1940S—Vacuum Tubes

Vacuum tubes are used to control the flow of electrons. Since vacuum tubes responded faster than mechanical components, faster computations were possible. But, the tubes consumed a lot of power and burned out quickly.

Below is a picture of vacuum tubes.

Figure 3 Vacuum tubes

1945: The first computer prototype using vacuum tubes, ENIAC (Electronic Numerical Integrator and Computer) was designed to calculate trajectory tables for the U.S. Army during World War II, but it was not completed until three months after the war.

The machine was 100 feet long and 10 feet high and weighed 30 tons. It had over 18,000 vacuum tubes. But, in the first year, a total of 19,000 tubes burned out and were replaced. The ENIAC could perform 5,000 additions per second, but its operation has to be programmed manually by connecting cables and setting 6,000 switches.

The first commercially successful computer, UNIVAC was developed by Eckert-Mauchly Computer Corporation (later acquired by Remington Rand). The machine was 14.5 feet long, 7.5 feet high, and 9 feet wide. It could read 7,200 characters per second. It was priced at $930,000. Another important development was the invention of the compiler by Admiral Grace Hopper who was working at Eckert-Mauchly Computer Corporation at the time. A compiler enables program instructions to be written in English and then translated into a language that the machine can understand. This invention made the task of programming easier and faster.

1950S—Transistors

Transistors performed functions similar to vacuum tubes but they were smaller, cheaper, and more reliable. Additionally, they consumed less power. The ability for transistors to replace vacuum tubes was first demonstrated in AT&T’s Bell Laboratories. Transistor-based computers could perform 200,000 to 250,000 calculations per second.

Transistors are also used in other electrical devices such as the radio. Below is a picture of a radio and transistors.

Figure 4 Transistors

1960S—Integrated Circuits

An integrated circuit, also called a "microchip" or "chip," is a thin slice of silicon packed with microscopic circuit elements such as wires, transistors, capacitors, and resistors. It was developed in 1958 by Jack Kilby at Texas Instruments and independently by Robert Noyce at Fairchild Semiconductor. Integrated circuits enabled the equivalent of thousands of vacuum tubes or transistors to be packed onto a single miniature chip about the size of your fingernail, reducing the physical size, weight, and power requirements for devices such as computers. Computers became ever smaller as more components could fit onto the chip. More information about the IC chip can be found at the Smithsonian Institute's Jerome and Dorothy Lemelson Center for the Study of Invention and Innovation.

1970S to Present—Microprocessor

The microprocessor combined components of a computer on a microchip. Before the microprocessor was developed, each integrated circuit had to be manufactured for a particular purpose, but now a microprocessor can be manufactured and then programmed for various purposes to other needs. Below is a picture of a microprocessor. Note that millions of wires are etched onto an area the size of a fingernail.

Figure 6 Microprocessor chip

The first general-purpose microprocessor was the Intel 4004. It was developed in 1971 by Ted Hoff. The Intel 4004 enabled microprocessor-based computer systems to become faster, smaller, and less expensive than before.

Pace of Advancement

Transistors are still continuing to decrease in size. As transistors become smaller, more transistors can be placed on a given chip. This implies faster processing speeds and greater data storage capacity. In 1965, Gordon Moore, a founder of Intel, one of the largest microchip manufacturers, made his observation that there is an exponential growth in the number of transistors per integrated circuit. He predicted that the number of transistors that can be put on a microchip will double every 12 months, until physical limitations are reached. This observation was termed "Moore’s Law." Now the exponential growth has slowed down to doubling every 18 months, nevertheless, the rate of growth is still exponential. More about Moore’s Law will be explained in page 2.5.1 Moore’s Law. The chart below shows the rate of growth for number of transistors on microchips.

	Year of Introduction	Transistors
4004	1971	2,250
8008	1972	2,500
8080	1974	5,000
8086	1978	29,000
286	1982	120,000
386TM processor	1985	275,000
486TM DX processor	1989	1,180,000
Pentium® processor	1993	3,100,000
Pentium II processor	1997	7,500,000
Pentium III processor	1999	24,000,000
Pentium 4 processor	2000	42,000,000
Itanium 2 processor	2002	220,000,000
Pentium D	2006	376,000,000
Core i7	2008	781,000,000

Table 1 Number of transistors used in Intel processors over the years [Intel Research Site]