CSCI 243: C & UNIX Kirk Anne South 124A

Course Description 5 weeks Teach you how to use UNIX Teach you how to program in C Practical, not theoretical “Tricks of the trade” How to not spend hours in front of the computer

Grading The only way to learn C is to program. Programs will be graded on: –Correctness –Style –Spelling Programs must produce correct answers. If errors, programs should exit gracefully.

Projects Syllabus tells you what you need for a “C”. –Three programs by end of week 2. –Three programs by end of week 3. –Three programs by end of week 4. –One program and final project, end of week 5. Final project –Can be from another class to save time

Points A250+ A-225 B+200 B175 B-150 C+125 C100 C-75 D50 E25

Final Project You can use a project from another class Or… –Write a library of functions for a stack and a “reverse Polish notation” calculator (HP) –Write a “substantial program”

Tentative Schedule Week 1: Intro Week 2: Basic C Week 3: Structures Week 4: Pointers Week 5: Shell Scripts Editors, X windows Control statements Functions Debugging, profiling Course Wrapup

Plagiarism The exercises are published on the Internet. I know this. This class may be your only chance to practice C with the “safety net”. This is where you will learn how C works. Cheating will only hurt you.

The History (!!) of UNIX

History of UNIX 1969… –The Year of Woodstock –Armstrong walks on the moon –The Year of “Space Travel” –A PDP-7 sits in a corner of a lab… 9K of RAM Paper tape drive Teletype 33 terminal

A plan comes together... Dennis Ritchie and Ken Thompson take a PDP-7 and use their research at AT&T to produce the first computer that can play “Space Travel”. Based on research from GE, MIT and AT&T called Multics, a powerful operating system, UNIX is born. But much simpler...

Multics Multiplexed Information & Computing Service Too big to work but had… –Interactivity –Shared Physical and Virtual Memory –Symmetric Multiprocessing –Security –Software Engineering –Hierarchical File Storage System –Programmed in PL/I

UNIX Took a lot of Multics ideas But reduced the complexity Originally written in assembly Uses a “layered” approach to achieve complexity

What’s “C” got to do with it? C is derived from BCPL, another language available on Multics. C is a “middle level” language. –Low level - Assembly (fast but only one CPU) –High level - FORTRAN, PL/I (slow, but easy) C allows you the power of assembly with the ease of a high level language.

C makes UNIX portable Kernighan & Ritchie write a C compiler to prepare code for the PDP-7 UNIX project. Made C small and easy to port. When they got a PDP-11 with 24K, it ported quickly. After converting the UNIX system from assembly to C, it ported quickly too.

UNIX becomes popular Once a C compiler is written for a new CPU, the UNIX operating system can be ported soon after. AT&T couldn’t sell UNIX because the gov’t said that their phone monopoly was enough. They gave it away to universities...

UNIX meets Berkeley... CS graduate students got their hands on the source code for an entire operating system. The prices for PDP-8s and PDP-11s enabled research universities to allow grad students to work on their “own”computers. UC Berkeley graduates take the source and run...

BSD UNIX Bill Joy (one of the founders of Sun Microsystems), leads the CSRG to build a new version of UNIX called Berkeley Software Disitribution (BSD). SUN actually stands for Stanford University Network.

CSRG products “vi” (vee-eye) sendmail lint make TCP/IP (Internet) telnet, ftp, rlogin, rsh, rcp, etc…

The “Tower of Babel” AT&T invents UNIX Berkeley reinvents UNIX as BSD UNIX Corporations realize it’s cheaper to use UNIX Everybody has a version of UNIX Two major types –AT&T System V and BSD

Corporate UNIX In the early 1990’s, corporations wanted to have a “corporate UNIX” that conformed to standards. The Open Software Foundation was formed to create a “standard UNIX”. AT&T wanted to keep the UNIX name.

What goes around, comes around AT&T joined forces w/ Sun (Bill Joy,BSD) to create the UNIX Software Labs and System V Release 4 (SVR4). Sun drops development on its BSD system Solaris is born...

UNIX Terms

“Buzz Word” Compliant Multiuser –more than one person can use the system Multitasking –more than one job can be done at a time Hierarchical –Different levels, resembling an upside-down tree

File System

Shell Kernel The “UNIX” Way... CPU

Logging in...

Logging into a UNIX system Telnet to a system X Windows (on the console) “rlogin”

Changing your password “passwd”

Getting out “logout” “exit” Exit the Window System

Basic UNIX commands Remember that PDP-7 with 9K of memory and 110 baud Teletype 33 terminal???

Basic UNIX commands date ls cat file mv old new cp original new rm file more file pwd See what time it is List directory Display a file Move a file (rename) Copy a file Remove a file Page through a file Print working directory

UNIX Files One of the strengths of UNIX is that a “file” is just considered a stream of information with a starting point and an optional length. UNIX can treat almost anything as a file. Because of this, handling data is very easy.

Directories A directory is a special type of file that holds information about other files. Can be used to store similar files –mkdirMake a directory –cdChange directory –rmdirRemove an empty directory –lsList a directory

Wildcards and “Regular Expressions” A star “*” indicates all files that match. A question mark “?” means just one character. Brackets can restrict which letters are used. –[A-Z]All upper case letters –*[02468]All files that end w/even numbers –[aeiou]*All files that start w/vowels

Next time... Man pages Editors X windows File permissions How to handle processes

For more information... (Check out the UNIX CBTs)