Features of a computer

1. 
   
   speed, size and cost

The speed of a computer is linked to the technology used to build it. ENIAC was built suing vacuum tubes. With this technology, speed was measured in milliseconds. It could add two numbers in 0.2 milliseconds and multiply them in 3 milliseconds. In other words, it could perform 5000 additions or 300 multiplications per second. It occupied an area of about 150 square meters and cost millions of dollars. It was not very reliable, developing faults (because of blown vacuum tubes)several times per hour.

After the invention of the transistor in 1947, computers were built using transistors replacing vacuum tubes. This decreased the size of the cokputer and increased its operation speed. Speeds were then measured in microseconds. They could perform million additions per second. The price was reduced beceuse of improvement in the technology. In around 1958-1959 integrated circuit (IC) was developed. In a single IC chip, a number of electronic components such as transistors and diodes can be fabricated(made). The typical size of an IC chip is roughly 0.25 square cm (0.5 cm x0.5 cm). So, after the invention of the IC technology, transistors were replaced by ICs in building a computer. The computers developed with ICs were smaller. The use of IC in a cokputer inceased the speed to tens of millions of operations per second.