The first generation of computers used vacuum tubes, magnetic drums for storage, and were hardwired to perform specific calculations. They were very large, unreliable, and produced significant heat. Programming involved manipulating toggle switches to input programs in machine language. The introduction of transistors in the late 1940s led to more reliable, portable, and faster computers by replacing vacuum tubes. This allowed computing to advance from specialized machines to general purpose computers.

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3.  Generally, the computers built during the World War II era are known
as the first generation computers. These are considered the first
computers, and were extremely different from the computers we see
today. Because the first generation computers were extremely difficult
to program, they were designed for a specific task, and they never made
it to the general market. These primitive computers relied on vacuum
tubes and magnetic drums.

4.  A sealed glass tube containing a near-vacuum that
allows the free passage of electric current.

5.  magnetic drums were easily adaptable for data storage - the drum's
surface was coated with a ferromagnetic material that could store
digital data by changing the magnetic properties of the material
(similar to the way in which data is stored on a hard disk today). Most
computers built between 1950 and 1955 used drum memory.

6.  Early computers had no input devices, or any type of software as we
know it today. They were "hard-wired" to perform specific
mathematical calculations - a computer's function could only be
changed by re-wiring its circuits.
 By the time the UNIVAC appeared in 1951, a control panel on the front
of the computer allowed simple input through a series of toggle
switches and buttons. The toggles were used to input the first
computer programs and data - in binary format!

7.  The programming was very limited and very complex USN machine
language. Usually they were hardwired and the applications very
limited.
 One of the problems with vacuum tubes was that they took up a large
amount of space. The ENIAC, developed in 1946, used 18,000 vacuum
tubes, weighed 30 tons and covered 1,800 square feet! The vacuum
tubes also produced a lot of heat, so that even with giant air-conditioning
systems, the vacuum tubes would burn out regularly and
need to be replaced.

8.  This is a small vacuum tube, used in first generation
computers. Here you can clearly see the effect of
overheating, leaving a black stain on the inside of the
glass tube. Constant overheating and burnout in the
vacuum tubes of ENIAC.
 First generation computers relied on machine
language, the lowest-level programming language
understood by computers, to perform operations, and
they could only solve one problem at a time.

9.  Vacuum tube technology made possible the development
of electronic digital computers.
 Magnetic tapes and drums were used as secondary memory

10.  1939-1942: Atanasoff-Barry Computer - John Atanasoff and Clifford Berry
 1941: Z3 – Konrad Zuse
 1943: Colossus - Tommy Flowers and Max Newman
 1944: Harvard Mark I - Howard Aiken
 1943-1946: ENIAC - Dr. John Mauchly and J. Presper Eckert
 1945: EDVAC - Jogh Mauchly and J. Preper Eckert
 1944-1945: Plankalkul - Plankalkul
 1947: Transistors - Bell Telephone laboratories.
 1948: SSEC - IBM
 1949: EDSAC - Maurice Wilkes
 1945-1951: Whirlwind - Jay Forrester and Robert Everrett
 1951: UNIVAC - John Mauchley and J. Presper Eckert Junior
 1953: IBM 701 - IBM
 1954: IBM 650 - IBM

11. More Reliability
 Better Portability
 Less Heat Generation
 Smaller size
 Faster Computers

12.  Very small size compared to a vacuum tube for the same amount of
amplification.
 No warm-up time. A tube takes 30 seconds to warm up.
 A transistor is very easy to mass produce compared to a tube.
 A transistor can take extreme amounts of shock and vibration
compared to a tube.
 A transistor is usually much lower in cost compared to a tube that
gives the same amplification.
 Transistors generally live and work forever whereas tubes burn out after
a while