Loops Do While Arduino Programming Robotics

Objectives
 Describe the purpose of loops.
 Use for loops.
 Use while loops.
 Use do while loops.
 Use the break and continue statements.
 Nest loops.

The for Loop
 The for loop repeats one or more
statements a specified number of times.
 Like an if statement, the for loop uses
parentheses.
 In the parentheses are three items
called parameters, which are needed to
make a for loop work.

Example for loop
for(i = 1; i <= 3; i++)
{ Serial.print(i); }
 The first parameter, called the initializing
expression, initializes the counter variable.
 The second parameter is the expression that
will end the loop, called the control
expression. It is tested before the loop.
 The third parameter is the step expression. It
changes the counter variable, usually by
adding to it.

Other step expressions
Countdown
for(i = 20; i >= 0; i--)
{Serial.print(i); }
Count by 10s
for(i = 10; i <= 300; i=i+10)
{Serial.print(i); }

while loops
 A while loop is similar to a for loop, but
in a while loop, something inside the
loop triggers the loop to stop.
 There are two kinds of while loops: the
standard while loop and the do while
loop.
 The difference between the two is
where the control expression is tested.

The while Loop
 The while loop repeats a statement or group
of statements as long as a control expression
is true.
 Unlike a for loop, a while loop does not use a
counter variable.
 The control expression in a while loop can be
any valid expression.
 In a while loop, the control expression is
tested before the statements in the loop
begin.

Example of a while loop
while (num > 1.0)
{
Serial.print(i);;
num = num / 2;
}
As long as the value of num is greater
than 1.0, the loop will continue.

The do while Loop
 A do while loop repeats a statement or
group of statements as long as a
control expression is true at the end of
the loop.
 Because the control expression is tested
at the end of the loop, a do while loop
is executed at least one time.

Example of a do while loop
int num =1, i=0;
do
{
Serial.print(i);
i++;
if(i==3){num = 0)}
}
while (num != 0);
int num =1, i=0;
while (num != 0)
{
Serial.print(i);
i++;
if(i==3){num = 0)}
}

Stopping in the Middle of a Loop
 The keyword break, also utilized with
switch statements, can be used to end
a loop before the conditions of the
control expression are met.
 The continue statement skips the
remainder of a loop and starts the next
iteration of the loop.

Nesting Loops
 Using nested loops is possible and very
common.
 We typically refer to the loops as the
inner loop and the outer loop.
 Make sure to trace the steps of the
program carefully to understand how
nested loops behave.

Summary
 A loop is used to cause a program to repeat a
group of statements a given number of times.
 Loops are iteration structures.
 Each loop through a group of statements is
called an iteration.
 A for loop repeats one or more statements a
specified number of times.
 A for loop uses three parameters to control
the loop.

Summary
 Step expressions can be simple or complex.
 Braces group the statements in a loop.
 A while loop repeats a statement or group of
statements as long as a control expression is
true. The control expression is tested at the
top of the loop.
 A do while loop repeats a statement or group
of statements as long as a control expression
is true at the end of the loop.

Summary
 The break keyword ends a loop before the
conditions in the control expression are met.
 The continue keyword skips the remainder of
the statements in the loop and continues with
the next iteration of the loop.
 Loops may be nested to have loops inside
loops.

Quiz
 Create a for loop, while loop and do while
statement that displays the following:
 1) 10, 9, 8, 7, 6, 5, 4, 3, 2, 1
55
 2) 5, 6, 7, 8, 9, 10
45
 3) 1000, 750, 500, 250
2500

 int count;
 int sum = 0;
 for(count = 10; count > 0; count--) {
 sum = sum + count;
 Serial.print(count);
 Serial.print(“, ”);
 }
 Serial.println(sum);

Loops Do While Arduino Programming Robotics

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