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Show recording. Program event recording is the most expensive facility provided in the instruction set of the IBM 360. It is always the first one on the list of things that need to be removed from the system. But that has never happened, because according to an IBM computer architect, it has been justified more times than any other single feature in the system [25]. The first microprocessors did not provide any support for debugging in their architecture. Debugging features have advanced with each new generation. The simplest support is inclusion of a single step mode. One of the microprocessors providing sophisticated support is the Intel 80386 which provides four breakpoint registers to set various traps [37]. Their purpose is similar to that of IBM's program event recording with a limited functionality. The Multimax is a symmetric shared memory computer. Encore has developed an execution profiler Parasight that runs on one of the processors and measures the activity of other processors [3]. The concept is similar to the introspective computer, but the processors communicate through memory and synchronization between them is limited. Logical analyzers are a class of special purpose equipment that can capture the behavior of a computer. Their usage today is restricted to a very limited domain, mostly real time programming and hardware development. The main drawback is that they are not integrated in the computer and its programming environment. The introspective computer is designed to overcome that problem. Some debugging support was already present in computer architectures in the early sixties, but it did not attract a lot of attention. Only recently are debugging features returning back in computer architecture [55]. Sophisticated debugging environments are presented in [7, 61]. Recent efforts in debugging concentrate on parallel programs [40, 53]. Debugging represents a subset of conversational programming with the goal of finding errors in programs. 11 |
