Lecture7Full - Click to edit Master subtitle style 8/1/11...

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Unformatted text preview: Click to edit Master subtitle style 8/1/11 Lecture 7 COT 4600 Operating Systems Fall 2010 Dan C. Marinescu Office: HEC 439 B Office hours: Tu-Th 3:30-4:30 PM Lecture 7 8/1/11 n Last time: Interpreters. Communication links. n Today: Naming; n Use by: value/name n Binding and indirection n Generic naming model Name mapping algorithms Comparing names; name discovery n Practical design of naming scheme Contexts Name overloading n Next time UNIX File System Lecture 7 Tuesday September 14, 2010 Lecture 7 Lecture 7 8/1/11 Lecture 7 Naming n The three abstractions manipulate objects identified by name. n How could object A access object B: Make a copy of object B and include it in A use by value n Safe & there is a single copy of B n How to implement sharing of object B? Pass to A the means to access B using its name & use by reference n Not inherently safe & both A and C may attempt to modify B at the same time. Need some form of concurrency control. Lecture 7 8/1/11 Lecture 7 Binding and indirection n Names allow the system designer to: 1. organize the modules of a system and to define communication patterns among them 2. defer for a later time n to create object B referred to by object A n select the specific object A wishes to use n Indirection decoupling objects from their physical realization through names. n Binding & linking the object to names. Examples: A compiler constructs n a table of variables and their relative address in the data section of the memory map of the process n a list of unsatisfied external references A linker binds the external references to modules from libraries Lecture 7 8/1/11 Lecture 7 Generic naming model n Naming scheme & strategy for naming. Consists of: Name space the set of acceptable names; the alphabet used to select the symbols from and the syntax rules. Universe of values & set of objects/values to be named Name mapping algorithm O resolves the names, establishes a correspondence between a name and an object/value Context the environment in which the model operates. n Example: searching for John Smith in the White Pages in Orlando (one context) or in Tampa (another context). n Sometimes there is only one context & universal name space; e.g., the SSNs. n Default context Lecture 7 8/1/11 Lecture 7 Figure 2.10 from the textbook Lecture 7 8/1/11 Lecture 7 Operations on names in the abstract model n Simple models: value & RESOLVE (name, context) The interpreter: n Determines the version of the RESOLVE (which naming scheme is used) n Identifies the context n Locates the object Example: the processor n Complex models support: creation of new bindings: status BIND(name, value, context) deletion of old bindings: status & UNBIND(name, value) enumeration of name space: list & ENUMERATE(context) comparing names status: result & COMPARE(name1,name2) Lecture 7 8/1/11 Lecture 7 Name mapping n Name to value mapping One-to-One q the name identifies a single object...
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Lecture7Full - Click to edit Master subtitle style 8/1/11...

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