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Some kinds of value are common to most Programming Language s (e.g., various kinds of number representations), while others are less commonly supported (e.g., Pascal supports a set type). IN C: L-VALUE AND R-VALUE Some languages use the idea of L-value and '''R-value'''. L-values are values that have Addresses , meaning they are variables or dereferenced references to a certain place. R-value is either L-value or non-L-value — a term only used to distinguish from L-value. In C, the term l-value originally meant something that could be assigned (coming from left-value, indicating it was on the left side of the = operator), but since 'const' was added to the language, this now is termed a 'modifiable L-value'. An L-value is an expression that designates (refers to) an object. A non-modifiable L-value is addressable, but not assignable. A modifiable L-value allows the designated object to be changed as well as examined. An R-value is any expression that is not an L-value, it refers to a data value that is stored at some address in memory. IN ASSEMBLY LANGUAGE A value can be virtually any kind of data by a given data type, for instance a string, a digit, a single letter. In assembly language there is something known as "immediate value", sometimes "immediate" for short; The value comes with the instruction; occasionally it can be written as "imm#" where # is a number indicating the size of the immediate value, so imm8 would refer to an immediate byte size value. An immediate value is a number, either written with digits or as a string" "mnemonic 'A'" could be the same as "mnemonic 0x64"; the Byte Order of strings differs depending on the assembler and architecture. EXTERNAL LINKS |
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