Like all Motorola processors that share lineage from the accumulator A, a 16-bit index register H : X, a 16-bit stack pointer SP, a 16-bit program counter PC, and an 8-bit condition code register CCR . Some instructions refer to the different bytes in the H : X index register independently.
32.
The 8 bit EC register contains condition codes bits . ( Some of this is illustrated in the much simpler instruction set of the GEC 2050 . ) A read-only " keys " register allows programs to read the value set on the front panel toggle switches ( keys ) by the operations staff.
33.
This is a small selection of some early lost or notable asteroids with their discovery and rediscovery dates . " ( A more detailed description for some of these minor planets can be found in the condition code of U & thinsp; = & thinsp; 9, indicating the highest possible uncertainty of their orbit determination.
34.
When entering Monitor it shows a prompt on the first line, " Trap ! " on the second line ( if entered via a trap ) and the CPU Accumulator A ), B ( Accumulator B ), X ( Index Register ), C ( Condition Code Register ), S ( Stack Pointer ) and P ( Program Counter ).
35.
Conditional branch instructions test this encoded as a values from 0 to 15, representing the arithmetic sum of the four condition code values, 2 3 + 2 2 + 2 1 + 2 0 . ( Since IBM uses big-endian bit numbering, mask value 8 selects code 0, mask value 4 selects code 1, mask value 2 selects code 2, and mask value 1 selects code 3 .)
