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	Floating point number with twice the precision of a float	8
void	No Type (useful for defining function with no return	N/A

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

int iter = 0;       // An integer with an inital value of zero 
double energy;      // A double-precision float with no initial values
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'ed out. You should never assume the size of a data type, you should use the sizeof() function to get the size of a data type in your program.