From the
computer’s point of view, a C program is nothing more than
a collection
of functions and declarations.
Functions
can be thought of as sealed capsules of program code which float on a background
of white space,and are connected together by means of function calls. White
space is the name given to the white of an imaginary piece of paper upon which a
program is written, in other words the spaces and new line characters which are
invisible to the eye. The global white space is only the gaps between functions,
not the gaps inside functions. Thinking of functions as sealed capsules is a
useful way of understanding the difference between local and global objects and
the whole idea of scope in a program.
Another analogy
is to think of what goes on in a function as being like
watching a
reality on television. You cannot go in and change the TV reality,only observe
the output, but the television show draws its information fromthe world around
it. You can send a parameter (e.g. switch channels) tomake some choices. A
function called by a function, is like seeing someonewatching a televsion, in a
television show.