The four generations of computers

What are they?

The First Generation (1945-1955)

- Very large computers made up of vacuum tubes and often programmed using wiring plugboards
- Programmed using machine language
- Mostly used for numerical calculations as working out mathematical tables

The Second Generation (1955-1965)

The second generation of computers was an advanced analuoge computer, this was developed in the fist half of the 20th century.

- Mainframes made up of transistors
- Mainframes made up of transistors
- At first punch cards were used to provide input, then tapes were used (for batch processing)
- Used Assemblers and FORTRAN compilers for program writing
-Simple batch processing was used with input files, programs and output on tape
- Smaller computers (e.g. IBM 1401) was used to read programs and data on punch cards on to input tapes and for offline printing
- Used mainly for scientific and engineering applications
- FMS (Fortran Monitor System) and IBM IBSYS as OSs for handling jobs (e.g. to read a job and to run

The Third Generation (1965-1980)

The third generation was the fist generation of computers to be electronic and able to be run more than one programme at the same time.

-Mainframes based on small scale ICs were used.
- Capable of multiprogramming (running several jobs at the same time)
- Fixed disks were used and new jobs on cards to be executed could be read on to the disk while executing other jobs (spooling)
- Though the first models used multiprogrammed batch processing, to cater to increased response time, timesharing was introduced later (Time-sharing Systems)
- Complex OSs as OS/360 were used.
- Used for various applications including scientific and business applications
- Mini computers also appeared on the market which were used by small departments etc. and became the platform for UNIX.

The Fourth Generation (1980-present)

This is the fourth and final generation of computers these have also been developed into phones and PC's, tablets which can be handheld.

- Mainframes, Minicomputers, Workstations, Personal Computers (Desktop and portable) based on VLSI components
- Network operating systems that facilitate file sharing, remote logging etc. and Client Server computing.
- Distributed OSs that make use of multiple machines and processors to run applications.
- GUI based OS interfaces and applications.
- Virtual Machines and Network Computers (NCs)