Variables - Variables Names Binding Types and Type Checking...

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Variables Names Binding Types and Type Checking Scope and Lifetime
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Variable Names Syntactic restrictions Maximum (character) length Valid characters Alphanumeric, “connectors”, etc. Case-sensitivity Reserved words
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Variables What is a variable? Abstraction of computer memory cell or collection of cells Assembly Language = Machine Language + names Tuple of attributes: Name Address Value Type Lifetime Scope
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Variable Address Not necessarily exclusive Many variables can refer to same address ( aliasing) Not necessarily constant Variables often refer to different addresses in lifetime of program ( e.g., recursive function) L-value
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Variable Type Range of values a variable can have Can be dictated by machine limitations ( e.g., C short ) Often enforced by compiler/interpreter Strong typing vs. latent ( or dynamic) typing
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Variable Value Contents of (possibly abstract) memory cell addressed by variable R-value
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This document was uploaded on 02/13/2011.

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Variables - Variables Names Binding Types and Type Checking...

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