1. <computer> 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.
