15-213 Notes

213 reference sheet

Main

1. Why Systems Knowledge

   Why Systems Knowledge

   #lecture note based on The Reasons Looking underneath abstractions Abstractions have limit Become a better programmer by understanding what things are compiled to Great...

   6/24/2025

2. Data Representation as Bits

   Data Representation as Bits

   #lecture note based on Bits Either 0 or 1? That's abstraction of electronic implementation. Votage isn't discrete. Representations - Bits are just...

   6/24/2025

3. Memory Layout

   Memory Layout

   #lecture note based on Overall Memory Layout (for a process) A process's virtual memory, assuming it's running one thread. 50 Bytes in Memory Integers...

   6/24/2025

4. Assembly and Machine Programming

   Assembly and Machine Programming

   #lecture note based on Abstraction Level Overview A bit of history ... (whatever) Intel x86! - Complex Instuction Set Computer (CISC) - lots...

   6/24/2025

5. Data in Machine Programming

   Data in Machine Programming

   #lecture note based on We're interested in storing some structured data, such as struct or array, but memory is just...

   6/24/2025

6. Machine Programming Vulnerabilities

   Machine Programming Vulnerabilities

   #lecture note based on Attacks by overwriting memory buffer overflow / stack smashing attack - big cause of security vulnerability. If...

   6/24/2025

7. Memory Hierarchy

   Memory Hierarchy

   #lecture note based on Overview For many years, hardwares are optimised with some memory hierarchy and software designed to use them....

   6/24/2025

8. Code Optimisation

   Code optimisation

   #lecture note based on Overview Goals minimise num of instructions less instructions less slow calculations (multiplication, divsion) minimise memory wait time what to go in register...

   6/24/2025

9. Dynamic Memory Allocation

   Dynamic Memory Allocation

   #lecture note based on Allocation and freeing malloc ~ ~ ~ There are just things we don't know the size of....

   6/24/2025

10. Linking

    Linking

    #lecture note based on "The most useless useful lecture... Almost nothing in this lecture matter for the course... however this...

    6/24/2025

11. Virtual Memory

    Virtual Memory

    #lecture note based on Notice: lots of processes can run at the same time, yet their memory addresses don't overlap... Goal:...

    6/24/2025

12. Processes

    Processes

    #lecture note based on History: human used to manage processes, but in 70s they wanted multiple people to connect by...

    6/24/2025

13. Shell

    Shell

    #lecture note based on A programme that runs programmes on behalf of user. Usually console based, but it could be...

    6/24/2025

14. Exceptional Control Flow

    Exceptional control flow

    #lecture note based on We don't yet have a way to control flow if... say... the printer is on fire....

    6/24/2025

15. System-level IO

    System-level I/O

    #lecture note based on System level IO - much lower level than fopen, fputs, fclose, etc. Those are just higher...

    6/24/2025

16. Network Programming

    Network Programming

    #lecture note based on Network - system of boxes and wires LAN local area WAN wide area SAN storage area MAN metropolitan ... internet - interconnect...

    6/24/2025

17. Concurrent Programming

    Concurrent Programming

    #lecture note based on Classical problems in concurrent programmes Race - what happens when scheduler do arbitrary things e.g. multiple threads incrementing...

    6/24/2025

Misc

• Design and Debugging
• GDB
• printf directives
• Useful Systems Programming Commands

Misc 2

• volatile means not in register, not not in main memory
• Magic number - use of one number in one place magically make other code work or not work
• char payload[0] is zero length array but means flexible size
• offsetof(struct, member) is in C standard where compiler tells you offset to field in struct
• Technically gcc is not compiler. It launches the compiler
• static means it’s there but don’t tell other module
• telnet to test server. it just sends ascii