JacobOS

C and x86 assembly.

Live system loading…

Click the screen, then type. Input goes straight to the kernel's keyboard driver.

Try it

A small shell with real directory traversal, a persistent filesystem, and user programs in ring 3.

helplist every command

lslist the current directory

cat readme.txtprint a file

cd docschange directory

mkdir notesmake a directory

echo hi > f.txtwrite a file

pslist concurrent tasks

spawnstart a background task

gtrun cooperative green threads

exec /hellorun an ELF program in ring 3

meminfoheap & cache stats

stresshammer the allocator & scheduler

Files persist across visits — the whole machine state, disk included, is saved to your browser's IndexedDB when you leave (or press Save session) and restored next time. Reset disk wipes it for a clean boot.

Under the hood

Boot: Custom MBR bootloader → protected mode → C kernel, loaded over LBA disk reads.
Interrupts: IDT with full ISR/IRQ stubs, remapped 8259 PIC, PS/2 keyboard driver.
Memory: Bitmap physical frame allocator, 4 MB-page paging, first-fit kernel heap.
Tasking: 1:1 preemptive kernel threads, round-robin scheduler driven by the PIT.
Storage: ATA PIO driver → hierarchical filesystem → write-back block cache.
Ring 3: ELF loader, TSS privilege switch, int 0x80 syscalls — user programs run unprivileged.