Part 7 - Word Lengths

For a complete table of contents of all the lessons please click below as it will give you a brief of each lesson in addition to the topics it will cover. https://github.com/mytechnotalent/Reverse-Engineering-Tutorial

Before we dive into the architecture lets talk about how we define various bits and how they are structured within the processor.

In both x64 and x86, we define a byte as 8 bits. We define a word as 16 bits. We define a double word as 32 bits and a quadword as 64 bits. Finally we define a double quadword as 128 bits. 

Intel processors store bytes as what we refer to as "little endian," meaning lower significant bytes are stored in lower memory addresses. Lets give an example of a simple 16-bit or 2 byte value. On disk - 0xAABB. When it goes into memory it is stored as 0xBBAA as I hope this provides a good visual as this concept can be quite confusing.

Keep in mind, 8 bits make up a byte. 4 bits are also called a nibble which are equivalent to one hex digit.

Next week we will dive into general architecture! Stay tuned!