Emulation-Tool for software development

A major computer operations problem is the conversion of programs from one language to another when a replacement computer is acquired. Emulation was developed as one solution to the conversion problem. Emulation allows the machine instructions of the emulated (target) machine to be executed on the emulating (host) machine. Thus permanent program conversion is avoided. Frequently, emulated programs execute several times faster than their non-emulated counterparts. This occurs because the host is faster than the target or its microinstructions are more efficient than the target's machine instructions, or for both reasons. Other methods of program conversion which compete with emulation are: recompilation, reassembly, translation and simulation (interpretation). Although "translate" is frequently used as a general term to denote all types of language conversion, including assemblers and compilers, here it will be used more specifically to mean a conversion from language A to language B where A and B are not machine languages. It should be noted that recompilation, reassembly and translation effect a permanent conversion, i.e., the result of the process is a program in another language, whereas emulation and SImulation employ another language, microinstructions and interpretive routines, respectively, only during the period of program execution. Another way of viewing this difference is that· execution of a converted program using recompilation, reassembly or translation is a two step process-conversion followed by execution-whereas emulation and simulation are one step processes; as far as the user can discern, conversion and execution take place simultaneously in a single computer process. Another application of program conversion techniques is in a software development organization, where a mUltiplicity of hardware and software systems are produced. This occurs, for example, in organizations which are developers of tactical software systems for ships and aircraft. Typically, many computers comprise a single system. The variety of computers is even greater across the many systems with which the software development organization could become involved. It would be quite expensive for the software organization to acquire all the required computers and programming languages, particularly in view of the transient