How is a named constant different from a variable? How would you create a named constant (and show an example)?

What will be an ideal response?

By definition, a variable's value can vary, or change. Sometimes you want to create a named constant (often simply called a constant), an identifier whose contents cannot change. You create a named constant similar to the way you create a named variable, but by using the keyword const. Although there is no requirement to do so, programmers usually name constants using all uppercase letters, inserting underscores for readability. This convention makes constant names stand out so that the reader is less likely to confuse them with changeable variable names. For example, the following declares a constant named TAX_RATE that is assigned a value of 0.06:
const double TAX_RATE = 0.06;