Chapter 10 – Loops

(You must still copy notes by hand into notebook!)

Loops – Allow code to be repeated a number of times (called iterations).

FOR loops – Loop as long as a condition is true.

FOR loops have a control variable which will be part of the condition….this variable is initialized at the start of the loop.

3 PARAMETERS

Initialize control variable

for (j = 0; j < 10; j++) Change variable value.

{

//looping code here; Condition that causes

} structure to loop when

true

Will start j at 0, add one each time, and loop as long as j < 10

Other sample FOR LOOPS

for (k = 10; k > 0; k--)

{

//code;

}

for (m = 5; m < 100; m = m + 5)

{

//code;

}

for (j = 0; j != 10; j++)

{

//code;

}

for (t = a; t > b; t++)

{

//code;

}

WHILE LOOPS

Similar to for loops, but are typically triggered to stop by something that happens inside the loop.

· User answers “No” or “Yes” to a question

· Key condition is met…etc

While loops – keyword is while, followed by condition

Condition must be true in order for loop to begin and loop will continue as long as condition stays true.

Examples:

while (x != 3)

{

//code;

};

Note: condition must be true to start loop – useful when you’re not sure whether you would want to use the code or not.

Do/While Loops: keyword is DO, followed by code, followed by while with condition. Condition must be true in order to repeat code.

do

{

//code;

}

while ( x != 3);

Summary:

· Use a FOR loop when you know how many times you will loop (or when the program determines this.)

· Use a DO / WHILE loop when you want to loop at least once, and the trigger to stop the loop is inside the loop.

· Use a WHILE loop when you might not ever want to loop, but if you do, the trigger to stop the loop is inside the loop