488 private links
Celebrating the world's first minicomputer, and
the machine that taught me assembly language.
The 12-bit PDP-8 contained a single 12-bit accumulator (AC),
a 1-bit "Link" (L), and a 12-bit program counter (PC):
Original photo credit: Gerhard Kreuzer
Later models (the /e, /f, /m & /a) added a 12-bit multiplier quotient (MQ) register.
The term “minicomputer” was not coined to mean miniature, it
was originally meant to mean minimal, which is a term that,
more than anything else, accurately describes the PDP-8.
Whereas today's machines group their binary digits (bits) into sets of four in a system called “hexadecimal”, the PDP-8, like most computers of its era, used “octal” notation, grouping its bits into sets of three. This meant that the PDP-8's 12-bit words were written as four octal digits ranging from 0 through 7.
The first 3 bits of the machine's 12-bit word (its first octal digit) is the operation code (OpCode). This equipped the machine with just eight basic instructions:
