C programming notes - School of Physics

C programming notes
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23 of 40 19/03/2007 10:06 AM
else /* NOTE: possible ambiguity here, the compiler uses */
y = 3; /* the closest if statement that does not have */
else { /* an else clause */
x = 4;
y = 5;
}
Example Program ifelse.c
Break and continue
These two statements are used in loop control.
"break" exits the innermost current loop.
"continue" starts the next iteration of the loop.
Here is an examaple program with break and continue (breakcon.c)
Infinite loops
Here are three ways of writing an infinite loop, choose whichever one you like:
for (;;;) {
statement;
}
while (1) {
statement;
}
do {
statement;
} while (1);
Infinite loops can be useful. They are normally terminated using a conditional test with a "break" or "return" statement.
For example:
while (1) {
statement;
if (logical_condition) break;
}
goto
C does have a "goto" statement, but you normally don't need it. Using "goto" is usually a result of bad programming
(although in some circumstances it can be a sensible choice).
The switch statement
The switch statement allows you to choose between multiple paths of execution depending on the value of an
expression. It could be replaced by a series of if statements, but switch can make the flow of the program easier to
understand.
switch (expression) {
case const-expression: statements
case const-expression: statements
default: statements
}
Beware that control will flow from one case to the next unless you explicitly include a break statement to cause control
to skip to the end of the switch statement.
Here is an example of using switch:
switch (i) {
case 0: printf("i had the value zero\n");
break;
case 1:
case 2: printf("i was either one or two\n");