HLASM: V1R6 Language Ref

DS instructionv An ordinary symbolv A variable symbol that has been assigned a character string with a value thatis valid for an ordinary symbolv A sequence symbolIf symbol denotes an ordinary symbol, the ordinary symbol represents theaddress of the first byte of the storage area reserved. If several operands arespecified, the first storage area defined is addressable by the ordinary symbol.The other storage areas can be reached by relative addressing.operandis an operand of six subfields. The first five subfields describe the attributes ofthe symbol. The sixth subfield provides the nominal values that determine theimplicit lengths; however no constants are generated.A DS operand has this format:►►duplication_factortypetype_extensionprogram_type►►modifiernominal_value►◄The format of the DS operand is identical to that of the DC operand; exactly thesame subfields are used and are written in exactly the same sequence as they arein the DC operand. For more information about the subfields of the DCinstruction, see “DC instruction” on page 125.Unlike the DC instruction, the DS instruction causes no data to be assembled.Therefore, you do not have to specify the nominal value (sixth subfield) of a DSinstruction operand. The DS instruction is the best way of symbolically definingstorage for work areas, input/output buffers, etc.Although the formats are identical, there are two differences in the specification ofsubfields. They are:v The nominal value subfield is optional in a DS operand, but it is mandatory in aDC operand. If a nominal value is specified in a DS operand, it must be valid.v The maximum length that can be specified for the character (C) and hexadecimal(X) type areas is 65,535 bytes rather than 256 bytes for the same DC operands.The maximum length for the graphic (G) type is 65,534 bytes.If symbol denotes an ordinary symbol, the ordinary symbol, as with the DCinstruction:v Has an address value of the first byte of the area reserved, after any boundaryalignment is donev Has a length attribute value, depending on the implicit or explicit length of thetype of area reservedIf the DS instruction is specified with more than one operand or more than onenominal value in the operand, the label addresses the area reserved for the field174 HLASM: V1R6 Language Ref