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Legac-e - Assembler for non-Assembler Programmers
Decision making
Decision making in Assembler is based on the setting of a 2-bit Condition Code (CC, bits 18 & 19) and always requires two
instructions, the first to set the code, and the second, a Branch which tests the Condition Code and routes execution
accordingly.
The two bits give four possible settings in binary; '00', '01', '10', and '11', so the Branch has a 4-bit mask for the test.
(A mask of '1111' indicates an unconditional Branch (GOTO.)
Not all instructions set the Condition Code, but equally is it not restricted to Compares.
See some examples
The process is equivalent to COBOL and PLI IF statements.