The first operating system was used with the ENIAC (Electronic Numerical Integrator and Computer). It was very hard to make ENIAC do work. How the operating system worked was based on how the switches and cables were put together and depending on this factor punch cards would make a
result. While this was an operating system of a kind, it is not what is thought of as one in modern times.
Video: Using an old UNIX system.
The first operating system that looked and felt like operating systems in the modern age was UNIX, made in 1969 by Bell Labs. It had a small kernel and many tiny programs that could be put together to work with user input and data. Many of its
features were taken from
Multics, an older operating system made in 1964.