Class Info

Class: TTh 1:15–2:30, Science Center 199
Professor: Vasanta Chaganti
Piazza: Q&A Forum
GitHub: Swarthmore GitHub Enterprise

Office hours (Vasanta): SCI 252D, Mon: 3:00 - 4:30 PM, Thu: 2:30 - 4:00 PM
Office hours (Scout): SCI 262A, Thu: 11:15 - 12:15 PM, Fri: 3:00 - 4:00 PM
Office hours (Rich): SCI 251, Mon: 9:15 - 10:15 AM, Mon: 1:30 - 2:30 PM

Weekly Lab Sessions
Section A	Rich Wicentowski	Wednesdays 8:50—10:20 AM	Science Center 240
Section B	Scout Sinclair	Wednesdays 1:15—2:45 PM	Science Center 240
Section C	Vasanta Chaganti	Wednesdays 3:00—4:30 PM	Science Center 240

Welcome to CS31!This course is a broad introduction to computer science that focuses on how a computer works and how programs run on computers. We examine the hardware and software components required to go from a program expressed in a high-level programming language like C or Python to the computer actually running the program. This course takes a bottom-up approach to discovering how a computer works, and introduces parallel and distributed computing with a specific focus on parallelism for multicore and other shared memory systems. Topics include theoretical models of computation, data representation, machine organization, assembly and machine code, memory, I/O, the stack, the operating system, compilers and interpreters, processes and threads, and synchronization. In addition to parallel programming, we will discuss parallel computers and system-level support for parallel computing. Prerequisite: Completion of CS21 or its equivalent.

The course is composed of the following:

• Readings: The readings serve as a first exposure to new topics, where students learn the basics of the material.
• Class meetings: The classroom material will cover the difficult concepts and facilitate student discussions.
• Labs: There are several lab programming assignments (in C) that will explore various aspects of systems programming.
• Exams: There is a midterm exam and a final exam (both closed-book) covering the material in the class meetings and labs.

Textbook & Clicker:

Rather than requiring a textbook, we're going to use readings from the web as our introduction to new material. The textbook we've used in the past for this course is: Computer Systems: A Programmer's Perspective by Bryant and O'Hallaron (Second edition: 2/E CS:APP2e). It's a great reference, and I recommend it as a supplemental source of information, if you're interested. I will list corresponding sections for this book, when applicable.

This course will use iClickers to facilitate feedback and discussion during class. Clickers may be purchased at the college bookstore or online. Please register your device as soon as you get it. Registering allows me to give you credit for quizzes and class participation. We will begin using clickers for credit at the start of week 2!

Goals for the course:

By the end of the course, we hope that you will have developed the skills to:

• Implement programs in the C programming language.
• Organize and express data in a variety of formats (integers, strings, etc.).
• Characterize the execution of a program on the OS and underlying hardware.
• Translate between high-level language constructs and low-level assembly instructions.
• Analyse the systems-related costs associated with application performance.
• Evaluate OS abstractions and apply them in programs.
• Classify storage devices and their performance according to their role in the memory hierarchy.
• Debug and examine applications using GDB and Valgrind.
• Desing and implement parallel solutiosn to programming problems that require synchronization.

Schedule

This is a tentative schedule; it may change as we go. You should read the assigned sections before class to prepare for the reading quiz. All readings refer to the Bryant and O'Hallaron textbook unless otherwise indicated (e.g., there's a link to some other source).

WEEK	DATE	ANNOUNCEMENTS	TOPIC & READING	ASSIGNMENTS
1	Jan 22	Class Audio	Course Introduction No Readings.	No Lab
	Jan 23	Lab Audio	Lab, Week 1	Lab 1
	Jan 24	Class Audio	Data Representation Reading: Binary and Data Representation Read Sections: Introduction, Number Bases and Unsigned Integers, and Converting Between Bases The readings are password protected. Please find instructions to access the readings on Piazza.
2	Jan 29	Class Audio	Binary Arithmetic Reading: Signed Binary Integers Binary Integer Arithmetic, Integer Overflow Textbook (supplemental): 2.1.8, 2.1.10, 2.2.3, 2.3-2.3.1, Types (Supplemental) Why the Negation Shortcut Works
	Jan 30	Lab Audio	Lab, Week 2	Lab 2
	Jan 31	Class Audio Drop/Add ends (Feb 02)	Introduction to C Programming Reading: C for Python Programmers (Sections 1.5 - 2.5)
3	Feb 05	No Audio	Digital Circuits Reading: Basic Logic Gates and Digital Circuits up to Storage Circuits Textbook (supplemental): 1.4.1, 4.2 - 4.2.4
	Feb 06	Lab Audio	Lab, Week 3	Lab 3
	Feb 07	Class Audio	Digital Circuits, Cntd. Reading: Computer Architecture, Origins of Modern Computing and, Building a Processor.
4	Feb 12	Class Audio	ISAs and Assembly Reading:Diving into Assembly, Sections 6, 6.1, 6.2, 6.3 Textbook (supplemental): 3.0, 3.2
	Feb 13	Lab Audio	Lab Week 4
	Feb 14	Class Audio	ISAs and Assembly, Cntd. Reading:Functions in Assembly, Conditional Control and Loops Textbook (supplemental): 3.4 - 3.4.2, 3.6 - 3.6.2.
5	Feb 19	Class Audio	Pointers and Memory Reading: The 5-minute guide to C pointers, A Deeper Dive into C, Program Memory and Scope, C Pointer Variables
	Feb 20	Lab Audio	Lab, Week 5	Lab 4
	Feb 21	Class Audio	Pointers and Memory, Cntd. Reading: Pointer Arithmetic (skip "Two dimensional arrays" and "Pointer subtraction") and malloc & free. Textbook (supplemental): 3.5.1, 3.8.2, 9.9.1-9.9.2, 9.11 - 9.11.2, 9.11.7 - 9.11.10.
6	Feb 26	Class Audio	Functions and the Stack Reading: Functions, Data Movement, and Functions in Assembly
	Feb 27		Lab, Week 6	Lab 5
	Feb 28	CLASS CANCELLED	CLASS CANCELLED
7	Mar 05	Class Audio	Functions and the Stack, Cntd. Reading: From x86 Assembly Guide, read about the call and ret instructions and the subsequent "Calling Convention" section - scroll down a little to view.
	Mar 06		Midterm Q&A, Work on Maze Lab.
	Mar 07	Midterm Exam
	Mar 12	Spring break
	Mar 13
	Mar 14
8	Mar 19	Class Audio	Functions and the Stack, Cntd. Reading: From x86 Assembly Guide, read about the call and ret instructions and the subsequent "Calling Convention" section - scroll down a little to view.
	Mar 20	Lab Audio	Lab, Week 8	Lab 6
	Mar 21	Class Audio	Arrays, Structs, and Pointers. Reading: Arrays in C, The String Library, Structs.
9	Mar 26	Class Audio	Arrays and Structs Contd.
	Mar 27		Lab, Week 9	Lab 7
	Mar 28	Class Audio CR/NC and Withdraw deadline (Mar 30)	Storage and the Memory Hierarchy Reading: Introduction, Storage Devices, Memory Hierarchy.
10	Apr 02	Class Audio	Caching Reading: CPU Caches up to Set Associative Caches Textbook (supplemental): 6.3 - 6.4.4
	Apr 03	Lab Audio	Lab, Week 10 (Link to Lab Week08)	Lab 8
	Apr 04	Class Audio	Caching, Cntd. Reading: Set Associative Caches
11	Apr 09	Class Audio	Operating Systems and Processes Reading: Operating Systems, How an OS works.
	Apr 10		Lab, Week 11
	Apr 11	Class Audio	Operating Systems and Processes cntd. Reading: Processes, up to the first exercise.
12	Apr 16	Class Audio	Parallel Applications and Threading Reading: Shared Memory, Programming Multi-core systems, POSIX Threads
	Apr 17		Lab, Week 12	Lab 9
	Apr 18	Class Audio	Parallel Applications and Threading Contd. Reading: Synchronizing Threads Textbook (supplemental): 12.7.4-12.7.5. #
13	Apr 23	Class Audio	Race Conditions and Synchronization Reading: Mutual Exclusion, Semaphores, Barriers and Conditional Variables.
	Apr 24		Lab, Week 13
	Apr 25	Class Audio	Race-Conditions-and-Synchronization cntd. (Parallel applications with pthreads) Reading: No reading quiz. Review previous readings.
14	Apr 30	Class Audio	Virtual Memory Reading: Virtual Memory (up to Virtual and Physical Addresses in Paged Systems). Textbook (supplemental): 9.0-9.2, 9.5, 9.6.0.
	May 01		Lab, Week 14
	May 02	Class Audio	Virtual Memory, Cntd. Reading: Virtual and Physical Addresses in Paged Systems, Paging Implementation, Memory Efficiency.
	May 12	Final Exam 9:00am-12:00pm SCI 199

Lab Policy

This course features regular lab assignments that account for the largest component of your course grade. Lab attendance is required by all students, unless you have already completed and submitted the lab assignment for the week. Additionally, the cs labs are open 24 hours a day, 7 days a week for you to use for CS43 lab assignments. While you must attend the lab session for which you are registered, you may optionally attend additional lab sessions, provided space is available. In case of space constraints, students registered for the lab will have seating priority.

Lab assignments will typically be assigned during the lab sections on Friday will generally be due by midnight on Thursday 1-2 weeks later. You are strongly encouraged to start early!

Even if you do not fully complete an assignment, you should submit what you have done to receive partial credit.

Accessing the CS labs after hours

You can use your ID to gain access to the computer labs at nights and on the weekends. Just wave your ID over the onecard reader next to the lab doors. When the green light goes on, just push on the door handle to get in (the door knob will not turn). If you have issues with the door locks, send an email to local-staff@cs.swarthmore.edu. If the building is locked, you can use your ID to enter the door between Martin and Cornell library. For this class, your ID will give you access to the labs in rooms SCI 238, 240, 256, and Clothier basement.

Ninjas

The CS 31 Ninjas are student mentors who will assist in class/labs and run evening study sessions. You are encouraged to participate in Ninja evening study sessions to get friendly assistance on lab assignments and help with preparing for exams.

Weekly Evening Ninja Session: Sundays, 7:00 PM - 11:00PM

The CS 31 Ninjas: Sally, Shayne, Greg, Kevin

Ninja Coordinator: Lauri Courtenay (SCI 257)

Grading

Grades will be weighted as follows:

35%	Lab assignments
30%	Final Exam
25%	Midterm Exam
5%	Reading Quizzes (I will drop your three lowest quizzes.)
5%	Class Participation

Absence / Assignment Extension Policy

To help with cases of minor illnesses, athletic conflicts, or other short-term time limitations, we will drop your three lowest reading quizzes and participation grades. You are still responsible for the material, and you should review any missed materials via the class recordings as soon as you can.

You must submit your assignments electronically by pushing to your assigned git repository. You may push your assignment multiple times, and a history of previous submissions will be saved. You are encouraged to push your work regularly.

All students start the course with two "late assignment days" to be used at your discretion, with no questions asked. To use your extra time, you must email your professor after you have completed the lab and pushed to your repository. You do not need to inform anyone ahead of time. When you use late time, you should still expect to work on the newly-released lab during the following lab section meeting. The professor will always prioritize answering questions related to the current lab assignment.

Your late days will be counted at the granularity of full days and will be tracked on a per-student (NOT per-partnership) basis. That is, if you turn in an assignment five minutes after the deadline, it counts as using one day. For partnered labs, using a late day counts towards the late days for each partner. In the rare cases in which only one partner has unused late days, that partner's late days may be used, barring a consistent pattern of abuse.

If you feel that you need an extension on an assignment or that you are unable to attend class for two or more meetings due to a medical condition (e.g., extended illness, concussion, hospitalization) or other emergency, you must contact the dean's office and your instructors. Faculty will coordinate with the deans to determine and provide the appropriate accommodations. Note that for illnesses, the College's medical excuse policy, states that you must be seen and diagnosed by the Worth Health Center if you would like them to contact your class dean with corroborating medical information.

How to Succeed in CS 31

• Read the material before you come to class.
  Don't worry about total comprehension, but at least get a feel for what we will be covering that week. If you have some understanding of the material coming into class, it will be easier for you to ask questions during class, rather than later when help may not be available.
• Attend class and participate in discussions.
  In class, we'll cover new topics and dig into the more challenging details of the material. Class discussions are a critical part of the learning process, as these exercises give you immediate experience with the material we are covering. Also, we'll have frequent reading quizzes, so you need to be present!
• Ask questions if you don't understand.
  This means both during class and while doing lab assignments. This class continually builds on previous material, so if you don't understand something one week, it will continue to be a problem the next week, and the week after that, and so on. If you need help, ask your classmates (make sure you have read the "Academic Integrity" section below first), post on Piazza, or come talk with me during my office hours.
• Start the lab assignments early.
  I realize this one is not always easy to do, but if you can get in the habit of doing this, you will be much better off. If you get stuck early (i.e., not two hours before it is due), there will be time to look for help. In addition, if you start early enough, you can take a break, go do something else, and come back later. I find I always have at least a few new ideas when I come back to a problem after a break. If you wait until the last minute, you can't do this.
• Practice, practice, practice.
  The only effective way to learn the material and pass the quizzes and exams is to consistently do the labs. Finish all of the assigned programs (and do some extras, for fun!). Even if you don't get them done on time, they will still help you learn the material.
• Seek help early and often.
  Because course material builds on previous material, it is essential to your success in this class that you keep up with the course material. If you are having difficulty with a programming assignment, if you didn't follow something covered in class, if you feel you need some extra help understanding or practicing some of the course material, or if you just want to discuss something from a class, an assignment, or the text, please come to my office hours.
• Attend CS43 Labs.
  Lab attendance is required, and the labs constitute the largest portion of your grade. You should be there!

Academic Integrity

Academic honesty is required in all your work. Under no circumstances may you hand in work done with (or by) someone else under your own name. Your code should never be shared with anyone; you may not examine or use code belonging to someone else, nor may you let anyone else look at or make a copy of your code. This includes, but is not limited to, obtaining solutions from students who previously took the course or code that can be found online. You may not share solutions after the due date of the assignment or make them publicly available anywhere (e.g. public GitHub repository).

Discussing ideas and approaches to problems with others on a general level is fine (in fact, we encourage you to discuss general strategies with each other), but you should never read anyone else's code or let anyone else read your code. All code you submit must be your own with the following permissible exceptions: code distributed in class, code found in the course text book, and code worked on with an assigned partner. In these cases, you should always include detailed comments that indicates on which parts of the assignment you received help, and what your sources were.

Failure to abide by these rules constitutes academic dishonesty and will lead to a hearing of the College Judiciary Committee. According to the Faculty Handbook: "Because plagiarism is considered to be so serious a transgression, it is the opinion of the faculty that for the first offense, failure in the course and, as appropriate, suspension for a semester or deprivation of the degree in that year is suitable; for a second offense, the penalty should normally be expulsion."

The spirit of this policy applies to all course work, including code, homework solutions (e.g., proofs, analysis, written reports), and exams. Please contact me if you have any questions about what is permissible in this course.

Exam Integrity

Students must strictly adhere to the following policy, which applies to all exams taken in a Computer Science course at Swarthmore:

Exam takers must place all non-essential items at the front of the room (or other designated area). Unless otherwise permitted, students may not have any electronic devices or course materials in their possession during the entirety of the exam. This includes cell phones, tablets, laptops, smart watches, course notes, articles and books, among others. These items should be placed at the front of the room near the proctor. If you need to leave the room during the exam, you must obtain permission from an instructor first. Any non-permitted discussion or aide in regards to exam material will result in immediate forfeiture of the exam and a report to the College Judiciary Committee. Please discuss any concerns or accommodations with your instructor prior to starting the exam.

Academic Accommodations

If you believe that you need accommodations for a disability, please contact the Office of Student Disability Services (Parrish 113) or email studentdisabilityservices@swarthmore.edu to arrange an appointment to discuss your needs. As appropriate, the office will issue students with documented disabilities a formal Accommodations Letter. Since accommodations require early planning and are not retroactive, please contact them as soon as possible. For details about the accommodations process, visit the Student Disability Service Website.

You are welcome to contact me privately to discuss your academic needs, but all disability-related accommodations must be arranged through the Office of Student Disability Services. To receive an accommodation for a course activity you must have an official Accommodations Letter and you need to meet with me to work out the details of your accommodation at least two weeks prior to any activity requiring accommodations.

External Links

Links that are related to the course may be posted here. If you have suggestions for links, let me know.

• Tips for Reading CS Textbooks
• Tools for examining system state.
• Phases of Compilation and Tools for examining .o and a.out files

C Programming

• Introduction to C Programming for CS31 Students
• C for Python Programmers
• The Descent to C

Unix Help Pages

• Tia's Unix Help Pages and Links
• Useful Unix Commands
• Remotely Connecting to CS
• CS Department's Help Pages

Assembly

• IA32 Cheat Sheet by Julie Zelenski
• IA32 Stack Frame
• x86 Assembly (Wikibooks)
• Textbook Website