The following material is from the

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Historical Computers

• The following material is from the
• Computer History Museum
• http//www.computerhistory.org

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1944-Harvard Mark-1 Conceived by Harvard
professor Howard Aiken, and designed and built by
IBM, the Harvard Mark-1 was a room-sized,
relay-based calculator. The machine had a
fifty-foot long camshaft that synchronized the
machines thousands of component parts. The
Mark-1 was used to produce mathematical tables
but was soon superseded by stored program
computers.
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1946-February, the public got its first glimpse
of the ENIAC, a machine built by John Mauchly and
J. Presper Eckert that improved by 1,000 times on
the speed of its contemporaries. Start of
project 1943Completed 1946Programmedplug board
and switches Speed5,000 operations per
second Input/outputcards, lights, switches,
plugs Floor space1,000 square feet Project
leadersJohn Mauchly and J. Presper Eckert.
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Punch CardsThe IBM card format, designed in
1928, had rectangular holes, 80 columns with 12
punch locations each, one character to each
column. Card size was exactly 187.325 by 82.55
mm. The top two positions of a column were
called zone punches, 12 (top) and 11. These often
encoded plus and minus signs. The lower ten
positions represented (from top to bottom) the
digits 0 through 9. Originally only numeric
information was coded, with 1 or 2 punches per
column digits (digit 0-9) and signs (zone
12,11 ). Later, codes were introduced for
upper-case letters and special characters. A
column with 2 punches (zone 12,11,0 digit
1-9) was a letter 3 punches (zone 12,11,0
digit 2-4 8) was a special character.
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IBM Keypunch Machine 026
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1950 Early computers were limited because there
was no way to build reliable and high-speed
memory memory. Magnetic core solved these
problems and subsequently became the dominant
form of computer memory for more than 20 years.
Core memory uses a 3-dimensional array of tiny
ferrite rings to store data or programs. Each
ring stores a single bit and is magnetized in
either a clockwise or counterclockwise direction,
representing a 0 or a 1 respectively. The
cores are magnetized by a current flowing in
wires that are threaded through each core. The
direction of the current determines the direction
of the magnetization
In 1953, Jay Forrester invented coincident
current addressing, which made core memory
practical. In this scheme, the current needed
to magnetize the core is split between two wires
(one horizontal, the other vertical). Only the
core at the intersection of two electrified wires
will change magnetization. In order to read a
single core, a third wire is threaded through all
the cores of a plane. When a core is magnetized
to a 0, a pulse occurs on this sense wire only
if that core had been a 1 and not if it was
already a 0. This is destructive readout, since
if it was a 1 it now needs to be rewritten.
Consequently, it takes two cycles to read core
memory, one to read the contents and another to
reset it to its original state.
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1951-The UNIVAC I delivered to the U.S. Census
Bureau was the first commercial computer to
attract widespread public attention. Although
manufactured by Remington Rand, the machine often
was mistakenly referred to as the "IBM UNIVAC."
Remington Rand eventually sold 46 machines at
more than 1 million each.F.O.B. factory 750,000
plus 185,000 for a high speed printer.
Speed1,905 operations per second Input/outputmag
netic tape, unityper, printer Memory size1,000
12-digit words in delay lines Memory typedelay
lines, magnetic tape Technologyserial vacuum
tubes, delay lines, magnetic tape Floor space943
cubic feet CostF.O.B. factory 750,000 plus
185,000 for a high speed printer Project
leadersJ. Presper Eckert and John Mauchly
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1961-IBM 1301 Disk Storage Unit is released. The
IBM 1301 Disk Drive was announced on June 2nd,
1961 for use with IBMs 7000-series of mainframe
computers. Maximum capacity was 28 million
characters and the disks rotated at 1,800 R.P.M.
The 1301 leased for 2,100 per month or could be
purchased for 115,500. The drive had one
read/write arm for each disk as well as flying
heads, both of which are still used in todays
disk drives.
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1962 - IBM 1311 Disk Storage Drive is announced.
Announced on October 11, 1962, the IBM 1311 was
the first disk drive IBM made with a removable
disk pack. Each pack weighed about ten pounds,
held six disks, and had a capacity of 2 million
characters. The disks would rotate at 1,500 RPM
and were accessed by a hydraulic actuator with
one head per disk. The 1311 offered some of the
advantages of both tapes and disks.
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1963 - ASCII American Standard Code for
Information Interchange permitted machines from
different manufacturers to exchange data. ASCII
consists of 128 unique strings of ones and zeros.
Each sequence represents a letter of the English
alphabet, an Arabic numeral, an assortment of
punctuation marks and symbols, or a function such
as a carriage return.
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Transistors and Transistor based circuit boards
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1964 - IBM announced the System/360, a family of
six mutually compatible computers and 40
peripherals that could work together. The
initial investment of 5 billion was quickly
returned as orders for the system climbed to
1,000 per month within two years. At the time
IBM released the System/360, the company was
making a transition from discrete transistors to
integrated circuits, and its major source of
revenue moved from punched-card equipment to
electronic computer systems
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1966 - Hewlett-Packard entered the general
purpose computer business with its HP-2115 for
computation, offering a computational power
formerly found only in much larger computers. It
supported a wide variety of languages, among them
BASIC, ALGOL, and FORTRAN.
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Magnetic DrumsDeveloped in the 1950s, magnetic
drums were the first mechanical direct access
storage devices. Typically, drums were made of a
nickel-cobalt substrate coated with powdered
iron. Data was recorded by magnetizing small
surface regions organized into long tracks of
bits. Unlike tape, data could be accessed
randomly without having to skip large sections of
unwanted information. Prior to the development of
magnetic core memory, drums were used as main
memory for several low cost computers such as the
IBM 650, LGP-30 and Bendix G-15.
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Magnetic TapesMagnetic tape has been used to
store digital information since at least 1951
when Presper Eckert and John Mauchly used it in
the UNIVAC I computer. Their tape was made of
metal, but later tapes have been made mostly of
plastic. Some users of punched cards were
initially reluctant to use tape because they
could no longer see their data. IBMs invention
of the vacuum channel tape drive and improved
magnetic materials resulted in reliable
large-capacity tapes, which even reluctant
customers eventually adopted. Tape data formats
vary widely, and bit density has increased
dramatically. Tape has now been largely replaced
by hard disks for secondary storage, but it is
still used for backing up of data.
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Magnetic Disks In the 1950s, engineers attempted
to develop a device that would provide efficient
secondary storage, but also, unlike tape drives,
provide random access to data. IBM succeeded by
inventing the magnetic disk at their San Jose
laboratories in 1956. Developed as part of a
larger system known as RAMAC, the first Model 350
disk drive contained 50 24-inch diameter disks
and stored a total of five megabytes. IBM later
added removable disk platters to its drives as
featured on the IBM 1311. These platters provided
archival data storage. IBM also was the first
to hermetically seal both platters and read/write
heads in a single enclosure in its Model 3340
Winchester disk drive. Today, all disk drive
manufacturers employ this design convention. A
sampling of the wide variety of disk shapes and
sizes can be seen here.
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1972 PDP 11/40 Minicomputer DEC developed the
PDP-11 as a family of 16-bit minicomputers that
could grow with customers as their computing
needs increased. From the first PDP- 11/20 in
1970 through the PDP-11/94 in 1990, DEC produced
a variety of compatible machines and sold over
500,000. Much like the 12-bit PDP-8 before it,
DEC further integrated the PDP-11 family until in
1982 it had placed one of its largest models, the
PDP-11/70, on two large-scale integrated
circuits. Since the PDP-8 and PDP-11 systems
were subject to export restrictions, Soviet bloc
computer companies commonly cloned the systems
and packaged them under different names. Memory
TypeCore Speed1.25 MHz Memory
Size56K Cost20,000 Memory Width(16-bit)
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1977 - The Commodore PET (Personal Electronic
Transactor) the first of several personal
computers released in 1977 came fully assembled
and was straightforward to operate, with either 4
or 8 kilobytes of memory, two built-in cassette
drives, and a membrane "chiclet" keyboard.
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1977 - The Apple II became an instant success
when released in 1977 with its printed circuit
motherboard, switching power supply, keyboard,
case assembly, manual, game paddles, A/C
powercord, and cassette tape with the computer
game "Breakout." When hooked up to a color
television set, the Apple II produced brilliant
color graphics.
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1981- IBM Personal Computer Although IBMs first
personal computer arrived nearly ten years after
others were available, the IBM Personal Computer
(PC) instantly legitimized and expanded the
market. Unlike most other contemporary IBM
products, the PC incorporated both hardware (the
Intel 8088 microprocessor) and software made by
other companies. IBM published design details in
their manuals that encouraged others to make
copies or clones of the original machine, often
with improved functionality. The IBM PC
architecture quickly became an industry standard.
Memory TypeSemiconductor Speed4.77 MHz Memory
Size16K Cost1,565 Memory Width(8-bit)
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1982 -Commodore introduces the Commodore 64. The
C64, as it was better known, sold for 595, came
with 64KB of RAM and featured impressive
graphics. Thousands of software titles were
released over the lifespan of the C64. By the
time the C64 was discontinued in 1993, it had
sold more than 22 million units and is recognized
by the 2006 Guinness Book of World Records as the
greatest selling single computer model of all
time.