How To Use Random Function In Dev C++

Random number generators fulfill a number of purposes. Everything from games to simulations require a random number generator to work properly. Randomness finds its way into business what-if scenarios as well. In short, you need to add random output to your application in many situations.

Mar 26, 2017  code randomize/code and code random/code are not part of the standard library. Perhaps your teacher wrote functions with these names for use in your class, or maybe you really mean code random/code and code srandom/code whi.

Random Function In Dev C++

Creating a random number isn’t hard. All you need to do is call a random number function as shown in the RandomNumberGenerator example:

Actually, not one of the random number generators in the Standard Library works properly — imagine that! They are all pseudorandom number generators: The numbers are distributed such that it appears that you see a random sequence, but given enough time and patience, eventually the sequence repeats.

In fact, if you don’t set a seed value for your random number generator, you can obtain predictable sequences of numbers every time. How boring. Here is typical output from this example:

The first line of code in main() sets the seed by using the system time. Using the system time ensures a certain level of randomness in the starting value — and therefore a level of randomness for your application as a whole. If you comment out this line of code, you see the same output every time you run the application.

The example application uses rand() to create the random value. When you take the modulus of the random number, you obtain an output that is within a specific range — 12 in this case. The example ends by adding 1 to the random number because there isn’t any month 0 in the calendar, and then outputs the month number for you.

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The Standard Library provides access to two types of pseudorandom number generators. The first type requires that you set a seed value. The second type requires that you provide an input value with each call and doesn’t require a seed value. Each generator outputs a different data type, so you can choose the kind of random number you obtain.

The table lists the random number generators and tells you what data type they output.

Pseudorandom Number Generator Functions
FunctionOutput TypeSeed Required?
randintegeryes
drand48doubleyes
erand48doubleno
lrand48longyes
nrand48longno
mrand48signed longyes
jrand48signed longno

Now that you know about the pseudorandom number generators, look at the seed functions used to prime them. The following table lists the seed functions and their associated pseudorandom number generator functions.

Seed Functions
FunctionAssociated Pseudorandom Number Generator Function
srandrand
srand48drand48
seed48mrand48
lcong48lrand48