LITTLE ENDIAN SYSTEM MEMORY + ADDRESSING MODES

by JIDE73 4 months ago

GNU/Linux • xterm • zsh 113 views

Endianness y Modos de Direccionamiento (ARM64)

Este programa en ensamblador para AArch64 (ARM64) muestra cómo los sistemas pueden organizar los bytes de un dato y cómo el procesador accede a la memoria de distintas formas.

Little Endian vs Big Endian

Little Endian: el byte menos significativo se guarda primero en memoria. Ejemplo: el número 0x11223344 se almacena como 44 33 22 11.
Big Endian: el byte más significativo se guarda primero. Ejemplo: el mismo número se almacena como 11 22 33 44.

En la práctica, los sistemas ARM modernos usan little endian por eficiencia y compatibilidad.

Addressing Modes (Modos de Direccionamiento)

Son las formas en que el procesador accede a la memoria:

Inmediato: base + un número fijo ([x0, #4])
Por registro: base + valor de otro registro ([x0, x1])
Pre-indexado: incrementa la base antes de leer ([x0, #1]!)
Post-indexado: lee y luego incrementa ([x0], #1)
Relativo al PC: dirección calculada respecto al contador de programa (útil para constantes o texto).

Ejecución en AWS EC2

Compilar y ejecutar:

gcc -o endian_demo aarch64_endian_addressing.S
./endian_demo

El programa imprime los conceptos en pantalla usando llamadas al sistema (write y exit), demostrando cómo se representan los datos en memoria y cómo se accede a ellos.

Leonardo Sebastián Jiménez Delgado
Instituto Tecnológico de Tijuana

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