar.com.