Understanding internal versus external storage classes

In the storage class of fixed or named memory, C has explicit mechanisms to allocate that memory. These correlate to the following four C keywords:

• auto
• static
• register
• extern

Note that the auto keyword represents the automatic storage class, and the static keyword specifies the static storage class. We are currently interested in only the first two of these mechanisms. These keywords precede a variable specification, as follows:

<storage class> [const] <data type> <name> [= <initial value>];

In this specification, the following applies:

• <storage class> is one of these four keywords: auto, static, register, and extern.
• [const] is an optional keyword to indicate whether the named memory can be changed after initialization. If const is present, an initial value must be supplied.
• &lt...