C++ Primer Plus

Static Storage Duration, No Linkage

So far, we’ve looked at a file-scope variable with external linkage and a file-scope variable with internal linkage. Now let’s look at the third member of the static duration family: local variables with no linkage. You create such a variable by applying the static modifier to a variable defined inside a block. When you use it inside a block, static causes a local variable to have static storage duration. This means that even though the variable is known within that block, it exists even while the block is inactive. Thus a static local variable can preserve its value between function calls. (Static variables would be useful for reincarnation—you could use them to pass secret account numbers for a Swiss bank ...