Linux System Programming Techniques & Concepts

There are already innumerable courses/tutorials on the internet/Udemy which teach almost every aspect of C programming language. All those courses sound the same, talk the same and deliver more or less the same knowledge. How is this course different from others?

The intention of this course is to make you ready for System programming Technical interviews, interview level – from Beginner to Intermediate. This course is for (future) Developers, not for testers or System Administrators.

I choose to create this course to fill the gap between novice/beginner and intermediate/Advanced Programmers. This course assumes that you are at least above average in programming (in any programming language, but preferable in C/C++) – know memory allocations, all kinds of loops, function calls, pointers etc.  In this course, I won’t teach C/C++ (there are already many courses on it online) but would teach programming techniques and low-level details regarding how C program works behind the scenes – All topics are very important from an interview point of view. My Target is to grow this course into Linux/C Bible.

Yet, I always feel, you need to outsmart your fellow colleagues in this era of stiff competition, and therefore, I tried this attempt to present you the wisdom and knowledge which is of utmost importance for a programmer. I have seen though students could write good C/C++ programs, yet they lack the clarity on how one should write better organized, Manageable, extensible, and programmable codes in the form of libraries. For example, Students are too good at competitive programming, yet do not know how to write a simple Makefile, the reason being, Academics do not teach and students do not care to learn.

In this course, I will cover the topics related to creating Linux System Libraries (release 1) with Advanced language-agnostic Programming Concepts (release 2) which can be well applied if you happen to become a programmer in other languages tomorrow.

The Concepts like MultiThreading, Thread-Synchronization, Socket Programming, IPCs, etc demand a separate course on each topic altogether. Currently, I have a course on IPC, pls check it out. These topics are out of scope for this course.

The Course shall be delivered into two Releases :

     Release 1 Building and Managing a Library:  This covers the basics regarding how one should create and organize his code as a Library.

     Release 2 Memory Management Concepts:  This covers Advance concepts on Linux Memory Management specifically. Please check the Table of Contents for more info.

Why you should *NOT* do this course?

1. Please Excuse this course if you are the ultimate beginner in C programming !!

2. There is no point of doing this course if you don’t like hitting the keyboard, and are lazy enough to watch lecture VDOs only

3. If you want everything cooked and served on your plate.

Course Pre-requisite :

• Above Beginners Level in C/C++ programming
• Good to have basic OS knowledge
• Zeal to excel and Code

No Third-Party libraries

Whatever logic you implement, you need to implement it from scratch. Like all my other courses, this course does not suggest taking the help of any third-party library to get the jobs done. The use of external libraries completely defeats the purpose of the course.

Warning: This course has auto system-generated subtitles which may not be perfect. Please disable subtitles at your convenience.

Curriculum :

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Release 1 Building and Managing a Library

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Section 1 : Introduction to Libraries

• What is Library
• Relationship between Library and Application
• Ex : Doubly linked list as a Library
• Quick Compilation Steps
• Summary

Section 2 : Header Files

• Relationship between Source and header files
• Text Substitution Method
• Text Substitution Method – Example and Demo

Section 3 : Preprocessing Directives

• Problem of Duplicate inclusion of Hdr files
• Pre-processing Directives
• Solution to Duplicate inclusion of Hdr files

Section 4 : Correct way of Using Structures and Functions

• Structures – Define and Use thumb Rule
• Functions – Declare and Use thumb rule
• The problem of Recursive Dependency
• A solution to Recursive Dependency

Section 5 : Creation of Static and Dynamic Libraries

• Resuming with Doubly Linked List Library
• Quick Creation of Static and Dynamic Libraries
• Linking with Static Library
• Linking with Dynamic Library

Section 7: Understanding four stages of Compilation

• Four stages of C/C++ Compilation
• How Dynamic Library works ?
• Dynamic Linking : Linking with Dynamic Library
• Comparison – Static Vs Dynamic Linking

Section 8 : Building using a Makefile

• What are Makefiles and why do we need it
• Functions of Makefile
• Makefile Dependency tree
• Steps of Writing a Makefile
• Assignment on Makefile

Section 9 : Run-time Programmable libraries

• What are Programmable Libraries?
• Steps to Program the libraries
• Registering of the callbacks with Libraries
  • key_match callback
  • comparison_fn callback
• Delegation of Application-specific operations to Libraries

Section 10 : Writing Iterators using Macros

• What are Iterative Macros ?
• Why we need Iterative Macros ?
• How to Write Iterative Macros – For Trees and Linked Lists
• Exercises

Section 11 : Glue Based Libraries and Data structures

• What are the Glue Based Libraries?
• Introducing Glthreads – A Glued LinkedList
• Glthreads Vs Traditional Linked List
• Structure field offset
• GLThread Operations
• Code Walk
• GLThread Benefits

Section 12 : Bit Level Programming

• Logical Operators
• Implementing BIT manipulating C macros
• Using Enums as Bits
• Bit Pattern Matching
• BitMaps

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Release 2 Memory Management Concepts

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Section 13 : Memory Layout of Linux Process

• Virtual Memory Basics
• Memory Layout of Linux Process
• Example: Memory Layout of Linux Process
• Exercise on size command

Section 14 : Stack Memory Management

• Stack Memory Basics and Contents
• Stack-Overflow and Prevention
• Stack Memory Corruption
• Common Cpu Registers
• Procedure Call Mechanism – Step by Step
• Purpose of Base Pointer register (ebp)
• Procedure Return Mechanism – Step by Step
• Lab session

Section 15 : Heap Memory Management

• Introduction and Goals
• How Malloc Works
• Top of Heap Memory region – break pointer
• Heap Memory Mgmt Sys Calls – brk and sbrk
• Meta and Data Blocks
• How free() works
• Block Splitting
• Block Merging
• Memory Illness – Problem of Fragmentation

Section 16 : Concept of Paging

• Introduction to Paging
• Byte Addressable Memory
• 32 bit and 64 bit Machine Architecture
• Address Bus and Data bus
• Physical Vs Virtual Address
• Physical Memory Frames
• Virtual Address Composition
• Page Table
• Paging In Action
• Shared Physical Memory

Section 17 : Multilevel Paging

Section 18 : Demand Paging

Section 19 : Memory Management for Multi-threaded Process

The intention of this course is to make you ready for System programming Technical interviews from beginners to upto 8-9 yrs of experience.

Q. What are the frequently asked questions by interviewers in a technical round when someone writes C/C++/System Programming language on their resume?

Answer : If i am interviewer, what questions i would ask depends on his no of years of experience in C.

1–3 yrs of experience — I would have asked:

1. Double pointers
2. design a Macro to return the size of the structure
3. Two Dimensional Arrays, passing and returning arrays from a fn
4. Different stages of C program compilation
5. how fork() works
6. What are various ways to debug memory corruptions.
7. various IPCs
8. Heap and Stack memory-based Question

4–6 yrs of experience – I would have asked:

1. How memory is allocated by the OS
2. Internal and external fragmentation, what can be done to avoid it
3. System calls, strace()
4. Trade-of of one IPC over other
5. various ways to communicate with kernel and comparison
6. Data (De)Serialization in C
7. RPC in C
8. callbacks advanced application
9. typedef Vs #define
10. Generic programming in C using macros
11. Thread Synchronization
12. Heap and Stack memory-based Question

7+ yrs of experience – I would have asked

1. Have you designed any system module to solve any problem
2. Design thread library 0 what functionalities would you incorporate in and how?
3. What are Dos and Dont’s for writing a robust and flexible library
4. How to write generic code in C
5. Various ways to implement timers in C, and comparison of approaches
6. How do Interrupts work ?
7. IPCs and comparison
8. How would you convert a C code to C++ and vice versa
9. How to write a tool to detect memory leaks Or garbage collection
10. Design your own memory allocation tool. Why would you write your own memory allocation scheme?
11. When to go for Multi-process design over Multi-threaded design and vice versa
12. How ValGrind tool works
13. In production code, would you favor recursive but simple logic, Or Nonrecursive but complex logic, and why?

If you analyze the pattern,

Candidate with 1–3 yrs of experience, I would choose to ask more of a direct and straightforward Questions.

Candidate with 4–6 yrs of experience, I would choose to ask more advanced technical C Question plus some comparison of approaches based Questions

Candidate with 7+ yrs of experience, I would choose to ask more of a design and Analysis based Question.

Note that, since the Question pertains to C and System Programming, so I have not mentioned Data structures and Algorithms.