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STXIT was an IBM System/360 series mainframe computer macro instruction under the DOS/VSE operating system, and was also available for the UNIVAC Series 90 mainframes running its TOS/DOS operating system and later on its VS/9 operating system. ==Background== The macro was an abbreviation of the term "Set Exit," and was used by programs written in assembly language. It is used to create a recovery routine in the event of program errors, similar to signal handlers in C and Try/Finally blocks in C++, Java and other object oriented languages. The STXIT macro would provide an error recovery address for several major types of errors and certain operator signals. The errors covered depended upon the operating system. In general, the errors which it provided recovery included * address protection violate (accessing memory not owned by the application) * privilege violation (attempts to execute privileged instructions) * divide check (division by zero) * floating point check (floating point underflow or overflow) * timer runout (where a timer set by the program has expired) this particular interrupt is not actually an error, it is how a program responds to a watchdog timer * Interrupt resume, a function on the UNIVAC Series 90 where an interactive user has issued a break to a program to go to command mode, and issued an INTR command to cause the program to resume at the INTR point. If the program has not specified an INTR resume address, the INTR command is rejected. This is similar to the REENTER command on the RT-11 operating system on Digital computers. The timer interrupt STXIT provided a mechanism for sampling program execution and was used by various legacy performance analyzers. Essentially a PSW was gathered for each time interval and used for later analysis to determine hot spots. The program check STXIT provided a mechanism for program animation via the deliberate introduction of invalid opcodes (on the fly) to locations in the target programs. Once the exit recovery was entered, the original opcode would be restored ready for later resumption and a new location set. This method was deployed in early versions of DOS/VSE versions of IBM OLIVER (CICS interactive test/debug) but later replaced by a non-invasive Hypervisor technique. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「STXIT」の詳細全文を読む スポンサード リンク
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