Virtual-machine (VM) technology has been around since well before Java or C# were even dreamed of. I used the UCSD Pascal P-system, which delivered portability. But its interpreted application performance was lacking compared to native code apps. Native code compilers were limited by the host system memory and processing power. This didn't stop bytecode virtual machines from being at the core of SmallTalk, a prominent object-oriented language. Even Forth uses a virtual-machine architecture. Yet virtual-machine-based solutions never took the embedded or PC market by storm until Java.
A number of factors came into play with Java, and the Java virtual machine (JVM) is just one of them. It is the part we concentrate on this month, leaving other major issues like framework support, standards, and a better programming language environment for another time.
What makes a difference in the latest crop of JVMs is the higher-performance platforms and the sophisticated environment. Where 8-bit processors once struggled to support a VM, VMs now find a home in today's 32-bit processors. Just-in-time (JIT) and ahead-of-time (AOT) compiler support is now mixed with interpreter support. Even more important is the high quality of compiler-generated code even for a sophisticated language like Java.
One thing that should not be overlooked with the latest VMs is garbage collection. Java, Microsoft's .Net (and ECMA-335), and Vita Nuova's Inferno support garbage collection. Pointer problems are the bane of C and C++, and garbage collection can eliminate most of these kinds of problems. Garbage collectors for embedded systems have significantly improved to the point of being usable in real-time systems.
VMs have proven their worth in high-performance systems like network switches and high-reliability systems as well. If you are not using one now, then it is time to take a close look at the technology and benefits of virtual machines.
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