Intro to x86 Assembly Language (Part 1)

Introduction to x86 Assembly Language

This section introduces the basics of x86 assembly language, including what it is and how it differs from other programming languages.

What is Assembly Language?

• Assembly language provides almost no abstraction over the native instruction set for the processor.

• It is a human-readable form of machine code that gives more direct control over the processor but requires more code to perform relatively basic tasks.

• Assembly languages are closely tied to the specific CPU architecture that they run on.

Understanding Processors and Registers

• The processor follows a sequence of instructions in order to perform tasks.

• The x86 architecture has several general-purpose registers that you can use to compute with as well as several special-purpose registers.

• The size of the registers is reflected by your CPU architecture as well.

Understanding Stacks and Assemblers

• The stack behaves similar to a last in first out or LIFO data structure, where values can be pushed onto and popped off of it.

• The stack pointer holds the location of the top of the stack, which can be changed and altered.

• An assembler is required to assemble assembly code into machine code.

Installing an Assembler

This section covers how to install an assembler for working with assembly code.

Installing NASM Assembler

• NASM assembler can be installed using apt install command on Ubuntu or similar Debian distributions.

• Other good assemblers are available, but syntax may differ quite a bit between different assemblers.

Writing Your First Assembly Code

This section covers writing your first assembly code using an assembler.

Defining Entry Point for Program

• Define entry point for program using global keyword followed by a colon creating a label.

Moving Values into Registers

• Use move instruction to move values into registers.

Creating Labels and Defining Instructions

• Labels are used to name locations in code.

• Instructions can be defined using mnemonics, which represent machine instructions.

Introduction to Assembly Language Programming

In this section, the instructor introduces assembly language programming and explains how it works.

Basics of Assembly Language Programming

• The value stored in EAX register determines the type of system call made.

• NASM is used to assemble the program into machine code.

• LD command is used to build an executable from the object file.

• Three types of instructions are introduced - MOV, SUB, and INT.

Basic Instructions in Assembly Language Programming

In this section, the instructor explains basic instructions in assembly language programming.

Basic Instructions

• Syntax for assembly instructions includes a mnemonic followed by operands separated by commas.

• Multiplication and division are applied to the EAX register.

Building a Simple Program in Assembly Language Programming

In this section, the instructor demonstrates how to build a simple program using inline data.

Building a Simple Program

• A string of bytes named "msg" is created containing "Hello World" followed by a newline character.

• Length of the string is determined by subtracting location after string from location before string.

• System call is performed that writes our string to standard out using EAX set to 4 as system write call and EBX set to 1 as file descriptor for standard out.

• Another system call is performed to exit the program with an exit status of 0.

Program Control Flow in Assembly Language Programming

In this section, the instructor covers program control flow like conditions and iteration.

Program Control Flow

• No bullet points available as the instructor only mentions that he will cover program control flow in the next video.