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Cherryl Lewis
Cherryl Lewis, Computer Software Engineer
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* What is the definition and function of a loop control variable

Resolved Question:

* What is the definition and function of a loop control variable?
* How does a loop control variable used to determine when a loop should terminate?
* What is a counter? How is it used?
* How does the value of the counter change as a loop is executed?
* How are loops implemented in different programming languages?
Submitted: 7 years ago.
Category: Programming
Expert:  Cherryl Lewis replied 7 years ago.

Hey I just got this one but I see someone answered a similar question for you. Is this one a duplicate or are you looking for my take on it? Either way is no problem.

 

Thanks,

 

Cherryl

 

 



Edited by Cherryl Lewis on 1/24/2010 at 1:34 AM EST
Customer: replied 7 years ago.
Yes I wanted your take on this.

Thanks
Expert:  Cherryl Lewis replied 7 years ago.

I accidentally posted before I was done and deleted it. Just one moment and I'll finish and post again.

 

 

Expert:  Cherryl Lewis replied 7 years ago.

Here is my take on it--let me know if you have any questions on it.

 

* What is the definition and function of a loop control variable?

 

A loop is a programming construct that consists of a series of one or more programming instructions, and a loop control variable is used to determine when to exit the series of instructions.

 

* How does a loop control variable used to determine when a loop should terminate?

 

The loop control variable must be tested either before processing any instruction or at the end of processing the instructions. The programmer sets up the test and can control the variable in order to ensure that it is handled correctly.

 

* What is a counter? How is it used?

 

A counter is a form of a loop control variable. It can be either incremented or decremented, that is either added to or subtracted from. The counter is tested to decide whether to end the loop process or not.

 

* How does the value of the counter change as a loop is executed?

 

Depending on the programming language used, the programmer can set it up to have full control of the counter and change it during the processing of loop itself, or can rely on the programming language to automatically update the counter. When the counter is updated automatically it is best not to update it in the loop instructions, as this may introduce errors such as a premature exit of the loop or a runaway process that never passes the test to exit.

 

* How are loops implemented in different programming languages?

 

In Visual Basic, a for-next loop is a common construct which uses a counter that is set up to allow the program to automatically update the counter, for example:

 

Dim X as Integer

Dim Y as Integer

 

For X = 1 to 100

Y = X * 2

Next

 

In C++, the same loop looks like this:

 

int y = 0;

For (int x = 0; x < 100; x++)

{

y = x * 2;

}

 

Other loop constructs consist of do-while and do-until.

 

Visual Basic:

 

Dim X as Integer

Dim Y as Integer

 

Do While (X < 100)

Y = Y + (X * 2)

X = X + 2

Loop

 

 

C++:

 

int x = 0;

int y = 0;

 

while (x < 100)

{

y = y + (x * 2);

x = x + 2;

}

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