??? The basic operational loop of the computer is to read
the instruction stored in the memory location pointed to by the P register, increment the P register, execute the
instruction found in memory, and repeat.
An early improvement in programming productivity was the assembler. An assembler can read mnemonics
(letters and numbers) for the machine instructions, and for each mnemonic generate the machine language
in ones and zeros.
Assembly languages are called second-generation languages. With assembly language programming, the
programmer can work in the world of letters and words rather than ones and zeros. Programmers write their code
using the mnemonic codes that translate directly into machine instructions. These are typical of such mnemonics:
LDA m Load the A-register from memory location m.
ADA m Add the contents of memory location m to the contents of the A-register, and leave
the sum in the A-register.
ALS A Left Shift; shift the bits in the A-register left 1 bit, and make the least significant bit zero.
SSA Skip on Sign of A; if the most significant bit in the A-register is 1, skip the next
instruction, otherwise execute the next instruction.
JMP m Jump to address m for the next instruction.
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