Skip to main content

Loading the code workspace…

LC

Parse the BIOS Memory Map (E820)

hard11/15

Write to VGA Text Mode Buffer Set Up x86 Page Tables for Virtual Memory

Language

Compiler

2.0s Limit 256MB

Submit and pass all tests to enable saving to GitHub.

Implementation

Simulate parsing a BIOS E820 memory map in C.

Requirements:

Define E820_ENTRY structure with base, length, and type
Create a sample memory map with mixed region types
Implement parse_e820_map() that iterates entries
Print each region with base, length, type name, and size in MB
Calculate total usable RAM (type 1)
Calculate total reserved memory (type 2)
Show which regions are safe for kernel allocation
Implement find_free_region() that returns largest usable block
Handle entries above 4GB (print as high addresses)
Print summary statistics

Test:

Show all memory regions parsed
Show total usable RAM calculated
Show reserved regions identified
Show largest free block found

Why This Matters

The E820 memory map you're parsing here is exactly what GRUB passes to every multiboot-compliant kernel, and it's the only way an OS learns which physical addresses are real RAM versus reserved for the VGA buffer, ACPI tables, or memory-mapped PCI devices. Allocating a page from a region you mistakenly marked usable is how kernels corrupt firmware data structures or write straight into device registers.

Hints

0 / 3 revealed

Sample validation

Sample case for Run. Submit grades this sample plus all hidden tests.

main.c

Workspace 1.0

← Write to VGA Text Mode BufferSet Up x86 Page Tables for Virtual Memory →