How do I even start programming an os for a computer?

Question

Like my problem isnt the coding part ill learn that but like. WHERE do I begin making it? how did they make mac OS? My problem is like idk where to start typing in my code

Answer 1

Assuming you mean the BIOS and lowest levels you need to learn the architecture of the machine and devices first. Then write a bootstrap program to be called wherever that hardware first looks for an instruction. Start by reading the book called CODE by my hero Charles Petzold. It's the best. I keep copies for young students.

Answer 2

You start by reading up a LOT on the functions of an O/S including how to handle device activity, how to manage the memory mapping hardware (a.k.a. memory management or virtual memory system), task scheduling, access coordination (users, privileges, roles, etc.) Then you design something that handles every one of those features.

At some point you purchase language software that produces TRUE code - not emulated or interpretive code. The assembler is always the most efficient option for the code, but for the programmer, some other language like C or Pascal would be better for the higher-level functions that would be tedious as all heck to code in assembler. Doing it by yourself will make it likely that you'll have your O/S ready in several years.

Answer 3

you need to start with a dialect of assembly & an IDE for it, then, start using C in IDE for C & use those asm codes in it....

Answer 4

You are not remotely ready to do that, if where to write code alone confounds you, such basic idea is like drinking water basic to biology.

Mac OS is very complex, your eyes set on something you can't even reach, and Apple computers are inheritantly locked to run Mac OS while others are enabled to run via Bootcamp.

Answer 5

Typically operating systems are written in C or C++ with a small amount being written in Assembly. Large programming projects are almost always written in an IDE (Integrated Development Environment) which include not just text editors but related tools that make the process quicker. One of the most popular IDEs is Microsoft Visual Studio. There is a free version of Microsoft Visual Studio called Visual Studio Community 2017. Developers usually use a program called VMware or Virtual Box to test their development-builds of operating systems. These days, unless you are Terry Davis, you don't make an operating system from scratch but rather make your own based on a pre-existing one. Building an OS based on a pre-existing one is only possible if you have access to the source code so unfortunately you will not be able to make your own version of Windows unless you worked at Microsoft or your own version of MacOS unless you worked at Apple. You would still be able to make your own Linux or BSD OS, however.

Answer 6

The fact that you don't know how to write source code and compile it into an executable means you are nowhere near ready to write an operating system.

Answer 7

From the sounds of your question, you do not have the smarts to accomplish the task!

Answer 8

There are several Open Source OS's you can download the source code for. For example you can download complete Linux kernel source code from www.kernel.org
Do you actually NEED to create another OS from scratch?
Can you use something like Yacto (https://www.yoctoproject.org/) to create a custom Linux distribution, which would work for your project?

The usual way to start learning to code an OS, is to develop a Driver, or Loadable Module, for an existing OS. Then try loading the driver and run it.
Then you can study other parts of the OS, and gradually expand your knowledge.

Answer 9

Have you attempted to go to the library and browse books about creating as OS?

Are you familiar with the BIOS?

It's an acronym for Basic Input/Output System and is non-volatile firmware used to perform hardware initialization during the booting process (power-on startup), and to provide runtime services for operating systems and programs.[1] The BIOS firmware comes pre-installed on a personal computer's system board, and it is the first software to run when powered on.

https://en.wikipedia.org/wiki/BIOS

When the BIOS is finished doing it initial work, it calls INT 19h to start boot processing. Then the BIOS attempts to locate boot loader software held on a storage device designated as a "boot device", such as a hard disk, a floppy disk, CD, or DVD. It loads and executes the first boot software it finds, giving it control of the PC.

So, that's where you want your OS to be.

The BIOS selects candidate boot devices using information collected by POST and configuration information from EEPROM, CMOS RAM or, in the earliest PCs, DIP switches. Following the boot priority sequence in effect, BIOS checks each device in order to see if it is bootable.

The user can control the boot process, to cause one medium to be booted instead of another when two or more bootable media are present, by taking advantage of the boot priority implemented by the BIOS. For example, most computers have a hard disk that is bootable, but usually there is a removable-media drive that has higher boot priority, so the user can cause a removable disk to be booted, simply by inserting it, without removing the hard disk drive or altering its contents to make it unbootable.

In most modern BIOSes, the boot priority order of all potentially bootable devices can be freely configured by the user through the BIOS configuration utility.

Edit:
Generally, code is just text, so, yes, you can just type it into Notepad (or any other text editor) and save the file.

But that's just the start. You need to compile / assemble that code, and then test it. Testing operating system code is trickier than code for an ordinary application. Application code assume there is a working OS, and the OS does things behind the scenes.

So, you have a lot of studying to do before you even think about typing in any code. Or is this a fake question. It seems that no real questions are getting posted anymore.

Answer 10

An OS has many parts, once you understand what those parts are and what they need to do, you can just pick one and start working on it.

The OS is just a program. So it'll be composed of several source files, as well other tools for helping to compile and run it. For instance you'll probably want to use the "make" tool so you can easily compile and deploy parts of your OS as you're developing it.

As for modern MacOS, it's actually based on another OS called FreeBSD, which is a cousin of Linux.