ENIAC was the first programmable, electronic, general-purpose digital computer, completed in 1945. Other computers had some of these features, but ENIAC was the first to have them all. It was Turing-complete and able to solve "a large class of numerical problems" through reprogramming.
Four ENIAC panels and one of its three function tables at the School of Engineering and Applied Science at the University of Pennsylvania
Glenn A. Beck (background) and Betty Snyder (foreground) program ENIAC in BRL building 328. (U.S. Army photo, c. 1947–1955)
Cpl. Irwin Goldstein (foreground) sets the switches on one of ENIAC's function tables at the Moore School of Electrical Engineering. (U.S. Army photo)
Programmers Betty Jean Jennings (left) and Fran Bilas (right) operating ENIAC's main control panel at the Moore School of Electrical Engineering, c. 1945 (U.S. Army photo from the archives of the ARL Technical Library)
A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations (computation). Modern digital electronic computers can perform generic sets of operations known as programs. These programs enable computers to perform a wide range of tasks. The term computer system may refer to a nominally complete computer that includes the hardware, operating system, software, and peripheral equipment needed and used for full operation; or to a group of computers that are linked and function together, such as a computer network or computer cluster.
A human computer, with microscope and calculator, 1952
The Ishango bone, a bone tool dating back to prehistoric Africa
The Antikythera mechanism, dating back to ancient Greece circa 150–100 BCE, is an early analog computing device.
Charles Babbage c. 1850