Instruction Set
The PDP-11 operates on bytes and words. Bytes are specified by a register number—identifying the register's low-order byte—or by a memory location. Words are specified by a register number or by the memory location of the low-order byte, which must be an even number. In most instructions that take operands, bit 15 is set to specify byte addressing, or clear to specify word addressing. In the lists in the following two sections, the assembly-language programmer appended B to the instruction symbol to specify a byte operation; for example, MOV became MOVB.
Read more about this topic: PDP-11 Architecture
Famous quotes containing the words instruction and/or set:
“A little instruction in the elements of chartography—a little practice in the use of the compass and the spirit level, a topographical map of the town common, an excursion with a road map—would have given me a fat round earth in place of my paper ghost.”
—Mary Antin (1881–1949)
“To find the length of an object, we have to perform certain
physical operations. The concept of length is therefore fixed when the operations by which length is measured are fixed: that is, the concept of length involves as much as and nothing more than the set of operations by which length is determined.”
—Percy W. Bridgman (1882–1961)