Data Types and Variables

There are several data types that are commonly used in C and C++ programs

Name	Data	Typical Size (bytes)
int	Integer	4
char	Character	1
float	Floating-point number	4
double	Double-precision Floating-point number	8
void	No Type (useful for defining functions with no return)	N/A

Note: The size of data types can vary among computer systems, so you should never assume particular values. The sizes given in this table are only guidelines. Use the sizeof() function to determine the size of a type or variable inside your programs.

A variable is a location in memory used to store data. Variables are assigned names and data types by the programer either when they are first used or before hand. Here are some examples:

int iter = 0;       // An integer with an initial value of zero 
double energy;      // A double-precision floating-point number with no initial value
int z_vals[50];     // An array of 50 integers
double geom[10][3]; // A 2-d array of doubles, there are 10 sets of 3 values each

Note: You should never assume that an uninitialized variable has been zero'd out.