title: How HTML file upload works?
body: <p>HTML uses <em>form</em> to send data to web server. The data can be included in the url parameters or embedded in HTML Request body. But for a file, I don't know how it works. I want to know this because I see some difference between uploading file on web and desktop applications.</p>
  
  <p>The desktop application usually provides a text box to allow the user input the locale path of the file. But for web applications, the text box is usually read only.It displays the file path when the file gets selected with the <em>browse</em> button. Is that just a design issue between desktop and web?</p>