ABC
The Atanasoff-Berry Computer (ABC) was the worlds first digital electronic computer the ABC while fully electronic was not programmable meaning that it was made for a single purpose only.
Harvard Mark I
Next in the world of computers was the Harvard Mark I funded by IBM and built by Howard Aiken with assistance from IBM empployees. The Mark I became operational at Harvard University in May of 1944
Enter the ENIAC
Then the ENIAC which stands for Electronic Numerical Integrator and Computer. The ENIAC was the first programmable all purpose electronic computer in the world. It could add or subtract 5000 times per second unlike the Colossus which couldn't add. The ENIAC could also multiply, devide and square root. Its memory was limited to 20 words or about 80 bytes. The construction of the ENIAC lasted from 1943-1945 when it was fully functional, for the next ten years it was used constantly.