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What is Proyecto1cc7?

Proyecto1cc7 is an educational bare-metal operating system written in C and ARM assembly, designed to run directly on ARM Cortex-A8 hardware (BeagleBone Black) and in QEMU emulation (versatilepb machine). It implements the core primitives of a real-time OS from scratch — no Linux, no RTOS, no libc. The OS demonstrates:
  • Preemptive multitasking — a hardware timer fires IRQs that trigger context switches between processes
  • Round-robin scheduling — a circular queue ensures each process gets CPU time fairly
  • Full register save/restore — all ARM banked registers (SP, LR, SPSR) are saved and restored correctly on every context switch
  • Dual-platform support — the same codebase targets both real BeagleBone Black hardware and QEMU, selected at compile time via TARGET
  • Minimal standard library — PRINT/READ, string utilities, and numeric conversion run without any OS or libc dependency

Quickstart

Build and run the OS in QEMU in under five minutes

Architecture overview

Understand how the OS components fit together

OS internals

Deep dive into process management and scheduling

Platform support

Configure for BeagleBone Black or QEMU

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Project structure

Proyecto1cc7/
├── OS/           # Kernel: scheduler, process, UART, timer, watchdog
│   ├── root.s    # ARM assembly: vector table, IRQ handler, yield, boot
│   ├── os.c      # main(), schedule(), process init
│   ├── process.c # Process struct and initialization
│   ├── scheduler.c # Round-robin queue operations
│   ├── uart.c    # UART0 serial I/O (platform-abstracted)
│   └── watchdog.c # BeagleBone watchdog disable
├── Lib/          # Minimal standard library
│   ├── stdio.c   # PRINT() / READ() — printf-like over UART
│   ├── string.c  # my_strncpy — bounded string copy
│   ├── alphanumeric.c # itoa, ftoa, atoi, atof
│   ├── rand.c    # rand_custom() / srand_custom() — LCG PRNG
│   └── timer.c   # Timer driver (BeagleBone DMTIMER2 / QEMU SP804)
├── User/         # User-space processes
│   ├── P1/main.c # Process 1: prints a counter
│   └── P2/main.c # Process 2: prints letters a–z
├── linker/       # Platform linker scripts
│   ├── linker_beagle.ld
│   └── linker_qemu.ld
└── Makefile      # Build system (TARGET=beagle|qemu)

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Key concepts

ConceptImplementation
Process control blockProcess struct in OS/process.h
Ready queueCircular linked list in OS/scheduler.c
Context switchARM assembly in OS/root.s (irq_handler, yield)
Timer interruptBeagleBone DMTIMER2 or QEMU SP804 in Lib/timer.c
Serial outputUART0 with platform register abstraction in OS/uart.c
Memory layoutLinker scripts assigning separate RAM regions per process

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