Understanding Linux’s Origins

Understanding Linux’s Origins

In 1991, as is also true today, computers were classified by their sizes and capabilities. Computers could belong to any of a handful of categories, ranging from desktop personal computers (PCs) to supercomputers.  x-86-based computers, which are the direct ancestors of today’s PCs, dominated the PC marketplace of 1991; however, other types of PCs were available, including Macs. Such computers generally used different C.P.Us and ran their own custom OSs.

In 1991, most PCs ran Microsoft’s Disk Operating System (MS-DOS, PC-DOS, or DOS).

DOS was extremely limited by today’s standards; this single-tasking OS  (capable of running only one application at a time) didn’t even take full advantage of the memory or C.P.Us available at the time.

The versions of Microsoft Windows available in 1991 ran on top of DOS. Although the initial versions of Windows helped to work around some of DOS’s limitations, they didn’t fundamentally fix any of them. 

These early versions of Windows employed cooperative multitasking, for instance, in which programs could voluntarily give up CPU up time to other processes. The DOS kernel could not wrest control from a program that hogged CPU time. 

Above the PC level, Unix was a common OS in 1991.

Compared to DOS and the version of Windows of that time, Unix was a sophisticated OS. 

Unix supported multiple accounts and provided true preemptive multitasking, in which the kernel could schedule CPU time for programs, even if the programs didn’t voluntarily give up control. These features were practical necessities for many servers and for multi-user computers such as minicomputers and mainframes.

As time progressed, the capabilities of each class of computer have grown. 

By most measures, today’s PCs have the power of the minicomputers or even the mainframes of 1991.

The OSs used on the PCs of 1991 didn’t scale well to more powerful hardware. Just having more computing power itself, however, didn’t remove the limitations of DOS. 

For this reason, DOS and its small-computer contemporaries have been largely abandoned in favour of Unix and other alternatives.

In 1991, Linus Torvalds was a student at the University of Helsinki, studying computer science. He was interested in learning about both Unix and the capabilities of the new  x-86 computer he’d just purchased. Torvalds began the program that would become the Linux kernel as a low-level terminal emulator—a program to connect to his university’s larger computers. As his program grew, he began adding features that turned his terminal program into  something that could be better described as an OS kernel. 

Eventually, he began what computers today can be classified in much the same way as in1991, although some details have changed.

A notable addition are embedded computers, as in smartphones.

Unix was not the only multi-user, multitasking OS in 1991. 

Others, such as Virtual Memory System (VMS), were available. 

Unix is most relevant to Linux’s history, though.  

Today’s versions of Windows are not derived from DOS. 

Instead, they use anew kernel that shares many design features with VMS.

Unix’s history, in turn, stretched back two more decades, to its origin at AT&T in 1969. Because AT&T was a telephone monopoly in the United States at that time, it was legally forbidden from selling software.

Therefore, when its employees created Unix, AT&T basically gave the OS away. 

Universities were particularly enthusiastic about adopting Unix, and some began modifying it, because AT&T  made the source code available. 

Thus Unix had a two-decade history of open software development to start. 

Most Unix programs were distributed as source code, because Unix ran on a wide variety of hardware platforms—binary programs made for one machine would seldom run on a different machine.

Early on, Linux began to tap into this reservoir of available software.

Linux developers were particularly keen on the GNU project’s software, so Linux quickly accumulated a collection of GNU utilities. 

Much of this software had been written with workstations and more-powerful computers in mind, but because computer hardware kept improving, it ran fine on the  x-86 PCs of the early 1990s.

Linux quickly acquired a devoted following of developers who saw its potential to bring workstation-class software to the PC. These people worked to improve the Linux kernel, to make the necessary changes in existing Unix programs so that they would work on Linux, and to write Linux Specific support programs.

By the mid-1990s, several Linux distributions existed, including some that survive today.

Slackware was released in 1993 and Red Hat in 1995, for example.