CSCI 243: C & UNIX

Kirk Anne

South 124A

kma@geneseo.edu

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

• A 250+• A- 225• B+ 200• B 175• B- 150

• C+ 125• C 100• C- 75• D 50• E 25

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

/b inU tilit ies

/e tcS ys tem files

/liblib ra ries

/u s r/b in /u s r/lib /u s r/s rc

/u s r/loca l/b in /u s r/loca l/ lib /u s r/loca l/s rc

/u s r/loca lL oca l p rog ram s

/u s rU ser P rog ram s

/h om eU ser F iles

/(roo t d irec to ry)

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– mkdir Make a directory– cd Change directory– rmdir Remove an empty directory– ls List 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...

http://cbt.geneseo.edu/

(Check out the UNIX CBTs)