UNIX: History, Characteristics, and Philosophy
In simple terms, UNIX is an Operating System that was developed in the mid-1960s. Operating System (OS) is software that is used to interact with the machine hardware.
Originally, UNIX for made for programmers to develop software rather than non-programmers. This Operating System is written in the C programming language. It was developed by Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna at Bell Labs.
**It is freeware**Freeware is a terminology used for something available for free.UNIX is a freely available Operating System.
**It is Open Source**Open Source Software or Operating Systems are those whose source code(original code) is freely available and can be redistributed and modified. Note: Points 1 and 2 can be termed as FOSS (Freeware and Open source software)
**It supports CUI vs GUI Interface**CUI stands for Character User Interface. It works by allowing the user client to issue commands as one or more lines of text (referred to as command lines) to a program. For example, Windows Command Prompt. GUI stands for Graphical User Interface. It is a computer program that enables a person to communicate with a computer through the use of symbols, visual metaphors, and pointing devices.
**It is a multi-user operating system**Unix can be used by multiple users concurrently and simultaneously.
**It is a multi-tasking operating system**Various tasks can be performed simultaneously and collectively.
**It is more secure**Unix systems are by no means infallible, but one of their key advantages lies in the way account privileges are assigned. In Windows, users are generally given administrator access by default, which means they pretty much have access to everything on the system, even its most crucial parts. So, then, do viruses. It’s like giving terrorists high-level government positions. Moreover, Unix is used by tech-savvy users which makes it less vulnerable to cyber-attacks and viruses
The** Unix philosophy**, originated by Ken Thompson, is a set of cultural norms and philosophical approaches to minimalist, modular software development. It is based on the experience of leading developers of the Unix operating system.
The ‘Unix philosophy’ originated with Ken Thompson’s early meditations on how to design a small but capable operating system with a clean service interface. It grew as the Unix culture learned things about how to get maximum leverage out of Thompson’s design. It absorbed lessons from many sources along the way.
The Unix philosophy is not a formal design method. It wasn’t handed down from the high fastnesses of theoretical computer science as a way to produce theoretically perfect software. Nor is it that perennial executive’s mirage, some way to magically extract innovative but reliable software on too short a deadline from unmotivated, badly managed, and underpaid programmers.
The Unix philosophy (like successful folk traditions in other engineering disciplines) is bottom-up, not top-down. It is pragmatic and grounded inexperience. It is not to be found in official methods and standards, but rather in the implicit half-reflexive knowledge, the expertise that the Unix culture transmits. It encourages a sense of proportion and skepticism — and shows both by having a sense of (often subversive) humor.
Doug McIlroy, the inventor of Unix pipes and one of the founders of the Unix tradition, had this to say at the time :
(i) Make each program do one thing well. To do a new job, build afresh rather than complicate old programs by adding new features.
(ii) Expect the output of every program to become the input to another, as yet unknown, program. Don’t clutter output with extraneous information. Avoid stringently columnar or binary input formats. Don’t insist on interactive input.
(iii) Design and build software, even operating systems, to be tried early, ideally within weeks. Don’t hesitate to throw away the clumsy parts and rebuild them.
(iv) Use tools in preference to unskilled help to lighten a programming task, even if you have to detour to build the tools and expect to throw some of them out after you’ve finished using them.
He later summarized it this way (quoted in A Quarter Century of Unix [Salus]):
This is the Unix philosophy: Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface.
Rob Pike, who became one of the great masters of C, offers a slightly different angle in Notes on C Programming [Pike]:
Rule 1. You can’t tell where a program is going to spend its time. Bottlenecks occur in surprising places, so don’t try to second guess and put in a speed hack until you’ve proven that’s where the bottleneck is.
Rule 2. Measure. Don’t tune for speed until you’ve measured, and even then don’t unless one part of the code overwhelms the rest.
**Rule 3. **Fancy algorithms are slow when n is small, and n is usually small. Fancy algorithms have big constants. Until you know that n is frequently going to be big, don’t get fancy. (Even if n does get big, use Rule 2 first.)
**Rule 4. **Fancy algorithms are buggier than simple ones, and they’re much harder to implement. Use simple algorithms as well as simple data structures.
Rule 5. Data dominates. If you’ve chosen the right data structures and organized things well, the algorithms will almost always be self-evident. Data structures, not algorithms, are central to programming.[9]
Rule 6. There is no Rule 6.
Ken Thompson, the man who designed and implemented the first Unix, reinforced Pike’s rule 4 with a gnomic maxim worthy of a Zen patriarch:
When in doubt, use brute force.
More of the Unix philosophy was implied not by what these elders said but by what they did and the example Unix itself set. Looking at the whole, we can abstract the following ideas:
Rule of Modularity: Write simple parts connected by clean interfaces.
Rule of Clarity: Clarity is better than cleverness.
Rule of Composition: Design programs to be connected to other programs.
Rule of Separation: Separate policy from mechanism; separate interfaces from engines.
**Rule of Simplicity: **Design for simplicity; add complexity only where you must.
Rule of Parsimony: Write a big program only when it is clear by demonstration that nothing else will do
Rule of Transparency: Design for visibility to make inspection and debugging easier.
Rule of Robustness: Robustness is the child of transparency and simplicity.
**Rule of Representation: **Fold knowledge into data so program logic can be stupid and robust.
Rule of Least Surprise: In interface design, always do the least surprising thing.
Rule of Silence: When a program has nothing surprising to say, it should say nothing.
Rule of Repair: When you must fail, fail noisily and as soon as possible.
Rule of Economy: Programmer time is expensive; conserve it in preference to machine time.
**Rule of Generation: **Avoid hand-hacking; write programs to write programs when you can.
Rule of Optimization: Prototype before polishing. Get it working before you optimize it.
Rule of Diversity: Distrust all claims for “one true way”.
Rule of Extensibility: Design for the future, because it will be here sooner than you think.