Hello I have taken several programming lanuages and I am trying to learn pascal for a job I applied for

I was wondering how to do something

OK say you have the following string 'its going to rain today'
what I need to do is delete all occurences of the letters tsia

what I have now is a for loop and a while loop what do I need to add to delete the letters

For each letter search through the string, by either using the pos function or string indexing, then get rid of the occurrences with delete or copy. I would just flag the occurrences then copy the non flagged ones to a new string...