How to turn capslock on in iphone 4?

So i can type in capital letters without hitting ⬆ after every letter

Tap it twice then the buttons glows blue in colour & later in the message tap it once to exit the function.

The iPhone does include a Caps Lock feature -- the trick is finding it so you can turn it on. Here's how:

Tap Settings
Tap General
Tap Keyboard
Tap the Enable Caps Lock slider

The Caps Lock slider is like a toggle switch. Tapping it once enables the feature, tapping it a second time shuts it back off.

On the iPhone keyboard, there's a button next to the letter Z (it's an arrow facing upwards). Double click this button to turn on caps lock. And double click it again to turn it off. You know it's turned on when that button is in blue. Hope this helped.

Double tap the Upward Arrow Key to turn on caps.
Double tap it once more to deactivate…

It should be located on the bottom left parallel to the "Z" key and below the "A" key.

"Note" I'm using an IPhone5 keyboard as a reference, so my answer May or may not be valid…