What are the features of first generation computers?

Following are some of the important features of First generation computers:

Used vacuum tubes to control and amplify electronic signals.
Huge computers that occupied lot of space.
High electricity consumption and high heat generation.
Were unreliable since they were prone to frequent hardware failures.
Commercial production was difficult.
They were very costly and required constant maintenance.
Continuous air conditioning was required.
Programming was done in machine language although assembly language also started at the end of this generation
Example: ENIAC , EDVAC , UNIVAC 1