Table 1. Software Hierarchy Levels

PROGRAMACION
PROGRAMACION DE SISTEMAS

Level

Description

Application Program
High-Level Language
(HLL)

Chapter 1
What
What is Assembly Language?
Data
Data Representation

Programs are compiled into either assembly language or machine language.
E.g. C++, Pascal, Java, Visual Basic, etc.

Operating Systems

Introduction

Software designed for a particular class of applications Contains procedures than can be called from programs written in either high-level language or assembly language. This system may also contain an application programming interface (API).

Assembly Language (ASM) Uses instruction mnemonics that have a one-to-one correspondence with machine …ver más…

Formal structures
No formal structure. make it easy to organize and maintain.

Hardware device driver. Awkward
Awkward coding techniques required.

Hardware
Hardware access is straightforward and simple. Business application for multiple platforms.

Portable.

Difficult to maintain.

Embedded systems and computer games requiring direct hardware access.

Produces too much executable code, and may not run efficiently.

Ideal, because the executable code is small and runs quickly.

6

Machine Language

Binary Numbers/Storage Size

An assembler is a program that converts
ASM code into machine language code: mov al,5 (Assembly Language)
1011000000000101 (Machine Language)

are are used to store both code and data
On Intel’s x86:

most significant byte is the opcode for “move into register AL” the least significant byte is for the operand “5”

byte = 8 bits (smallest addressable unit) word = 2 bytes doubleword = 2 words quadword = 2 doublewords

Directly programming in machine language offers no advantage (over Assembly)...

7

8

Data
Data