The ISPL Machine

Principles of Operation

by R. M. Balzer

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The first of a series conceptually describing the Incremental System Programming Language (ISPL) computing system, an integrated environment for multiuser research programming. The ISPL language and machine are jointly designed, with hardware providing the control and scheduling facilities traditionally handled by Job Control Language and other software. Close correspondence between program statements and machine actions makes for clarity and efficiency and facilitates incremental compilation, which in turn allows online, interactive programming and debugging. During postfix program translation, ISPL inserts NEW STATEMENT operators that define interruptible points. User address spaces are carefully segregated. Separately accessed memory areas are assigned in logical units, with pointers. Most programs and data remain in virtual memory; only those portions of program and data actually referenced are contained in real memory. Resources are allocated by machine primitives called semaphores, which may also carry data. Data semaphores compose Ports, which provide hardware/software/user communications (described in R-605). (See also R-563, R-603, R-622, RM-5611.)

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