This appendix gives a general overview of the core C++ language.
Except in the case of void expressions, an expression is something that produces a value. Expressions are the fundamental building blocks of statements, because an expression can be turned into a statement by adding a semicolon (;).
Smaller expressions can form part of larger expressions. For example, an expression is formed by addition:
expression + expression
Each of these can be any two smaller expressions that produce a numeric value. (Also, pointers may be added to integers; see Appendix A.) The result is an expression that can be used, in turn, in still larger expressions.
In C and C++, expressions can produce side effects. For example, ...