Random Number Generation

Chapter 5

The header file cstdlib contains a the rand() function which returns a pseudorandom number (i.e., a seemingly random number).

• rand() returns an int value between 0 and RAND_MAX (often 32767).
• Examples:

  rand() % 100 // a "random" integer >= 0 and < 100`
  rand() % 100 + 900 // a "random"  between 900 and 999 inclusive`

• srand() seeds the random number generator. It accepts 1 parameter, an unsigned int, which determines the set of random numbers to be returned by rand().
  • Commonly the time is used to seed the random number generator. That way you have a different seed every time the program executes.

    const unsigned int SEED = time(nullptr);
    srand(SEED);

  • Generally, you should only call srand() once in your code so the numbers appear to be more random.

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This is a fun example that I think will help solidify some concepts for you. Also, it shows how you can use pseudo-random numbers to create a game.

“The lot is cast into the lap, but its every decision is from the LORD.” - Proverbs 16:33 (ESV)

• Random just means WE cannot predict the outcome.