Wikipedia

IBM Basic assembly language and successors: Difference between revisions

Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
→Assembler instructions: relative addresses; DROP
→Assembler instructions: Capital letters at the beginning of a sentence, but not at the beginning of clauses not at the beginning of the sentence.
Line 103:
USING base,reg-1,...,reg-n
</syntaxhighlight>
Machine instruction addresses on S/360 specify a ''displacement'' (0–4095 bytes) from the value in a ''base register''; Whilewhile later versions of the architecture added relative-address formats, the older formats are still used by many instructions. <code>USING</code> allows the programmer to tell the assembler that the specified base registers are assumed to contain the address of "base", base+4096 (if multiple registers are specified), etc. This only provides a shortcut for the programmer, who otherwise would have to specify the base register in each instruction. Programmers are still responsible for actually loading the address of "base" into the register before writing code that depends on this value.
 
The related <code>DROP</code> assembler instruction nullifies a previous <code>USING</code>.
Retrieved from "https://en.wikipedia.org/wiki/IBM_Basic_assembly_language_and_successors"