Introduction to

ENIAC( Electronic Numerical Integrator And Computer)
Developed by 
Eckert 
and 
Mauchly 
at the university of Pennsylvania. This was the first 
electronic calculator and first general purpose digital computer. This machine was enormous, 
weighing 30 tons., occupying 15,000 square feet of floor space and containing over 18,000 
vacuum tubes. While running it used to consume over 140 KWh of power. It had the capacity 
to perform 5,000 additions per second. Its memory consisted of 20 “accumulators” each 
capable of holding a 10 digit decimal number. The following are some of the characteristics of 
ENIAC.
• ENIAC did not use internally stored programs. Programs were wired on boards 
similar to a telephone switch board. 
• One of the major drawbacks of ENIAC was that it had to be programmed 
manually by setting switches and plugging and unplugging cable
Activity Conclusion.
Devices that predates modern day computers are Abacus, Pascal’s calculator, the Difference 
engine, Herman Hollerith’s Tabulating Machine, Mark I and ENIAC. Among them ENIAC was 
regarded as the first electronic calculator and digital computer.
Assessment: Reflective Activities
• What was the function of the component named mil in the difference engine?
• What were the distinguishing features of ENIAC from modern day computers?
• What makes different a computer from any other electronic device?

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Unit 1: Introduction to Computer Systems
29
Answers
• It performs basic arithmetic operations
• ENIAC did not use internally stored programs. Programs were wired on boards 
similar to a telephone switch board. And it had to be programmed manually 
by setting switches and plugging and unplugging cables. Humanbeings or the 
machine operator play the role of modern day operating systems
• It can store information permanently, it has big computing power, highly 
accurate,etc