What is an auto variable in C ?

All variables declared within a function are auto by default. The extent of a variable is defined by its scope. Variables declared auto can only be accessed only within the function or the nested block within which they are declared. They are created when the block is entered into and destroyed when it is exited. i.e., memory is allocated automatically upon entry to a block and freed automatically upon exit from the block and note that default value is a garbage value.