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An odd offset would cause a program check (unless the base register itself also contained an odd address)—since instructions had to be aligned on half-word boundaries to execute without a program or hardware interrupt. The previous example describes an indirect way to address to a memory location in the format of segment:offset.
where "disp" is the displacement specified by the "mod" bits. As a special exception, the combination mod=00 2, r/m=110 2, which would normally specify [BP + disp0], instead specifies a 16-bit address [disp16] with no register base at all. To address [BP+0], one must use a 1-byte displacement ("disp8") form with a displacement of 0.
In computing, a base address is an address serving as a reference point ("base") for other addresses. Related addresses can be accessed using an addressing scheme.. Under the relative addressing scheme, to obtain an absolute address, the relevant base address is taken and an offset (aka displacement) is added to it.
Direct address: ADD.A address 1 — add the value stored at address 1; Memory indirect: ADD.M address 1 — read the value in address 1, use that value as another address and add that value; Many ISAs also have registers that can be used for addressing as well as math tasks. This can be used in a one-address format if a single address register ...
Some security experts feel that including the "Discoverability" element as the last D rewards security through obscurity, so some organizations have either moved to a DREAD-D "DREAD minus D" scale (which omits Discoverability) or always assume that Discoverability is at its maximum rating.
Load Program Status Word (LPSW) is a privileged instruction that loads the Program Status Word (PSW), including the program mode, protection key, and the address of the next instruction to be executed. LPSW is most often used to "return" from an interruption by loading the "old" PSW which is associated with the interruption class.
The Information Technology Security Evaluation Criteria (ITSEC) is a structured set of criteria for evaluating computer security within products and systems. The ITSEC was first published in May 1990 in France , Germany , the Netherlands , and the United Kingdom based on existing work in their respective countries.
Computer architectures vary greatly as to the number of addressing modes they provide in hardware. There are some benefits to eliminating complex addressing modes and using only one or a few simpler addressing modes, even though it requires a few extra instructions, and perhaps an extra register.