Setting changed on my Ti-89 Titanium

[EmryAnn]

I am not sure what I did, but a setting changed on my Ti-89 Titanium. I used to be able to go back to my input line and add new characters like a parenthesis or a missing number. This is one of the big advantages to a ti-89, however, somehow, When I go to insert new characters, they erase the current one infront of the input line. This is a big problem! How do I change it back!??

 

[Muphrid]

Like most word processors, the 89 can be put into overwrite instead of insert mode. Google says you can change back and forth by 2nd+backspace. INS appears above backspace to remind you how to get into insert mode (blue to tell you to hit 2nd and then that key).