MIT PDP-10 'Info' file converted to Hypertext 'html' format by Henry Baker

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Shift instructions

The following instructions shift or rotate the AC or the double word formed by AC and AC+1.

Shift instructions are all immediate instructions. The effective address is not used as the ddress of a memory operand. Instead, it is used as the number of places to shift. A positive number means a left shift; a negative number (bit 18 = 1) means a right shift.

Aside from the sign bit of the effective address, only the lowest eight bits are used. The other nine bits are ignored.

;Suppose that each bit in accumlator 1 is a flag
;telling us that some sort of processing needs to be done.
;We would like to find out which flags are set
;and, for each one, do the processing.  But we don't want to
;waste a lot of time checking flags which are not set.

        ...                     ;Here all flags are zero.

TABLE:  FOO                     ;FOO handles flag bit 0
        BAR                     ;BAR handles flag bit 1.
        ...                     ;Other addresses for the remaining

FOO:    ...                     ;Do the work.
        TLZ 1,400000            ;Clear flag bit 0
        JRST LOOP               ;Find the next flag which is set.