One of the very first drafts which would develop into the personal computers we know today came from the mid 1900s, and they weren't anything like the PCs we have today.
The first PCs were huge in size, and required many engineers to keep it running, and the main reason they had them weren't for mass production nor were they even meant for personal use, but they were used for military firing in WWII. During WWII, the US military was in quick demand for quick computation. They wanted to be able to make a bunch of artillery firing tables so that gunners could determine conditions, a target, and weapon settings. This would take weeks for humans to calculate on their own, making a need for a device that could to it automatically.
The Electronic Numerical Integrator and Computer or ENIAC for short was the most popular of the first computers. In Moore School of Electronic Engineering of the University of Pennsylvania, Philadelphia, the Electronic Numerical Integrator and Computer was first developed, with the match sparking up this mastery of engineering being a sponsorship by the U.S. War department. Along with the innovation being huge (approximately 50-30ft), it also required its own air conditioning system, generating somewhere around 174 kilowatts of heat. Despite its complexities, it was by far the best programming machine of its time, thus meaning its untapped potential with future developments was huge.
While the Electronic Numerical Integrator and Computer was not a direct path into what the modern PC would be, it did come with a statement that proved to universities and large companies that computers were something big to invest their money in. As technology grew throughout the world, we had more and better ways to make computer technology smaller and quicker.
For example Bell Labs in 1948 introduced the transistor to the world which could carry electronic currents while amplifying them, as well as being very small. In around 1958, Texas Instruments put a alot of electronic parts into a small silicon chip.
The biggest pathway into the PCs future came in the form of microprocessors. These small devices of an extremely small size could compute programs, manage data, and more all in a very compact size.
Once the first official PCs were created, it didn't take long before they launched into an explosive force. Developments such as the Graphical User Interface was adopted to make the PC experience more usable instead of writing long and complex commands, and many companies started producing and making computers commonplace in schools, offices, homes, and just about everywhere. These computers much like modern day became popular from uses of creating spreadsheets, word processing, hobbies, and games.
Today we see PCs being used for similar reason, except the exploding technological advancements have livened growth in so many directions. Many PC functions are now being used for phones, and with better technology comes better graphics, faster speeds, and the cultural importance on the internet and social media making the technology as relevant as ever.