This is a comment. This is a comment, too. Let's return to the sample program that we were discussing. The iostream header is included whenever you want to do input or output. Since most programs use input and output, you will nearly always want iostream .
Some compilers support both.
In our examples we will use the version of the header without the .h extension. When using headers without the .h extension, also use the std namespace as shown. This namespace is needed in order to have access to many items that we will use in our programs. The program above consists of just a main function. They can also have other functions.