HLASM: V1R6 Language Ref

Statement formatsSymbolic operation codesWhen you code machine instructions, you use symbolic formats that correspond tothe actual machine language formats. Within each basic format, you can also codevariations of the symbolic representation, divided into groups according to thebasic formats shown below.The assembler converts only the operation code and the operand entries of theassembler language statement into object code. The assembler assigns to a nameentry symbol the value of the address of the first byte of the assembled instruction.When you use this same symbol in the operand of an assembler languagestatement, the assembler uses this address value in converting the symbolicoperand into its object code form. The length attribute assigned to the symboldepends on the basic machine language format of the instruction in which thesymbol appears as a name entry.A remarks entry is not converted into object code.An example of a typical assembler language statement follows:LABEL L 4,256(5,10) LOAD INTO REG4where:LABEL is the name entryL is the operation code mnemonic (converted to hex 58)4 is the register operand (converted to hex 4)256(5,10) are the storage operand entries (converted to hex 5A100)LOAD INTO REG4are remarks not converted into object codeThe object code of the assembled instruction, in hexadecimal, is:5845A100 (4 bytes in RX format)You must specify an operation code for each machine instruction statement. Thesymbolic operation code, or mnemonic code as it is also called, indicates the typeof operation to be done; for example, A indicates the addition operation. See theapplicable Principles of Operation manual for a complete list of symbolic operationcodes and the formats of the corresponding machine instructions.The general format of the machine instruction operation code is:Operation code format►►VERBMODIFIER DATA TYPE MACHINE FORMAT►◄Verb The verb must always be present. It usually consists of one or twocharacters and specifies the operation to be done. The verb is underscoredin the following examples:A 3,AREA A indicates an add operationMVC TO,FROM MV indicates a move operationChapter 4. Machine instruction statements 81