The early computers of Figure 1.3 and others of their time were manufactured using vacuum tubes as electronic switching device. A vacuum tube [see Figure 1.4 (a)] was a fragile glass device using filaments as a source of electronics and could control and amplify electronic signals. It was the only high-speed electronic switching device available in those days. These vacuum tube computers could perform computations in milliseconds and were known as first-generation computers.
Most of the first-generation computers worked on the principle of storing program instructions along with data in memory of computer(stored program concept) so that they could automatically execute a program without human intervention. Memory of these computers used electromagnetic relays, and users fed all data and instructions into the system using punched cards. Programmers wrote instructions in machine and assembly languages are difficult to work with, only a few specialists understood how to program these early computers.
Characteristic features of first-generation computers are as follow: -
They were the fastest calculating devices of their time.
They were too bulky in size, requiring large rooms for installation.
They used thousands of vacuum tubes that emitted large amount of heat and burnt out frequently. Hence, the rooms/areas in which these computers were located had to be properly air-conditioned.
Each vacuum tube consumed about half a watt of power. Since a computer typically used more than ten thousand vacuum tubes, power consumption of these computers was very high.
As vacuum tubes used filaments, they had a limited life. Because a computer used thousand of vacuum tubes, these computers were prone to frequent hardware failure.
Dur to low mean time between failures, these computers required aonstant maintenance.
In these computers, thousands of individual components were assembled manually by hand into electronic circuits. Hence, commercial production of these computers was difficult and costly.
Since these computers were difficult to program and use, they had limited commercial use.