The main advantage of a screen wrapper is obvious. You can put a good looking, easy to use, high GUI veneer over 5250 screens, without having to spend the time and money required to analyze, rewrite and then retest all the business logic imbedded inside them as you would if you replaced them with VL components.
This is especially important for users to whom platform portability is of no real interest because they are content with a IBM i only solution.
 
Usage Examples
Some usage examples might include:    

• A screen wrapper can pick values out of hidden 5250 screens and present it in completely different ways.  For example, statistical information can be extracted and presented as a series of bar graphs (see Example 3: Show the IBM i Disk Usage).
• A screen wrapper can accept user input and then map it back into the 5250 screens so as to cause 5250 transactions to take place. For example, a VL component could allow high function, high volume order entry. When the user clicks Save, the order details are mapped into a series of 5250 screens and input.
• A screen wrapper might execute many 5250 screens from one click. For example a screen wrapper might display a list of 20 order numbers. When the user clicks OK all 20 orders are deleted by repeatedly executing a 5250 screen that only allows one order at a time to be deleted.

   
Role in Modernization Projects
For a customer happy with a IBM i dependent solution, a screen wrapper might be as far as they ever take application modernization.
Realistically, screen wrappers take time and money to develop, but probably significantly less than the equivalent VL component would, especially in the application testing phase of the modernization project.
Screen wrappers are not thrown away. When time and money permit, they may still be changed into proper VL components by removing their 5250 dependency.
You would expect modernization projects to go to market using a mix of 5250 screens, screen wrappers and VL components. For example, this might be the mix appropriate to an ISV:

• 85% - 5250 screens – to get to market ASAP.
• 10% - screen wrappers -  to rapidly replace some heavily used and critical areas (eg: Order Entry) with something much better to use that adds a lot of business value.
• 5%   - VL components – add high end value to the application (eg: E-Mail, PDF documents, MS-Excel spreadsheets, Web integration, etc).