- Status flags are a key part of most processors, indicating if an arithmetic result is negative, zero, or has a carry, for instance. In this post, I take a close look at the flag circuitry in the Intel 8086 processor (1978), the chip that launched the PC revolution.1 Looking at the silicon die of the 8086 reveals how its flags are implemented. The 8086’s flag circuitry is surprisingly complicated, full of corner cases and special handling. Moreover, I found an undocumented zero register that is used by the microcode.
- Right angle (Wikipedia)
In geometry and trigonometry, a right angle is an angle of exactly 90 degrees or đ/2 radians corresponding to a quarter turn. If a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. The term is a calque of Latin angulus rectus; here rectus means “upright”, referring to the vertical perpendicular to a horizontal base line.