Random Number Generator

1. Random Number Generator

2. Using Software • We can generate random number by: • 1- table • 2- hardware • 3-- software • Function to generate RN by SW is: • 1-rand • 2- srand

3. algorithmic (software) generators • • Algorithmic generators are widely accepted because they meet all of the following • criteria. • • randomness - output passes all reasonable statistical tests of randomness • • controllability - able to reproduce output, if desired • • portability - able to produce the same output on a wide variety of computer systems • • efficiency - fast, minimal computer resource requirements • • documentation - theoretically analyzed and extensively tested

4. Rand function • It’s advantage that it produce the same number. • They solve this drawback by using (srand) function

5. Code by (rand) function 1 2 // Shifted, scaled integers produced by 1 + rand() % 6. 3 #include <iostream> 4 5 using std::cout; 6 using std::endl; 7 8 #include <iomanip> 9 10 using std::setw; 11 12 #include <cstdlib> // contains function prototype for rand 13 14 int main() 15 { 16 // loop 20 times 17 for ( int counter = 1; counter <= 20; counter++ ) { 18 19 // pick random number from 1 to 6 and output it 20 cout << setw( 10 ) << ( 1 + rand() % 6 ); 21 22 // if counter divisible by 5, begin new line of output 23 if ( counter % 5 == 0 ) 24 cout << endl; 25 26 } // end for structure

6. 27 28 return0; // indicates successful termination 29 30 } // end main 6 6 5 5 6 5 1 1 5 3 6 6 2 4 2 6 2 3 4 1

7. (Srand) function • It used to solve the disadvantage of (rand) function • Advantage of (srand) is: • 1- every time it run it produce different number • The disadvantage of (srand) is: • 1- the user must enter the variable to start generator.

8. Code by (srand) function

10. Develop to use (srand) function • To prevent the user from entering the variable they make enhancement to (srand) by using (srand(time(0))) • To use this function we must add the library (time.h)

11. Srand(NULL)function

13. Srand(NULL)function • Advantage: • Every time generate random number without intervention from the user