As mentioned previously, one of the

As mentioned previously, one of the most important characteristics of a computer is its capability of storing information in its memory long enough to process it. Not all computers have the same type of memory. In this section, three types of memory will be discussed, core memory, semiconductor memory (or chip), and bubble memory.
The memory of the first computers was made of a kind of grid of fine vertical and horizontal wires. At each intersection where the wires crossed, there was a small ferrite ring called a core (hence the name “core memory”) which was capable of being either magnetized or demagnetized. Every intersection had its unique address, consequently, when an electrical current was passed through the wires, the magnetized as well as the unmagnetized cores were identified by their respective addresses. Each core represented a binary digit of either 0 or 1, depending on its state. Early computers had a capacity of around 80.000 bits; whereas now, it is surprising to hear about computers with a memory capacity of millions of bits. This has been made possible by the advent of transistors and by the advances in the manufacture of miniaturized circuitry. As the result, mainframes have been reduced in both size and cost. Throughout the 1950s, 1960s and up to the mid-1970s, core memory dominated the market.
In the 1970s, there was a further development which revolutionized the computer field. This was the ability to etch thousands of integrated circuits onto a tiny piece (chip) of silicon, which is a non-metallic element with semiconductor characteristics. Chips have thousands of identical circuits, each one capable of storing one bit. Because of the very small size of the chip, and consequently of the circuits etched on it, electronical signs do not have to travel far; hence, they are transmitted faster. Moreover, the size of the components containing the circuitry can be considerably reduced, a step which has led to the introduction of both minis and micro. As a result, computers have become smaller, faster, and cheaper. There is one problem with semiconductor memory, however: when power is removed, information in the memory is lost- unlike core memory, which is capable of retaining information during a power failure.
Another development in the field of computer memories is bubble memory. The concept consists of creating a thin film of metallic alloys over the memory board. When this film is magnetized, it produces magnetic bubbles, the presence, or absence of which represents one bit of information. These bubbles are extremely tiny, about 0.1 micrometer in diameter. Therefore, a magnetic bubble can store information at a greater density than existing memories, which makes it suitable for micros. Bubble memories are not expensive, consume little power, are small in size, and are highly reliable. There is probably a lot more to learn about them, and research in this field continues.