HLASM: V1R6 Language Ref

Terms, literals, and expressions┌───────────┐│││Absolute ││Expression │││└─────┬─────┘│ Can be any of├─────────────┬─────────────┬─────────────┬─────────────┬─────────────┬─────────────┬─────────────┬─────────────┐│ │ │ │ │ │ │ │ │ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐│ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ ││ Rel. Exp. │ │ Absolute │ │ Abs. Exp. │ │ Abs. Exp. │ │ Abs. Exp. │ │ Abs. Exp. │ │(Abs. Exp.)│ │ +Abs. Exp.│ │ −Abs. Exp.││ − │ │ Term │ │ + │ │ − │ │ * │ │ / │ │ │ │ │ │ ││ Rel. Exp. │ │ │ │ Abs. Exp. │ │ Abs. Exp. │ │ Abs. Exp. │ │ Abs. Exp. │ │ │ │ │ │ │ │ │└─────┬─────┘ └─────┬─────┘ └───────────┘ └───────────┘ └───────────┘ └───────────┘ └───────────┘ └─┼─────────┘ └─┼─────────┘│ │ └──────┬──────┘│ Can be any of ││ ├─────────────┬─────────────┬─────────────┬─────────────┐ unary operators│ │ │ │ │ ││ │ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐│ │Absolute │ │ Self- │ │ Symbol │ │ Symbol │ │ Symbol ││ │Valued │ │ Defining │ │ Length │ │ Integer │ │ Scale ││ │Ordinary │ │ Term │ │ Attribute │ │ Attribute │ │ Attribute ││ │Symbol │ │ │ │ │ │ │ │ ││ └───────────┘ └───────────┘ └───────────┘ └───────────┘ └───────────┘│┌─────┴─────┐│││Relocatable││Expression │││└─────┬─────┘│ Can be any of├─────────────┬─────────────┬─────────────┬─────────────┬─────────────┐│ │ │ │ │ │ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ ┌─────┴─────┐ Operators Allowed│ │ │ │ │ │ │ │ │ │ │ ││Relocatable│ │ Rel. Exp. │ │ Rel. Exp. │ │(Rel. Exp.)│ │+Rel. Exp. │ │−Rel. Exp. │ Unary: + Positive│Term │ │ + │ │ − │ │ │ │ │ │ │ − Negative│ │ │ Abs. Exp. │ │ Abs. Exp. │ │ │ ││ │ ││ │└─────┬─────┘ └───────────┘ └───────────┘ └───────────┘ └┼──────────┘ └┼──────────┘ Binary: + Addition│ │ │ − Subtraction│ └──────┬──────┘ * Multiplication Can be any of │ / Division├─────────────┐ unary operators││┌─────┴─────┐ ┌─────┴─────┐│Relocatable│ │ Location │ Rel. Exp. = Relocatable Expression│Valued │ │ Counter │ Abs. Exp. = Absolute Expression│Ordinary │ │ Reference ││Symbol │ │ │└───────────┘ └───────────┘Figure 11. Definitions of absolute and relocatable expressionsEvaluation of expressionsA single-term expression, like 29 or BETA, has the value of the term involved. Theassembler reduces a multiterm expression, like 25*10+A/B or BETA+10, to a singlevalue, as follows:1. It evaluates each term.2. It does arithmetic operations from left to right. However:a. It does unary operations before binary operations.b. It does binary operations of multiplication and division before the binaryoperations of addition and subtraction.3. In division, it gives an integer result; any fractional portion is dropped.Division by zero gives 0.Chapter 2. Coding and structure 45