<processor> A register found in some CPUs, whose contents
can be added to the address operand to give the effective
address. Incrementing the index register then allows the
program to access the next location in memory and so on,
making it very useful for working with arrays or blocks of
memory.
Index registers first appeared around April 1949 in the
Manchester Mark I. The Mark I's index register's contents
were simply added to the entire instruction, thus potentially
changing the opcode (see The story of Mel)!
(2006-09-20)
Nearby terms:
index « Index Data « Indexed Sequential Access Method « index register » indices » indirect address » indirect addressing
