From Multics to Linux: The Untold History of Modern Operating Systems

Multics – Early Multiprocessing OS

Multics (MULTiplexed Information and Computing System) was a pioneering time‑sharing, multitasking operating system started in 1964 by Bell Labs, MIT and General Electric. Its design goal was to connect up to 1,000 terminals and support about 300 simultaneous users, demonstrating true concurrent execution on a mainframe.

From Multics to Unix

In 1970 Ken Thompson, working at Bell Labs, found the existing Multics prototype unsuitable for interactive use. Using an idle PDP‑7 he built a simplified, single‑machine system that implemented a file system, process abstraction, device files and a command‑line interpreter. The prototype was nicknamed UNICS (later Unix). Thompson also created the B programming language for system‑level code; Dennis Ritchie later replaced B with the C language, which became the primary language for Unix development.

BSD – Berkeley’s Unix Derivative

Bell Labs released Unix Version 5 in July 1974, making the source available to universities. The University of California, Berkeley extended Version 6 and released the Berkeley Software Distribution (BSD) in 1978. Legal disputes with AT&T over licensing (AT&T charged roughly $40 000 per copy) and the eventual breakup of AT&T limited BSD’s commercial adoption.

GNU Project and Copyleft

In 1983 Richard Stallman launched the GNU Project to build a completely free Unix‑like operating system. The project produced essential tools—editors, compilers (gcc), shells (bash), and the GNU C library—but the kernel (initially the Hurd on GNU Mach) remained unfinished, delaying a full GNU system.

Linux Kernel Development

In August 1991 Linus Torvalds, a 21‑year‑old student at the University of Helsinki, announced on the comp.os.minix newsgroup that he was writing a “free operating system” for the 386 AT platform. He had already ported bash 1.08 and gcc 1.40 to his code base.

“I am working on a (free) operating system… I have ported bash (1.08) and gcc (1.40)… It runs on a 386 AT, is not portable, and may never support anything beyond AT disks.”

The first public release, kernel version 0.01, appeared on a Finnish university FTP server in August 1991 with 10,239 lines of C code. Version 0.02 followed a month later, adding a multithreaded file system. Both releases were distributed under the GNU General Public License (GPL), providing a free‑software license for the kernel.

Linux 1.0.0 was released on 14 March 1994, containing 176,250 lines of code. With the GNU tools completing the user‑space components, the combined system became known as GNU/Linux, although it is commonly referred to simply as “Linux”.

Key Technical Milestones

1964 – Multics project begins (time‑sharing, 1000 terminals, 300 users).

1970 – Thompson creates UNICS on a PDP‑7; B language introduced.

1974 – Unix Version 5 released; source distributed to academia.

1978 – BSD released, extending Unix V6.

1983 – GNU Project started; GNU tools (gcc, bash, coreutils) become available.

1991 – Linux kernel 0.01 (10,239 LOC) and 0.02 released under GPL.

1994 – Linux 1.0.0 (176,250 LOC) released, marking the first stable GNU/Linux system.