1. Random Numbers

It is often useful to have the computer generate one or more random numbers for us. A random number is a number that could be any number--we don't know what it is in advance, although usually we specify a range of possibilities. It's like when we say "Pick a number from 1 to 100." We don't know in advance which number the person will pick, but we do know that it will be from 1 to 100.

Random numbers can be used in many different ways in programming. For example, we might want the robot to move to a sequence of random positions around the grid. Or, if we have an activity that asks the user to input a value, we can test the code with different values by simulating the user's value with randomly generated numbers.

RoboBlocky has several code blocks in the Math menu that will generate random numbers. In this lesson we'll look at two of them.

2. Generating Random Integers

The random integer block will generate a random integer within a range of two specified values, such as from 1 to 100:

3. Generating Random Decimal Values

The random double block will generate a random decimal value within a range of two specified values, such as from 0 to 10:

The double value will be generated with 16 digits, such as 8.375339510276483.

If we want to display the value but not display all 16 digits, we can use the set digits after decimal block (in the Text menu). Or we can use the round digits after decimal point block (in the Math menu) to round the number to a specified number of digits.

(Note that the set digits after decimal operation does not change the value of the number, but just determines how many digits to display; the number will still have 16 digits. But rounding the number does change its value. Remember also that "double" refers to how decimal numbers are stored within the computer's memory. It does not have anything to do with doubling a number.)