No.  This is one of the greatest things about Joomla CMS.  When you want to add content or articles to your website, you will be presented with an online editor which is very easy to use (see snapshot of content editor below).  We tell our clients that if they can write an email, they can add content to thier Joomla website too.  If you do prefer to use HTML, it's very simple.  Just click on the "html" button on the editor, and you can paste in your own code.