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In this section, we will talk about file system and write a simple module to parse the structure of file system

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.

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In the end, we will see how to run the programs in the console with the help of the file system.

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The file system we will use in the system is fat16. 

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You may use the file system in the operating systems like DOS or windows 95. 

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The reason we choose fat16 file system is that it’s easy to understand 

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and implementing read operation is simple as well. 

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Also, the operating system we use nowadays such as windows, linux and macos can recognize fat16 system 

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and read and write data into the system, which makes the interaction with it more easily. 

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For example, we build a program and drag and drop it to the fat16 image, 

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then we can boot the image, find the program and run the program in our system

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.

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If we want to read a text from the file, we can achieve it by defining a string 

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with the characters we want in the assembly code and assemble it to the binary file.  Copy the file to the image 

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and read the data from the file.

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The data we read from the file will be the characters we want.

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In the following lectures, we will go into details about these operations. The main goal of this section is 

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to show you the process of parsing the file system structure and write a file module to add open, read operations 

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so that the user programs can access the file system. We will also focus on 

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how to combine the process module with file system to run the programs in the file image. 

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Therefore, I will add some restrictions on the file module in our system to simplify the building process 

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and direct your attention on the main goal of the section. 

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Before we build the file module, there is one problem, that is, where our files are stored 

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and how to access them. 

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Normally, the files are stored in the disk. The operating system reads and writes files data into the disk. 

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Unlike the data in the main memory, 

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the data in the disk stays unchanged after we shut down the computer. 

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But accessing the disk requires us to write a disk driver, which is not an easy task to do. 

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So writing a driver is not an option for the moment. 

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Instead, we will load all the data from disk into memory when we are in the boot process. 

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Remember when we are in the real mode, we load the loader file and kernel file using bios service, 

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and now we read the disk into memory using the same method, which means the entire file system is in the memory when our system runs.

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Since we haven’t created a fat16 image, we will see how to create one

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and inspect the fat16 image in the next video. 

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So let's get started.