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.
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