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IanBland · 30th Jul 2017, 5:04 pm

The USR function returns the contents of the BC register pair. It was a useful if crude means of communicating a result back from a machine code routine to BASIC.

30th Jul 2017, 5:04 pm	#28
IanBland Hexode Join Date: May 2015 Location: Northampton, Northants, UK. Posts: 380	Re: Sinclair ZX81 The USR function returns the contents of the BC register pair. It was a useful if crude means of communicating a result back from a machine code routine to BASIC.