What is a While loop?
The while construct consists of a block of code and a condition/expression. The condition/expression is evaluated, and if the condition/expression is true, the code within the block is executed. This repeats until the condition/expression becomes false. Because the while loop checks the condition/expression before the block is executed, the control structure is often also known as a pre-test loop.
What they do is simply do a test like an if-statement, but instead of running the code block once, they jump back to the "top" where the while is, and repeat. A while-loop runs until the expression is False.
What does the while loop do?
For example, say we want to know how many times a given number can be divided by 2 before it is less than or equal to 1. If we know a specific number, such as 32, we can say 5 times, but for a given symbolic variable "NUMBER" which represents any number in the world, how many times is not known a priori (before hand). In this case, we could use a while loop to determine that answer:
The "pseudocode" for such an algorithm is: while the number is bigger than one keep dividing it by two. additionally, keep a count of how many times we do the division.
Therefore, the while loop;
- Like all loops, "while loops" execute blocks of code over and over again.
- The advantage to a while loop is that it will go (repeat) as often as necessary to accomplish its goal.
n = 10;
f = n;
while n > 1
n = n-1;
f = f*n;
disp(['n! = ' num2str(f)])
n! = 3628800
Let n be 10
f is equal to n
while n is greater than 1
the new value of n is the old value of n less 1
new value of f is a product of the old value of f and the new value of n