How to stop the iPhone from flipping?

I heard on the iPhone 4S that you can make it so when you turn the screen it doesn't flip the screen in notes or texting or something it doesn't flip the keyboard. It's called screen lock or something? If so how do you do it?

If you have ios7:
1. Flick up from the very bottom of the screen (does not matter what you're doing with the phone, it will always work as long as the phone is on)
2. A menu will pop up. In the top right hand corner, there will be a little circle with a lock with a circular arrow around it
3. Tap the circle, it will turn from dark grey to white
4. Your iPhone screen will no longer rotate if you turn it from side to side.

If you have an earlier software:
1. Double tap your home button
2. A little menu will pop up
3. Swipe from the left to the right (I can't remember if it was once or twice, but if you swipe all the way to the left, then back to the right once, you'll be there)
4. There will be a circle with a lock with a circular arrow around it, tap it
5. Your phone screen will no longer rotate

Slide the bottom up and press lock screen

It is called portrait orientation lock. This is how you activate it:

1. Swipe your finger from the bottom of the screen upwards: this will open Control Center.
2. There should be an icon on the top row of the Control Center menu of a lock with an arrow around it.
3. Click that icon and you are done.

This only works if you have iOS 7, which I think is what the iPhone 4S comes with.