3.1 Expression Statements  [This section corresponds to K&R Sec.
3.1]  Most of the statements in a C program are expression
statements. An expression statement is simply an expression
followed by a semicolon. The lines          i = 0;         i = i
+ 1;         printf("Hello, world!\n"); are all expression
statements. (In some languages, such as Pascal, the semicolon
separates statements, such that the last statement is not
followed by a semicolon. In C, however, the semicolon is a
statement terminator; all simple statements are followed by
semicolons. The semicolon is also used for a few other things in
C; we've already seen that it terminates declarations, too.)
Expression statements do all of the real work in a C program.
Whenever you need to compute new values for variables, you'll
typically use expression statements (and they'll typically
contain assignment operators). Whenever you want your program to
do something visible, in the real world, you'll typically call a
function (as part of an expression statement). We've alrea