Citrix XenApp is the leader of application virtualization or application delivery. Several years ago, when the word Virtualization didn't exist, people used to talk about application hosting. Citrix was founded in 1989 and they developed the first successful product in 1993 called WinView. It provided remote access to DOS and Windows 3.1 applications on a multi-user platform. Citrix licensed Microsoft's Windows NT 3.51 source code from Microsoft; and in 1995 they shipped a multiuser version of Windows NT based on the MultiWin engine, known as WinFrame. This allowed multiple users to logon and execute applications on a WinFrame server. In 1996 Citrix licensed the MultiWin technology to Microsoft, establishing the foundation of Microsoft's Terminal Services.

I remember perfectly the first time I was in touch with application hosting was in 1997, and I was working at Microsoft in Argentina as Technical Support Engineer. I was invited for MCSE certification training on a Saturday morning. We had been building a lab with several machines, when I saw several Microsoft Beta CDs on a table.

I took one of them called Hydra and I asked the guy in charge of the training about it, and he told me that the CD contained an application to convert a Windows NT 4.0 into a sort of mainframe. I asked him if we could install it on a machine and he told me we did not have enough RAM to install it. I recall walking inside empty offices to open computers and remove the RAM so that we could install Hydra on a computer.

It was couple of years later, in 1999, when I discovered that Hydra is Windows 4.0 Terminal Server Edition. I was working with my first Citrix server and that was when I first fell in love with application hosting.

In this chapter we will learn: