KernelPath vs Opcodes

KernelPath is a comprehensive, interactive course on operating system kernels — built entirely for iPad and iPhone. GO FROM ZERO TO KERNEL FLUENT Work through 7 structured modules covering the full Linux kernel stack: architecture, processes, memory, file systems, networking, security, and device drivers. Each lesson combines clear explanations with real C code examples, diagrams, and practical command-line usage. LEARN BY DOING 14 interactive labs let you visualize concepts that textbooks struggle to explain: - Step through the boot sequence from BIOS to login - Watch the CFS scheduler assign CPU time to competing processes - Walk a page table translation from virtual to physical address - Trace a system call from user space into the kernel - Animate a TCP three-way handshake in real time - Build and test seccomp filters on system calls - Follow a read() call from application through the driver stack to hardware PRACTICE IN A REAL TERMINAL A built-in Linux terminal simulator gives you a virtual machine to explore. Navigate a realistic filesystem with /proc, /sys, /dev, and /etc. Run 50+ real commands — ls, ps aux, free -h, ip addr, cat /proc/cpuinfo, lsmod, and many more — all producing authentic Linux output. TEST YOUR KNOWLEDGE Each module ends with a quiz. Detailed explanations for every answer reinforce what you learned and fill in gaps. TRACK YOUR PROGRESS A personal dashboard shows completed lessons, quiz scores, and module-by-module progress so you always know where you left off. WHAT YOU'LL LEARN - Kernel architectures: monolithic, microkernel, and hybrid designs - Process lifecycle: fork(), exec(), scheduling, IPC, and signals - Virtual memory: page tables, the MMU, allocation, and swap - File systems: VFS, ext4 internals, inodes, and permissions - Networking: TCP/IP stack, packet encapsulation, sockets, and netfilter - Security: DAC, capabilities, SELinux, AppArmor, and seccomp - Device drivers: character and block devices, udev, and driver architecture BUILT FOR LEARNERS No prior kernel experience required. Start from "What is a Kernel?" and build up to writing device drivers and configuring seccomp filters. Perfect for computer science students, self-taught developers, SREs, and anyone who wants to understand what happens beneath the surface of every application.

Opcodes – The Retro CPU Reference The definitive opcode reference for the legendary processors that launched the personal computer revolution. Whether you're a retrocomputing enthusiast, a student of computer history, writing code for classic hardware, or just a big old nerd - the Opcodes app gives you everything you need. Eighteen iconic processors covered: Intel 4004 · Intel 8008 · Intel 8080 · Intel 8085 · Intel 8088 · Zilog Z80 · Motorola 6800 · Intel 8085 · Motorola 6809 · MOS 6502 · Signetics 2650 · RCA 1802 - SC/MP · Motorola 68000 · Intel 8086 · WDC 65816 · Texas Instruments TMS9900 · INMOS Transputer · ARM2 For every opcode:  • Full description of what the instruction does. • Hex, octal, and decimal values. • Flags affected. • Addressing modes and cycle counts. • Assembly code examples - including loops, conditionals, and common patterns. More than just opcodes:  • CPU history and historical context. • IC pinout diagrams. • Notable systems that used each CPU, with memory maps and other background information. • Chip variants and successors. • A silly card game(!) • Simple assembler / disassembler for many CPUs. Built for exploration:  • Search for opcodes by name or category. • Sort by mnemonic, opcode byte, or category. • Filter by category, Quick Find with a colorful map. • Undocumented instructions clearly marked and optionally displayed. More than microprocessors:  • Information on key support chips: video, sound, memory and more. Cool design:  • Clean, readable layout optimised for quick reference. • Multiple colour themes. • Full "dark mode" support. Everything is included with absolutely no in-app purchase required. Recent additions: • Quiz game - test your CPU knowledge! • Share CPU cards - beautiful shareable images showing specs and history for any processor • External references - curated links to community resources for all 18 CPUs • "Opcodes display first" setting - choose whether selecting a CPU shows opcodes or info first • Chip-maker colour themes - Zilog, MOS Tech, and Motorola replace the old themes • Enhanced 6502 docs - JMP page boundary bug, BRK behaviour, and Read-Modify-Write quirks • Fixed Scratchpad hang when switching tabs