Navigating C++ and Object-Oriented Design

4.7. Const Objects

User programs may create constant objects. Here are several examples with class Fifo.

const Fifo x("data bytes");                  // 80 char Fifo with data 
const Fifo y("small fifo", 20);              // 20 char Fifo with data
const Fifo z = "more data bytes";            // 80 char Fifo with data

const Fifo *r = new const Fifo("abc");          // Fifo (80), free store
const Fifo *s = new const Fifo("xyz", 8);       // Fifo (8), free store
const Fifo *t = new Fifo("123");                // Fifo (80), free store
Fifo *u = new const Fifo("456");                // illegal (const Fifo)

The keyword const before object declarations or after operator new creates constant objects. Attempts to modify constant objects (that is, change state variables) generate compilation errors. All statements use Fifo constructors ...