1. Functions
October 23, 2017

2. Top-Down Design
Top-down design refers to designing a program by breaking down the end result into a series of smaller subtasks, then breaking those down further, and so on.
The final subtasks should be trivial to implement (e.g., incrementing a variable).
In C++, these subparts are known as functions.
Other languages may refer to them as procedures or methods.

3. Predefined Functions
C++ includes a number of predefined functions. The following functions are found in the cmath library:
sqrt(x) computes the square root of x (which can be an int or double)
pow(x, y) raises x to the power of y
abs(x) computes the absolute value of x
ceil(x) computes the first whole number greater than or equal to x
ceil(2.1) == 3
floor(x) computes the first whole number less than or equal to x
floor(2.9) == 2

4. Predefined Functions Consider the following code:
root = sqrt(9);
The value in parentheses is called the argument of the function.
The value the function computes (in this case, 3) is called the value returned.
The expression sqrt(9) is called a function call.
Not all predefined functions take arguments.
The rand() function (which computes a random number between 0 and 231 – 1) is one such function.

5. Random Number Generation
N.B. On the AP exam, the pseudocode RANDOM(x, y) generates a random number between x and y.
For instance, RANDOM(0, 5) generates a random number between 0 and 5.