- Preparing for Class Meetings
- Material by Topic
- Computational Building Blocks
- Hardware-Software Interface
- Abstractions for Practical Systems
Electronic options are available for all required sources. At least one physical copy of each text is also available in the physical SCI L037 CS Systems Lab for use within the CS department area. Please use them in the data lab area and return them to the shelf when you are done.
We use one primary textbook extensively:
- CSAPP 3e (Wellesley online access):
Computer Systems: A Programmer’s Perspective, 3/E. (3rd edition, significant changes since 2nd)
Bryant and O’Hallaron, Pearson, 2016. ISBN-13: 9780134092669.
- We need the 3rd edition. See the errata.
- Unfortunately, the library is not able to acquire an electronic
version, but there are several options to access the book,
including, but not limited to:
- If you prefer physical books, paperback copies are available for much less than the hardcover version. “Global” 3rd editions mostly work, but have some additional errors (not listed on the errata page).
- 6 months of access to an electronic version is available for $35.
- During difficult pandemic circumstances, we have scans of the relevant excerpts available for CS 240 students (Wellesley ONLY). Being scans, these excerpts are not quite as good quality as some other electronic or paper options.
- Please contact the instructors if none of the available options work for you.
Other textbooks are used during the first part of the course:
- DDCA (Wellesley online access):
Digital Design and Computer Architecture.
Harris and Harris, Morgan Kaufmann, 2007.
We recommend a good reference on the C programming language. Here are a couple solid options:
- Essential C (PDF)
Nick Parlante, 2003. Stanford University.
The C Programming Language, 2nd edition.
Kernighan and Ritchie, Prentice Hall, 1988. ISBN-13: 978-0131103627, ISBN-10: 0131103628.
Additional materials will be posted directly on the course website.
Preparing for Class Meetings
Before each class meeting, complete the required preparation steps listed in the topics for the day. Preparation varies from day to day, but usually consists of some combination of watching videos, reading, or trying small exercises, and asking or answering questions on Zulip. Expect the preparation to take more than a few minutes. Synchronous class activities will build on ideas in preparation material.
How to watch videos for CS 240
Many topics will have videos attached. When asked to watch these videos for preparation, or if you use them for reference at any time:
- You can view them on YouTube (nocookie version without tracking) or download/watch the MP4 files directly.
- Take notes like you would in class.
- You might find it helpful to download a copy of the slides to follow along or take notes.
- It’s fine to pause and take breaks whenever you want!
- You do not need to watch all the videos from one topic or even all the videos assigned for one day of preparation in one sitting. The videos are usually broken up into chunks usually between 5 and 15 minutes length, occasionally a little shorter or longer.
- When the talking head says to “try this,” pause the video to freeze the talking head in a bizarre pose, then actually try the example, just like you would in class when we do an exercise together.
How to read for CS 240
Effective reading for computer science courses demands a staged approach. Aim for two types of reading:
- Do an initial reading in preparation for the class when the topic is scheduled.
- Revisit the reading later for deeper details or reference.
Before class, do an initial reading of the any reading material assigned as preparation for class.
Do not worry about understanding every last detail.
Do aim to acquire:
- A big-picture view of the pieces we will consider about this topic.
- Some familiarity with basic mechanics of the ideas introduced.
To help distinguish core points from secondary concerns during initial reading, each reading is listed with one of two style directives:
- Read means read for enough detail to do indicated reading exercises. If you do get stuck or confused by some details, do not worry. Make a note and move on. If we do not clear up your confusion in class, ask a question or come to office hours.
- Skim means read for high-level ideas. Perhaps pick out a couple details that look interesting and accessible. Do not spend much time trying to understand all the details before moving on.
Learning how to identify essential vs. inessential details during a first reading is an important skill that takes time to develop. As the semester progresses, we will leave more of this to you.
Readings assignments may indicate specific exercises to try as you read before class. These are typically practice problems from the reading.
- Try means work through enough of the exercise to see how the basics work. Do not feel obligated to finish every example. Do what is useful to you. (Do not submit anything.)
We typically highlight exercises that practice mechanics. Feel free to try other practice problems as well. They may require more time and critical thinking. We will explore such interesting examples in class.
After class, revisit readings in more depth and try more practice problems to work out details as needed.
More advice for reading
Our main text (CSAPP) sometimes goes into more detail than we will cover, so learning to “read around” extra detail is a useful skill, especially in your pre-class reading.
When reading from CSAPP:
- “Asides” are optional. If you read them, skim them.
- “New to C?” blocks can be useful, but usually only if they are short.
- Some sections (e.g., 2.2 - 2.4 on integer and floating point representations) can be too dense for our purposes. We try steer you around them, but if you find other things getting dense, flip to another reading or just make a note and jump ahead.
- This book really shines with later material about machine/assembly language, caching, memory management, and other topics. We use it intermittently in the first section of the course, then extensively for the latter two.
Tia Newhall (Swarthmore College) has more good advice on reading computer science textbooks.
Material by Topic
This list of topics includes:
- Topics covered in class meetings, with preparation directions and listings of all lecture materials, associated readings, and activities.
- +Optional items that offer opportunities to explore further, but are not required.
Welcome to CS 240! Labs and lectures–including the first lab and lecture this week–are generally preceded by some asynchronous preparation to allow us to use meeting time productively. Please complete these steps in advance.
Before your first CS 240 lab:
- Watch video 1 for this topic in the “Materials” section just below.
- Complete the first lab assignment by watching this playlist of three “Computer Science Crash Course” videos about computing history and basic electronic building blocks for digital computation. For following labs, lab preparation and materials will be provided separately by Jean on the lab page.
- Bookmark and tour the main CS 240 course website, your central source for all course info and materials, and review course logistics and policies.
Before your first CS 240 lecture:
- Watch videos 2-3 for this topic (listed just below, in “Materials”) to wrap up course motivation.
- Prepare for topics listed on the first day of lecture on the course calendar. Each lecture topic on the calendar links to a section on this page with preparation steps to complete ahead of lecture and materials for the topic.
- Sign up for the CS 240 Zulip using the invitation link in the initial course email message that brought you here. Course communication will happen there (not email).
Before the end of this week:
- Post a brief message in the intros topic of the #community stream on the
CS 240 Zulip to
introduce yourself with:
- your name;
- your pronouns; and
- something that brought you joy since the end of last term/semester.
- Skim reading 3 (listed just below, in “Materials”) for general background on the working of modern computers.
Questions? Post them on Zulip.
Videos: ☰ yt playlist The Plan
- Review basic digital logic gates and Boolean algebra notation from lab.
- Reading 1 (below)
- Reading 1 (below)
- Watch videos or read:
- Videos 1-5 (below)
- Readings 2-3 (below)
The YouTube viewing option may be useful if you wish to watch faster or slower.
- Follow up with videos on any remaining topics we did not cover in class.
- Review extra detail in Readings 3-4 as needed.
- Basic Bit Exercises
- Basic Bit Exercises SOLUTION
- Mask and Shift Exercises
- Mask and Shift Exercises SOLUTION
- +Supplemental Bits Practice
- +Supplemental Bits Practice SOLUTION
Videos: ☰ yt playlist Data as Bits
- ▸ mp4 yt Positional Number Representation and Binary
- ▸ mp4 yt Conversion Between Binary and Decimal
- ▸ mp4 yt Binary Arithmetic
- ▸ mp4 yt Bytes and Hexadecimal
- ▸ mp4 yt Fixed-size Data Types
- ▸ mp4 yt Bitwise Operators
- ▸ mp4 yt Bitwise Operator Practice
- ▸ mp4 yt Bit Sets
~aset complement example should be
~b. The slides have been updated.
- ▸ mp4 yt Boolean Logical Operators
- ▸ mp4 yt Card Encoding Ideas
- ▸ mp4 yt Compact Encodings with Bit Fields and Masks
- Mask Practice (see exercise above)
- ▸ mp4 yt Bit Shifting
- ▸ mp4 yt Shift-and-Mask Puzzle
- ▸ mp4 yt Shift-and-Mask Review
- Preparing for Class Meetings in CS 240, including tips for effective watching and reading.
- Binary and hexadecimal number systems
- Information as bits + context
- Bitwise Boolean algebra and bit manipulation
- Videos 1-4. Short on time? Skip videos 2 and 4.
- Follow up with videos on any remaining topics we did not cover in
class, most likely including:
- Shifts as arithmetic (video 11) and how to compose them to accomplish general multiplication (videos 12-14).
- Converting between types (video 15).
- Complete the Fixed-Sized Integer Exercises and review their solutions. These are excellent practice to prepare for the two’s-complement puzzles in the Bits assignment. Post any questions on Zulip.
- Review any other videos or readings as needed.
- Fixed-Size Integer Exercises
- Fixed-Size Integer Exercises SOLUTION
- +Supplemental Integers Practice
- +Supplemental Integers Practice SOLUTION
Videos: ☰ yt playlist Integer Representation
- ▸ mp4 yt Unsigned Representation, Modular Arithmetic, Overflow
- ▸ mp4 yt Sign-Magnitude Representation
- ▸ mp4 yt Two's Complement Representation
- ▸ mp4 yt Two's Complement Examples
- ▸ mp4 yt Two's Complement Addition
- ▸ mp4 yt Two's Complement Overflow
- ▸ mp4 yt Overflow and Reliability
- ▸ mp4 yt Two's Complement is Awesome, Complement Rules
- ▸ mp4 yt Deriving Two's Complement
- ▸ mp4 yt Sign Extension
- ▸ mp4 yt Shift Arithmetic
- ▸ mp4 yt Shift and Add
- ▸ mp4 yt Shift and Add Puzzle Review
- ▸ mp4 yt Muliplication
- ▸ mp4 yt Converting Between Unsigned and Signed Types
Refer to this material only after videos/class. We’d like to introduce signed integer representations before you read about them.
As you read, focus on the positional representation of signed integers more than the mechanics of how to convert from integer representation to the representation you know well.
For the basics, read one of:
- “Twos Complement” section of these notes. Stop at “Floating Point.”
- Fundamentals of Data Representation: Two’s Complement
- CSAPP’s treatment of number representation is more thorough, but
some students find it too dense and prefer to skip some parts.
- Read: CSAPP 2.2 - 2.2.3.
Then, for reference on integer multiplication and division, their relation to bitwise operations, and sign extension:
- Skim Reading 1.
- Follow up with additional detail in Readings 1-2.
- No preparation.
- Review adders (Reading 1).
- Adders, one of:
- Arithmetic Logic Unit (high-level organization), one of:
- DDCA 5.2.2 - 5.2.4 (pages 23-234) up through Ripple Carry Adders (feel free to skim beyond if you are curious)
- Arithmetic Logic Unit sections “Signals” and “Circuit Operation”
We will look at details of a specific ALU design in class.
- Skim Reading 1.
- Skim Reading 2 for a bit more on RAM.
- Latches, Flip-Flops, Registers:
- DDCA 3.0 - 3.2.4 (pages 103-109)
- Note for context: In class, we use the terms leader and follower to describe the component latches of a D flip-flop. This textbook uses a different terminology that has been widely used in the past to describe flip-flops (and a handful of other computer systems concepts that CS 240 does not consider) by analogy to enslavement. We do not use that terminology in class. We ask that you also use the leader/follower terms.
- DDCA 3.0 - 3.2.4 (pages 103-109)
- Random Access memory (basics):
- Read DDCA 5.5 - 5.5.1 (pages 257-262) (ignore Verilog and VHDL). We will cover RAM only briefly.
- Skim one option for Reading 1.
- No preparation.
Read for general organization and design points about instruction set architecture and microarchitecture. We will build our own toy architecture in class and lab.
For Friday before break:
- Videos 1-3. Expect to have some questions. This usually takes some repetition.
For Friday after break:
- Review videos 1-11 if you missed class before break.
- Additional videos or readings for parts we skipped in class.
Videos: ☰ yt playlist Programming with Memory
- ▸ mp4 yt Byte-Addressable Memory
- ▸ mp4 yt Multi-Byte Values in Memory
- ▸ mp4 yt Data, Addresses, Pointers
- ▸ mp4 yt C Variables as Memory Locations
- ▸ mp4 yt C Pointer Primitives
- ▸ mp4 yt C Pointer Example
- ▸ mp4 yt C Arrays
- ▸ mp4 yt C Arrays and Pointers
- ▸ mp4 yt C Pointer Arithmetic
- ▸ mp4 yt C Array Sizing
- ▸ mp4 yt C Array Expression Examples
- ▸ mp4 yt Pointer Exercises Intro
- ▸ mp4 yt C Strings
- ▸ mp4 yt C Strings as
char*and Cursor Pointer Style
- ▸ mp4 yt C
- ▸ mp4 yt Memory Address Space Layout
- ▸ mp4 yt C Memory Allocation with
- ▸ mp4 yt C Arrays of Pointers to Arrays
- ▸ mp4 yt
- ▸ mp4 yt C
scanfand Memory Errors Teaser
- ▸ mp4 yt Why C?
General memory model:
- +Optionally, read: SCO 2.2.2 - 2.2.3, 5.1.2 (stop at “Note that having separate address spaces for instructions and data”)
- Read: CSAPP 2.1.0, 2.1.3 - 2.1.4
Mix and match to start learning about addresses and pointers in C:
- No preparation.
- Video 1 for historical background.
- Additional videos for topics not finished during class.
Videos: ☰ yt playlist x86 Basics
- ▸ mp4 yt Intro and History
- ▸ mp4 yt Registers, Data Movement Instructions, and Memory Addressing Modes
- ▸ mp4 yt Memory Examples
- ▸ mp4 yt Memory Addressing Review
- ▸ mp4 yt Load Effective Address (lea)
- ▸ mp4 yt Procedure Call Stack Basics
- ▸ mp4 yt Arithmetic and Logic Instructions,
- ▸ mp4 yt
- ▸ mp4 yt
- Skim: CSAPP 3 - 3.2
Load Effective Address:
- Read CSAPP 3.5.1
- Videos 1-2 or Readings 1-2
- Review videos 1-4 and the if-else exercises as needed.
- x86 Control Flow If-Else Exercise
- x86 Control Flow Loop Exercise
- x86 Control Flow Loop Exercise SOLUTION
Videos: ☰ yt playlist x86 Control Flow
- ▸ mp4 yt Condition Codes, Comparisons, and Tests
- ▸ mp4 yt Jumps, Translating If-Else, and
- ▸ mp4 yt
absdiffExercise Review, goto, and If Compilation Exercise Setup
- ▸ mp4 yt If Compilation Exercise Review and PC-Relative Addressing
- ▸ mp4 yt Translating Loops
- ▸ mp4 yt Conditional Moves
- ▸ mp4 yt Translating Switch Statements with Jump Tables
- ▸ mp4 yt Translating Switch Statement Cases, Reverse Engineering Switches
Comparisons, Tests, and Jumps
- Skim: CSAPP 3.6.8, 3.6.6
- No preparation.
- Review videos 1-4 or readings 1-2 as needed.
Videos: ☰ yt playlist x86 Procedures, Call Stack
- ▸ mp4 yt The Call Stack Stores Procedure Context
- ▸ mp4 yt Procedure Control Flow Instructions (
ret), Data Flow Conventions, Puzzle Setup
- ▸ mp4 yt Procedure Puzzle Review
- ▸ mp4 yt Procedure and Stack Frame Example
- ▸ mp4 yt Register Saving Conventions, Callee-Save Example
- ▸ mp4 yt Recursion Example
- ▸ mp4 yt Stack Storage Example, Procedure Summary
- Video 1 or reading 1
Note: class will focus on simple arrays and structs (videos 1 and 5-7, readings 1 and 3), leaving nested arrays (videos 2-4, reading 2) for later.
For labs the next week:
- Videos 2-4 or reading 2: two-level arrays and nested arrays.
Videos: ☰ yt playlist Representing Data Structures
- ▸ mp4 yt Simple Arrays
- ▸ mp4 yt Multi-Level Arrays (Arrays of Pointers to Arrays of...)
- In the copyleft example, all occurrences of 4 in the x86 code should be replaced by 8.
- ▸ mp4 yt Row-Major Multidimensional Arrays
- ▸ mp4 yt Row-Major Array Review
- ▸ mp4 yt Structs
- ▸ mp4 yt Struct Alignment
- ▸ mp4 yt Linked List Representation
- No preparation.
Videos: ☰ yt playlist Buffer Overflows
- ▸ mp4 yt Overview
- ▸ mp4 yt Stack Layout and No Bounds Checking in C
- ▸ mp4 yt Example Overview
- ▸ mp4 yt Example 1 - Overwrite Padding (Lucky)
- ▸ mp4 yt Example 2 - Corruption and Segfault
- ▸ mp4 yt Example 3 - Silent Corruption and Arbitrary Code Execution
- ▸ mp4 yt Remote Code Execution and Avoiding Vulnerabilities
- If you have not yet reviewed two-level arrays and nested arrays, review video 3 or reading 2 from the data structures topic.
- Cache: Videos 1-3 or start Reading 1
- Review videos 1-11 and 13 / Reading 1 as needed.
Videos: ☰ yt playlist Memory Hierarchy, Cache
- ▸ mp4 yt Motivating Example
- ▸ mp4 yt Cache Overview
- ▸ mp4 yt Cache Mechanics
- ▸ mp4 yt Locality
- ▸ mp4 yt More Locality Examples
- ▸ mp4 yt Cache Performance and the Hierarchical Memory Design
- ▸ mp4 yt Cache Organization
- ▸ mp4 yt Cache Blocks
- ▸ mp4 yt Direct-Mapped Cache Placement Policy and Cache Tags
- ▸ mp4 yt Address Fields
- ▸ mp4 yt Why Not Another Direct Mapping (Aside)
- ▸ mp4 yt Cache Puzzle 1
- ▸ mp4 yt Cache Conflicts and Associative Cache Placement Policies
- ▸ mp4 yt Cache Puzzle 2
- ▸ mp4 yt General Cache Dimensions and Organization
- ▸ mp4 yt General Cache Read Mechanics
- Cache Analysis Example 1: Spatial Locality in Direct-Mapped Caches
- Cache Analysis Example 2: Cache Conflicts in Direct-Mapped Caches
- Cache Analysis Example 3: Cache Conflicts Resolved by Associativity
- Types of Cache Misses
- Cache Write Policies
- Cache-Friendly Code and Summary
Watch videos instead of Tuesday 30 November lecture.
Per College public health policy, classes during Monday 29 November through Wednesday 1 December will be remote, not in person.
CS 240 will not hold synchronous remote lectures on Tuesday 30 November. Instead, please watch the full set of videos for this topic at any time before your lab meeting this week. Post questions on Zulip.
Labs will be synchronous (watch for details) and will practice this material as part of launching the final assignment.
- Videos 1-11
- Optionally, readings 1-3
Videos: ☰ yt playlist Memory Allocation
- ▸ mp4 yt Allocator Basics
- ▸ mp4 yt Determining Block Size
- ▸ mp4 yt Block Format and Heap Layout
- ▸ mp4 yt Implicit Free List Search
- ▸ mp4 yt Implicit Free List Allocation and Splitting
- ▸ mp4 yt Implicit Free List Freeing and Coalescing
- ▸ mp4 yt Explicit Free Lists
- ▸ mp4 yt Explicit Free List Search, Allocation, and Splitting
- ▸ mp4 yt Explicit Free List Freeing and Coalescing
- ▸ mp4 yt Seglists and Allocation Summary
- ▸ mp4 yt Malloc Assignment - Block Format
- Note that this video was recorded in Spring 2020 before the "Remembrallocator" title for the Malloc assignment was retired along with the past course assignment theme.
- Read: CSAPP 1.7, 8.2 - 8.4
+Shells, Signals (optional)
+Optional: This topic is an optional opportunity for further depth or exploration.
- Read: CSAPP 9.0 - 9.7