Question and Answer
Q Can a global variable be hidden by a local variable with block scope?
A Yes. If a local variable shares the same name with a global variable, the global
variable can be hidden by the local variable for the scope of the block within which the local variable is defined with block scope. However, outside the block, the local variable cannot be seen, but the global variable becomes visible again.
Q Why do you need the static specifier?
A In many cases, the value of a variable is needed, even if the scope of the block, in which the variable is declared, has exited. By default, a variable with block scope has a temporary memory storage—that is, the lifetime of the variable starts when the block is executed and the variable is declared, and ends when the execution is finished. Therefore, to declare a variable with permanent duration, you have to use the static specifier to indicate to the compiler that the memory location of the variable and the value stored in the memory location should be retained after the execution of the block.
Q Does using the register specifier guarantee to improve the performance of a program?
A Not really. Declaring a variable with the register specifier only suggests to the compiler that the variable be stored in a register. But there is no guarantee that the variable will be stored in a register. The compiler can ignore the request based on the availability of registers or other restrictions.
Q When you declare a variable with the extern specifier, do you define the variable or allude to a global variable elsewhere?
A When a variable is declared with the extern specifier, the compiler considers the declaration of the variable as an allusion rather than a definition. The compiler will therefore look somewhere else to find a global variable to which the variable with extern alludes.
