The new operating system was initially without organizational backing, and also without a name. At this stage, the new operating system was a singletasking operating system, not a multitasking one such as Multics. The name Unics (Uniplexed Information and Computing Service, pronounced as "eunuchs"), a pun on Multics (Multiplexed Information and Computer Services), was initially suggested for the project in 1970. Brian Kernighan claims the coining for himself, and adds that "no one can remember" who came up with the final spelling Unix. Dennis Ritchie and Doug McIlroy also credit Kernighan.

When the Computing Sciences Research Center wanted to use Unix on a machine larger than the PDP-7, while another department needed a word processor, Thompson and Ritchie added text processing capabilities to Unix and received funding for a PDP-11. For the first time in 1970, the Unix operating system was officially named and ran on the PDP-11. A text-formatting program called roff and a text editor were added. All three were written in PDP-11 assembly language. Bell Labs used this initial text-processing system, consisting of Unix, roff, and the editor, for text processing of patent applications. Roff soon evolved into troff, the first electronic publishing program with full typesetting capability.

As the system grew in complexity and the research team wanted more users, the need for a manual grew apparent. The UNIX Programmer's Manual was published on 3 November 1971; commands were documented in the "man page" format that is still used, offering terse reference information about usage as well as bugs in the software, and listing the authors of programs to channel questions to them.

After other Bell Labs departments purchased DEC PDP-11s, they also chose to run Unix instead of DEC's own operating system. By Version 4 it was widely used within the laboratory and a Unix Support Group was formed, helping the operating system survive by formalizing its distribution.

In 1973, Version 4 Unix was rewritten in the higher-level language C, contrary to the general notion at the time that an operating system's complexity and sophistication required it to be written in assembly language. The C language appeared as part of Version 2. Thompson and Ritchie were so influential on early Unix that McIlroy estimated that they wrote and debugged about 100,000 lines of code that year, stating that "may safely be assumed to be attached to almost everything not otherwise attributed". Although assembly did not disappear from the man pages until Version 8, the migration to C suggested portability of the software, requiring only a relatively small amount of machine-dependent code to be replaced when porting Unix to other computing platforms. Version 4 Unix, however, still had considerable PDP-11-dependent code and was not suitable for porting. The first port to other platform was made five years later (1978) for Interdata 8/32.

The Unix operating system was first presented formally to the outside world at the 1973 Symposium on Operating Systems Principles, where Ritchie and Thompson delivered a paper. This led to requests for the system, but under a 1956 consent decree in settlement of an antitrust case, the Bell System (the parent organization of Bell Labs) was forbidden from entering any business other than "common carrier communications services", and was required to license any patents it had upon request. Unix could not, therefore, be turned into a product. Bell Labs instead shipped the system for the cost of media and shipping. Ken Thompson quietly began answering requests by shipping out tapes and disks, each accompanied by – according to legend – a note signed, "Love, Ken".
List all the people mentioned in this paragraph on the history of Unix
- Brian Kernighan
- Dennis Ritchie
- Doug McIlroy
- Ken Thompson