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There are two important things to realize about that last description:
one, that each of the three parts of the for statement between the parentheses are just expressions;
two, that the description has carefully explained what they are intended to be used for without proscribing alternative uses—that was done deliberately. You can use the expressions to do whatever you like, but at the expense of readability if they aren't used for their intended purpose.
Here is a program that does the same thing twice, the first time using a while loop, the second time with a for. The use of the increment operator is exactly the sort of use that you will see in everyday practice.
#include<stdio.h>#include<stdlib.h>void main(){
int i;/* the same done using ``for'' */
for(i = 0; i<= 10; i++){
printf("%d\n", i);}
} There isn't any difference between the two, except that in this case the for loop is more convenient and maintainable than the while statement. You should always use the for when it's appropriate; when a loop is being controlled by some sort of counter. The while is more at home when an indeterminate number of cycles of the loop are part of the problem.
Any of the initialize, check and update expressions in the for statement can be omitted, although the semicolons must stay. This can happen if the counter is already initialized, or gets updated in the body of the loop. If the check expression is omitted, it is assumed to result in a ‘true’ value and the loop never terminates. A common way of writing never-ending loops is either
for(;;)
or
while(1)
and both can be seen in existing programs.
The control of flow statements that we've just seen are quite adequate to write programs of any degree of complexity. They lie at the core of C and even a quick reading of everyday C programs will illustrate their importance, both in the provision of essential functionality and in the structure that they emphasize. The remaining statements are used to give programmers finer control or to make it easier to deal with exceptional conditions. Only the switch statement is enough of a heavyweight to need no justification for its use; yes, it can be replaced with lots of ifs, but it adds a lot of readability. The others, break, continue and goto, should be treated like the spices in a delicate sauce. Used carefully they can turn something commonplace into a treat, but a heavy hand will drown the flavor of everything else.
This is a simple statement. It only makes sense if it occurs in the body of a switch, do, while or for statement. When it is executed the control of flow jumps to the statement immediately following the body of the statement containing the break. Its use is widespread in switch statements, where it is more or less essential to get the control that most people want.
The use of the break within loops is of dubious legitimacy. It has its moments, but is really only justifiable when exceptional circumstances have happened and the loop has to be abandoned. It would be nice if more than one loop could be abandoned with a single break but that isn't how it works. Here is an example
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