Workshop: C Programming under the UNIX Operating System

1. Workshop:C Programming under theUNIX Operating System Ran Eshel

2. Lecture Overview • Course overview and administration – requirements, syllabus, books and tools • About UNIX, Linux and Open Source • About C

3. Course Overview • In this course we forget about: • OOP • GUI (Graphical User Interface) • Instead, we go back to: • Procedural programming • CUI (Character User Interface), also known as command-line interface

4. Course Requirements • Exercises • Approximately 8 programming exercises • Submission of all exercises is compulsory,missing exercises count as 0 in the average • First exercises submitted in pairs, others TBD • Grades of different exercises may be weighted based on their size and difficulty

5. Course Requirements • Exam • With open material • Mostly programming (C and C Shell),some background knowledge • Grading policy • Final Grade = 80% exam + 20% exercises • Important: in order to pass the course you must pass each component separately

6. Syllabus • Introduction to the UNIX environment • UNIX tools • Text processing • Pipes • Text editing with vi • UNIX Shell programming

7. Syllabus • The C programming language • Types, operators and expressions • Control flow • Functions • Pointers and Arrays • Structures

8. Course Books • A Book on C: Programming in C (4th Edition)–Al Kelley, Ira Pohl • In Amazon • In IDC Library • The C Programming Language (2nd Edition) – Brian Kernighan, Dennis Ritchie • In Amazon • In IDC Library

9. Course Books • A Practical Guide to the UNIX System(3rd Edition) – Mark G. Sobbel • In Amazon • In IDC Library • A Practical Guide to the Linux Commands, Editors, and Shell Programming • In Amazon • In IDC Library

10. Course Tools • All of the exercises in the course should be written on the IDC Linux server • The server can be accessed from anywhere using a remote client such as PuTTY • Files can be copied to and from the server using a secure FTP client (such as WinSCP) • Resources: SSH clients for MS-Windows

11. Local Linux Installation • It is also possible (but not required)to install Linux on your home PC • There are many Linux variants. Recommended: Fedora, Ubuntu • Each can be used in two ways • Full install – not simple, and somewhat risky • Live media – good as a demo, but has many disadvantages for real work

12. Lecture Overview • Course overview and administration – requirements, syllabus, books and tools • About UNIX, Linux and Open Source • About C

13. Why Study UNIX? • For the past two decades, the computing world has been divided between: • The UNIX family (including Linux) • Microsoft Windows • Although recent years have seen a decline in UNIX installations, the growth of Linux compensates for this, and more

14. Why Study UNIX? • During most of your studies you concentrate on Windows • This course will complete your operating system education with UNIX • An additional benefit: every programmer must have at least some experience with command-line and with shell scripting

15. UNIX Advantages • Stability • Processes are isolated • Crashes are rare, and locally contained • Flexibility • Modular structure, small and simple elements • Source code is usually available (Linux) • Real multi-user support

16. UNIX • Portability • Some UNIX variant is available for almost every existing platform • The first major operating system to be written in a high level language • Text – A Simple Interface • Use of text streams as program interfaces • Use of text files to store data

17. A Brief History of UNIX • Mid 60's – Multics, a large multi-user operating system project (AT&T, GE, MIT) • 1969 – Multics project is behind schedule, Ken Thompson starts working on UNIX • A smaller version (Multics does many things;UNIX does one thing well – run programs) • First UNIX version is operational before Multics • 1970 – UNIX officially named and running

18. UNIX • "The number of UNIX installations has grown to 10, with more expected." The UNIX Programmer’s Manual, 1972 • "The number of UNIX variants has grown to dozens, with more expected." Rob Pike, Bell Labs, 2001

19. The UNIX Family • During most of UNIX's long history, two major versions existed in parallel: • System V, a commercial version maintainedby AT&T Bell Labs (original creators of UNIX) • BSD (Berkley Software Distribution), created first with the cooperation of AT&T, but lateras a competing free alternative • Linux combines most features of both

20. Branches of the UNIX Family

21. 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

22. Linux • An Open Source version of UNIX • A complete operating system, including GUI, distributed freely over the internet • Not only executables are available, but also the complete source code • Distributed under the GNU General Public License

23. Free Software (Open Source) • The GPL grants users with the freedom to: • Run the program for any purpose • Study how the program works, and modify it • Redistribute copies • Improve the program, and release the improvements to the public • The only requirement – derivative works must also be licensed under the GNU GPL

24. Free Software (Open Source) • Free Software (also called Open Source),is not freeware – it can cost money • "Free software is free as in 'free speech',not as in 'free beer'" Richard Stallman, The Free Software Foundation • Surprisingly, open source projects are as fast and as reliable as commercial projects

25. Lecture Overview • Course overview and administration – requirements, syllabus, books and tools • About UNIX, Linux and Open Source • About C

26. Why Study C? • A small and simple language • Helps clarify basic computer concepts • Still the most efficient language • Does not have the overhead of Object Oriented languages • Still the most powerful language • If you can't do it in C, you just can't do it

27. C and OOP • C is the basis for the most common Object Oriented languages – C++, Java and C# • C is perfect for procedural programming • Procedural programming is not the opposite of Object Oriented Programming – it is an essential part of it • OOP can be seen as an extension of procedural programming

28. C and UNIX • C is the native language of UNIX, and the language in which UNIX itself is written • Together, C and UNIX revolutionized the computer world • The combination of a UNIX environment coupled with C programming is still common in many large companies

29. A Brief History of C • The first version of UNIX was written in PDP-7 assembly language (like most operating systems of the time) • Ken Thompson wanted to rewrite it in some high-level language for two reasons: • Clarity – ease of modification • Portability to other machines

30. A Brief History of C • The PDP-7 was notpowerful enough to hosta compiler for any existinghigh-level language • To overcome this problem,a new language was written Ken Thomson and Dennis Ritchie on the PDP-11

31. A Brief History of C • The new language was a simplified version of BCPL, and was therefore called B • Later, B was enhanced by Dennis Ritchie,and the new language was called C • The most significant improvement – types • In 1973, UNIX was rewritten in C • Shortly afterwards it was ported to thePDP-11, and then to many other machines

32. A Brief History of C • The performance of UNIX written in C was very similar to that of operating systems written in Assembly language • Since then, performance has become C's most prominent feature, making it the standard operating systems language