Write once, run anywhere (WORA) is a term that refers to a particular program's supposed ability to run on all common OSs (operating systems). The term, sometimes also expressed as write once, run everywhere (WORE), was originally coined by Sun Microsystems in reference to Java.
When a program has WORA capability, then it should work on devices that use all of the popular versions of Windows, the Mac OS, Linux, Android, Solaris, NetWare, HP-UX, or any other OS or platform, whether the physical machine happens to be a mainframe, a desktop computer, a notebook computer, a tablet device, or a smartphone. The WORA capability requires that each machine's OS contain modifications that interpret the compiled WORA program's bytecode so that the machine's processor can perform the WORA program's instructions. In the case of Java, for example, each device's OS must have its own version of JVM (Java virtual machine) built-in.
While Java has come close to the WORA ideal, its success was derailed early in 2013 when security holes became apparent. The problem grew sufficiently serious to cause the U.S. government to recommend that computer users disable Java until appropriate patches could be developed and made generally available.
Sun Microsystems is not the only company that has pursued the WORA objective. Microsoft, in particular, has begun an aggressive campaign with the goal of improving its APIs (application program interfaces) to provide WORA capability.