How Kernels Shape Software: From OS Architecture to NeXTSTEP and the Origins of the Web

Lets talk about heart of Operating Systems - Kernels !!!

We use so many software applications daily, which are designed and engineered by software developers, much of the focus on building such software isn't in building flashy functionalities or over the top features. they do include those too but the main and foremost important focus a good software system has is about how it manages application runtime and its experience particularly - Efficiency. 

An efficient software system is the one that manages the hardware very well. To do that, kernels are used. Kernels bridge the gap between the software and hardware. Kernels are the layout of the operating system that manages the requirements from the software system, program wants memory - kernels allocates the memory from the hardware to the particular program; program wants CPU process - kernels assigns the process to the program; program wants to read a file - kernels allows the program to view the file from the system; program wants input and output interaction - kernels assigns I/O operations. All in all, kernel bridges the gap between the software and hardware that too using efficient architecture. 


image courtesy - https://en.wikipedia.org/wiki/Kernel_%28operating_system%29


 Now you may ask - When is a kernel designed ? how is a kernel designed ? 

1] When is a kernel designed ? 

- A kernel is designed at the development stage of designing an operating system, even before the main components of OS like UI, apps, utilities are designed. 

2] How is a kernel designed ? 

Designing a kernel is a system-level engineering process involving planning, coding, and testing.



Image Courtesy - https://www.includehelp.com/operating-systems/types-of-kernels.aspx

A. Architectural Design Phase

1. Choose Kernel Architecture

Decide the structure:

  • Monolithic → All services in kernel

  • Microkernel → Minimal kernel + user space services

  • Hybrid → Balanced

  • Exokernel → Very low-level

  • Nanokernel → Minimal operations

This is the heart of kernel design.

B. Low-Level Hardware Understanding

Developers must understand:

  • CPU modes (User mode, Kernel mode)

  • Interrupts and exceptions

  • Memory paging & segmentation

  • Device memory-mapped registers

  • Boot process

  • System buses

  • Cache management

Because kernel code directly interacts with hardware.

C. Implementation Phase (How Kernel is Written)

1. Implement the Kernel Core

This includes:

  • System Call Interface

  • Interrupt Handlers

  • Exception handlers

  • Scheduler

  • Memory Manager (paging, virtual memory)

  • Device Driver Framework

  • File System Interface

2. Write in Low-Level Languages

Kernels are written using:

  • C language → main kernel code

  • Assembly (ASM) → hardware-specific parts (boot, context switching)

3. Define Data Structures & Algorithms

Kernel requires highly efficient data structures:

  • Process Control Block (PCB)

  • Scheduling queues

  • Page tables

  • File system tree

  • Buffer caches

  • Device descriptor tables

Here comes the Most Interesting part !! 

The systems that you use today are all in their OS design are attributed to NEXT OS which started the onset of using micro- kernels to manage applications and their designs. 



                              Image Courtesy - https://fortune.com/2016/12/20/apple-next-anniversary/

1. Microkernel → Modular, Message-Based System

NeXTSTEP used the Mach microkernel, which kept only essential functions in the kernel and moved everything else to user space.
This created a clean, modular, message-passing architecture.

This idea directly influenced:

  • Object communication in OOP

  • Component-based software design

  • Stable, well-structured applications

2. Microkernel + Objective-C → Powerful Object-Oriented Environment

NeXTSTEP used Objective-C, whose message-sending style matched the microkernel’s message-passing design.

This allowed:

  • True object-oriented frameworks (AppKit, Foundation)

  • MVC architecture

  • Rapid, reusable component development

These became the foundation of macOS, iOS, and modern application frameworks.

3. NeXTSTEP Enabled the Birth of the Web

The first:

  • Web browser, and

  • Web server

were built by Tim Berners-Lee on a NeXT computer running NeXTSTEP because the OS had:

  • Strong OOP frameworks

  • Built-in networking

  • Easy development tools

  • Microkernel stability

This made early web development possible and efficient.

4. Led to Modern Web & App Architecture

NeXTSTEP inspired:

  • WebObjects (one of the first web app frameworks)

  • MVC pattern used in web frameworks today

  • Clean UI design tools (Interface Builder)

  • Component-driven development (influencing React, Rails, Django)


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