Since its programs were hardwired —

Since its programs were hardwired — that is, the programs operating the comput¬er were established by physically changing the patterns of the wires interconnecting the vacuum tubes — the machine was not so flexible in operation. These limitations made it difficult to detect errors and to change the programs. And yet, the project was successful and the ENIAC was used for many years to solve ballistic problems.
2. The EDVAC (1946-1952)
Although the idea of an automatic computing engine oc¬curred first to Charles Babbage in 1832, it was more than a cen¬tury later, in 1945, that John von Neumann set out the princi¬ples that fixed the pattern of computer design.
Dr.John von Neumann, professor of mathematics at the Prinston Institute of Advanced Study, together with P.Eckert, J.Mauchly and Goldstine became a project member of a new improved computer, the Electronic Discrete Variable Comput¬er (EDVAC). Von Neumann was a major contributor to the project as he developed the concept of storing instructions as well as data in the memory of the computer. As a result it be¬came possible to replace the writing board, which so seriously handicapped the operation of the ENIAC.
Von Neumann is also given a share of the credit for intro¬ducing the idea of storing both instructions and data in a bina¬ry code instead of decimal numbers or human-readable words.