The Evolution of Thin Client Computing: From Mainframes to Zero Clients

Introduction to Thin Client Computing: The Benefits of Centralized IT Management

The ancestor of virtualization (the process of running a virtual instance of a computer system in a layer abstracted from the actual hardware) can be traced back to mainframe technology in the 1960's. Developed by IBM, mainframe solutions aimed at sharing computer resources among a large number of users. 

This was the founding act of virtualization, and many of the reasons why this technology was a breakthrough back then, are still valid today. Compared to "traditional" workstations, the benefits of desktop virtualization are abundant:

• Consolidation: virtualization dramatically reduces the amount of time it takes to do large-scale rollouts and upgrades one several hundreds or thousands of workstation
• Increased security: data is centralized, and user cannot download or install anything
• Reduced downtime: speedy disaster recovery if large scale failures do occur, and high availability
• Cost optimization: computer resources, IT staff resources and maintenance resources are shared
• Onboarding and mobility: users can access their applications and data from anywhere, as long as there is an Internet connection.

Thin Clients as a PC Alternative

With the rise of this new technology, thin clients stood out as an alternative to PCs and thick clients in general.

Thick clients can be connected (but not necessarily) to a server. In other words, a thick client has its own resources to remain functional even when disconnected. A thin client on the other hand, is primarily and exclusively designed to communicate with a server. 

On the basis of this definition, it appears that thin clients are not necessarily hardware. Thin client from a software perspective usually consisted of a minimal OS, a graphic user interface, a local web browser, sometimes emulators and a very basic set of utilities. 

Therefore, you could totally turn a PC (ie a thick client) into a thin client by booting it and implementing a thin client software in it.

However, today, thin clients are still associated with hardware manufacturers and in particular PC manufacturers. A thin client usually comes as a case with a processor, minimal memory and storage, and a bunch of connectors for display, keyboard, mouse, earplugs etc.

You can also find All in One thin clients (with thin client inner structure embedded inside of the monitor), but also thin clients such as smartphones, laptops... But the key remains the software. 

The History and Evolution of Thin Clients

The first thin clients were designed in parallel with the rise of mainframe technology that we mentioned above. It came through various denominations over the year: slim client in the 60’s, lean client during the big PC boom in the 80’s and thin client in the 90’s. 

The term "thin client" was introduced in 1993 by Tim Negris, who was at that time in charge of product marketing activities for Oracle, and at a time where Oracle wanted to step aside from Microsoft’s desktop oriented products like the PC.

And indeed, from the 90’s and on, thin clients stood more and more as an alternative to PC for businesses. This evolution stemmed from the increasing complexity to manage individual workstations one by one for operating system installation and software updates. IT administrators and managers started to see the benefits of  connecting devices together to create dynamic computing systems.

An IBM System z9 mainframe. Image credit: Wikipedia

To that extent, the rise of thin clients is closely tied to the growth of Virtual Desktop Infrastructure (VDI) technologies, and of virtualization technologies in general. 

Operating in a client-server environment, VDI consists of storing not only all data, but also the overall operating systems on a remote server, with only display, keyboard, and mouse information communicating with the local client device. 

Created in 1990, Citrix launched one of the very first VDI solutions based on Microsoft Windows or DOS, called WinFrame. 

Citrix WinFrame 1.8. Image credit: WinWorld

A reference in the world of VDI until today, Citrix is now challenged by virtualization actor VMware or cloud offers such as Microsoft Azure. A lot of complementary solutions (security, resource management…) also aggregated to form a rich ecosystem. The evolution of these VDI and VDI related technologies were the breeding ground of thin clients. 

Although the fundamental client-server basis of a thin client architecture did not evolve much over the years in its sheer simplicity, the software technology grew more and more mature over the years. In terms of graphics, a longtime weakness of thin client technology:

thin clients are now able to properly render graphic intensive applications such as AutoCad, animating programs or 3D drawing softwares. 

Security features have also improved dramatically, as vendors added several layers of security to preserve thin clients from ransomware, virus, malware attacks, and to preserve data integrity. Although a very old lady, thin client technology is constantly evolving to adapt to today’s environment.  

The Future of Thin Client Computing

Just like in the past, the future of Thin Client Computing seems to be closely tied to the future of virtualization and VDI in particular, and virtualization seems to be one of the most prominent tech trends in the future.

Many factors contribute to the massive adoption of virtualization for businesses, catalyzed by the pandemics we are facing right now: telecommuting and nomadism, the search for a greener alternative to PC, increased security threats (hacking, data breaches…), Bring Your Own Device policies, users increasingly working from their smartphone or tablet….

Consequently, cloud offers have never been this plethoric: cloud providers like Amazon Web Services or Microsoft Azure release a range of new solutions and features every quarter, and "As a service (aaS)" technologies are becoming more and more appealing to IT decision makers: Infrastructure as a Service, Platform as a Service, Desktop as a Service, Container as a Service, Data as a Service... 

Obviously, the hardware offer has to adapt to these new needs, especially since next generation operating systems require less and less resources. In that perspective, thin clients appear in theory as the royal hardware option.

And yet, oddly, PC sales remain stable over the years, and has even increased in the past months. 

Why is that? 

Maybe the answer lies not necessarily in thin client technology itself, but rather in the uncertainty, perceived pain, and costs of shifting to new technologies: why should one replace a well functioning desktop computer with new systems which will necessarily require time, investment and effort to get used to?

To overcome the reluctance of IT decision makers, thin client computing has to evolve and adapt to the new needs of the virtualization era: reinforced security, higher performance, easy manageability.

A thin client has to go beyond the client-server feature, and provide solutions for the user to work securely from anywhere, print, authenticate, switching seamlessly from one hardware to another...

In other words, a thin client has to be more than just an endpoint and deliver a whole set of new features to build the workstation of the future.