second generation computer

architecture A computer built from transistors, designed

between the mid-1950s and mid-1960s.

Ferrite core memory and magnetic drums replaced cathoderay tubes and delay-line storage for main memory. Indexregisters and floating point arithmetic hardware became

widespread. Machine-independent high level programminglanguages such as ALGOL, COBOL and Fortran were

introduced to simplify programming.

I/O processors were introduced to supervise input-output

operations independently of the CPU thus freeing the CPU

from time-consuming housekeeping functions. The CPU would

send the I/O processor an initial instruction to start

operating and the I/O processor would then continue

independently of the CPU. When completed, or in the event of

an error, the I/O processor sent an interrupt to the CPU.

Batch processing became feasible with the improvement in I/O

and storage technology in that a batch of jobs could be

prepared in advance, stored on magnetic tape and processed on

the computer in one continuous operation placing the results

on another magnetic tape. It became commonplace for

auxiliary, small computers to be used to process the input and

output tapes off-line thus leaving the main computer free to

process user programs. Computer manufacturers began to

provide system software such as compilers, subroutine

libraries and batch monitors.

With the advent of second generation computers it became

necessary to talk about computer systems, since the number of

memory units, processors, I/O devices, and other system

components could vary between different installations, even

though the same basic computer was used.

The instruction repertoire of the IBM 7094 (a typical second

generation machine) had over 200 instructions including data

transfer instructions for transferring a word of information

between the CPU and memory or between two CPU registers;

fixed-point and floating point arithmetic instructions;

logic instructions (AND, OR etc.); instructions for

modifying index registers; conditional and unconditional

branching; subroutines; input-output operations for

transferring data between I/O devices and main memory.

(1996-11-25)