The First Personal Computer to Use an Operating System Not Based on Unix

When discussing the first personal computer to use an operating system (OS) not based on Unix, it's crucial to understand the evolving definitions of personal computers and what constitutes an operating system. This article explores the early history of personal computing and the significance of CP/M, the first microcomputer OS not based on Unix.

The First Personal Computer: MITS Altair 8800

Many historians and enthusiasts consider the MITS Altair 8800 to be the first personal computer, released in 1975. Its first operating environment was a BASIC interpreter developed by Microsoft, which was their first product. However, if we do not classify a BASIC interpreter as an operating system, the significance shifts to the CP/M operating system released in 1974.

The Evolution of CP/M

CP/M (Control Program for Microcomputers) was developed in 1974 initially to run on the Intel Intellec 8 development system for the Intel 8080 microprocessor. While this system was indeed a microcomputer and shared many characteristics with the MITS Altair 8800, the Intellec 8 computers were not marketed or sold widely.

The Pre-UNIX Era of Personal Computers

The period between 1975 and 1980 saw the emergence of numerous non-UNIX-based operating systems on various personal computers. For instance, although UNIX was initially developed in 1969 for minicomputers, its variants started appearing on microcomputers around 1980. One of the early examples was the Onyx 8002, which ran a variant of UNIX based on the Zilog Z8000 microprocessor.

Alternative Choices Before the IBM PC

In this era, Apple is often cited as creating the first actual personal computer you could buy and use in your home. However, for the purpose of this article, we will focus on the Apple II, which was introduced in 1977. The Apple II used a custom designed BASIC interpreter and later adopted the Cotorrent operating system, which was not based on UNIX.

The IBM PC and Its Successors

The IBM PC, introduced in 1981, and its successors, such as the PCjr, PC/XT, and AT, marked a significant transition. The PC/XT and its successors could run multiple operating systems, including Minix, DOS, and even Xenix. The IBM PC became the standard for personal computing, with its MS-DOS (later MS-Windows) becoming the de facto standard.

Conclusion

Through the evolution of personal computing, it is clear that the CP/M operating system, developed in 1974 for the Intel Intellec 8, was the first microcomputer OS not based on UNIX. This contrasts with the later entries such as the Apple II and the IBM PC, which either adopted their own proprietary operating systems or modifications of UNIX variants.

Understanding the historical context of OS development is key to appreciating the advancements and innovations in personal computing. CP/M set the stage for future operating systems, even if it was not as widely commercialized as others like DOS or UNIX.