Complicating factors include various forms of

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Complicating factors include various forms of indirect addressing, virtual memory management, and cooperating processes, which are two or more processes that “want” to share a memory region. Memory protection adds overhead to each write operation. 12. Absolute addressing means that references to memory in software correspond to physical memory locations. With indirect addressing, the OS calculates and stores the process offset in a register when the program is first loaded into memory. During program execution, the CPU automatically adds the process offset to all memory references to convert them into physical memory locations. 13. Indirect addressing allows flexibility in placing programs in memory. Each program can be written with the assumption that it’s loaded at the beginning of physical memory. Multiple programs can run simultaneously, and programs can be moved in memory during execution, which generally allows more efficient management of memory resources and simpler program construction. The cost is the overhead needed to convert memory references to physical memory
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addresses. This conversion requires executing instructions to perform the conversion or additional circuitry in the CPU’s control unit to perform address translation automatically. The result is more complexity and/or higher cost and a possible reduction in execution speed. Structured system development uses an abstract requirements (analysis) model and an abstract implementation model. The requirements model is constructed using data flow diagrams, entity- relationship diagrams, and related textual descriptions. The implementation model is constructed using system flowcharts, structure charts, and related textual descriptions. The prototyping approach to system development avoids the use of abstract models and uses a prototype instead. Object-oriented development models the system as a set of related objects (collections of data and related processes). This model mirrors the software objects that are actually implemented. 4. What are the differences between source code, object code, and executable code? Source code contains program instructions in a format defined by the rules of a high-level programminglanguage. Object code contains a mixture of machine instructions and calls to previously defined machineinstructions in stored library subroutines. Executable code contains machine instructions that are ready tobe loaded into memory and executed. 5. Compare and contrast assemblers, compilers and interpreters. An assembler translates a 2GL into a file of executable code.A compiler translates a source code file into one or more object code files.An interpreter translates and executes a source code program one
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source code instructions at a time.
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