Today's lesson explored numeric variables, which are used by a C program to store data during program execution. You've seen that there are two broad classes of numeric variables, integer and floating-point. Within each class are specific variable types. Which variable typesuch as int, long, float, or doubleyou use for a specific application depends on the nature of the data to be stored in the variable. You've also seen that in a C program, you must declare a variable before it can be used. A variable declaration informs the compiler of the name and type of a variable.
You also learned about C's two constant types, literal and symbolic. Unlike variables, the value of a constant can't change during program execution. You type literal constants into your source code whenever the value is needed. Symbolic constants are assigned a name that is used wherever the constant value is needed. Symbolic constants can be created with the #define directive or with the const keyword.