IAS
The first modern computer. It had main
{registers}, processing circuits, information paths within the
{central processing unit} and used {Von Neumann}'s
{fetch-execute cycle}.
The IAS machine's basic unit of information was a 40 bit
{word} and the memory had 4096 words. A word stored in memory
could represent either an instruction or data. Each IAS
instruction was twenty bits long, so that two instructions
could be stored in each 40-bit memory location. Each
instruction consisted of an 8-bit {operation code} and a
12-bit address that could identify any of 2^12 locations that
may be used to store an {operand} of the instruction.
The {CPU} consisted of a data processing unit and a program
control unit. It contained various processing and control
circuits along with a set of high-speed {registers} for the
temporary storage of instructions, memory addresses and data.
The main actions specified by instructions were performed by
the arithmetic-logic circuits of the data processing unit. An
electronic clock circuit was used to generate the signals
needed to synchronise the operation of the different parts of
the system.
(1996-11-24)