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What Is The Modes Of A Machine?

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Reduction in Strength: => Reduction in strength replaces expensive operations by equivalent cheaper ones on the target machine. Certain machine instructions are considerably cheaper than others and can often be used as special cases of more expensive operators. => For example, x² is invariably cheaper to implement as x*x than as a call to an exponentiation routine. Fixed-point multiplication or division by a power of two is cheaper to implement as a shift. Floating-point division by a constant can be implemented as multiplication by a constant, which may be cheaper. X2 → X*X Use of Machine Idioms: => The target machine may have hardware instructions to implement certain specific operations efficiently. For example, some machines have …show more content…

Each symbol in a program has associated with it a series of attributes that are derived both from the syntax and semantics of the source language and from the symbol’s declaration and use in the particular program. The typical attributes include a series of relatively obvious things, such as the symbol’s name, type, scope, and size. Others, such as its addressing method, may be less obvious. The constituents of a symbol table are namely, the symbol-table entries. A symbol-table entry collects together the attributes of a particular symbol in a way that allows them to be easily set and retrieved. Table 1 lists a typical set of attributes for a symbol. The provision of both size and boundary on the one hand and bit size and bitbdry on the other allows for both unpacked and packed data representations. A type referent is either a pointer to or the name of a structure representing a constructed type (in ican, lacking pointers, we would use the latter). The provision of type, basetype, and machtype allows us to specify, for example, that the Pascal type array [1..3,1..5] of char has for its type field a type referent such as t2, whose

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