Lecture 29

break

What is break?:

break will terminate a loop or exit a switch

Why use break?:

allows you to stop the loop/switch if an error or irregular condition is detected

How to use break?:

break.syntax:

there are no arguments

break Examples

Simple break Example:

This program shows how to use a break statement:

break.c:

the loop is completely exited
no other iterations of the loop is executed

break Example with Nested Loops:

This program shows what happens when using a break statement within a nested loop:

break_inner.c:

break only exits inner loop
a break within the outer loop is needed to exit the outer loop as well

continue

What is continue?:

continue allows you to bypass the remainder of the current iteration of a loop

Why use continue?:

continue allows the loop to continue on to the next iteration
break, in contrast, will exit the loop entirely

How to use continue?:

continue.syntax:

there are no arguments

continue Example

continue Example:

This program shows how to use a continue statement:

continue.c:

the current iteration of the loop is skipped
the loop continues on to the next iteration

goto

What is goto?:

goto allows you to jump to different sections of your program
goto is a carry-over from older programming languages

Why use goto?:

you should not use goto unless absolutely necessary because goto program flow is hard to follow
you should try to use other flow control mechanisms before using goto:
- if/else
- break
- continue
the only possible time to use goto might be to break out of jump out of a doubly nested loop
- but even then you could use two if - break statements

How to use goto?:

for.syntax:

you need add a label somewhere in your program
labels cannot have the same name
the labelled code is still executed as normal code, even if the program reaches that portion of the program without first reaching the goto statement

goto Example

This program shows how to use goto

goto.c:

the out_of_both_loops statements are still executed when the program exits out of both loops without the goto statement

return

What is return?:

return causes the program logic to return to the point from which the function was called
return optionally returns information to the point from which the function was called

Why use return?:

to return a value
to return control of the program
to end the function

if within the main function, then the program will end

How to use return?:

return.syntax:

return does not need to return an expression, e.g. expression is optional

return Example

This program shows how to use return

return.c:

the last printf statement (You are out of both loops) is never executed because the program just ends
each function can only return one value/expression
the main function typically returns 0 to the operating system that calls the main function
- you can read more at http://stackoverflow.com/questions/204476/what-should-main-return-in-c-and-c

Fake a Switch with goto

Update this program to implement a switch using goto

switch_incomplete.c:

Assignment

Homework Problem 29.1, at the end of this problem you should submit to Laulima:

a file named UHusername_29_1.c
- zhaol_29_1.c
Write a program that allows the user to input a positive integer. The program will count from 1 up till the positive number. For numbers that are divisible by 3, print out Fizz instead of the number. For numbers that are divisible by 5, print out Buzz instead of the number. For numbers that are divisible by 3 and 5, print out FizzBuzz instead of the number. Try to use the continue statement or the goto statement to accomplish this.

For example:
```
Please enter the max number to count to:
[user enters in 31]
1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
17
Fizz
19
Buzz
Fizz
22
23
Fizz
Buzz
26
Fizz
28
29
FizzBuzz
31
```