Tema 1 - Introducción a la computadora.pdf

Introducción a la computadora

Computadora



La computadora es un dispositivo electrónico con las

características:



Construida por diferentes dispositivos electrónicos.



Contiene dispositivos de almacenamiento para datos y programas.

Provista de unidades de entrada y salida.

Funciones



Procesar Datos



Interpretar y ejecutar comandos de entrada y salida

Realizar cálculos y operaciones lógicas



Almacenar Información



Datos



Programas



Transferir datos

Componentes principales



Unidad Central de Procesamiento (procesador)

 Controla el funcionamiento de la computadora y lleva a cabo sus funciones de procesamiento de datos.



Memoria Principal

 Almacena Datos



Unidades de Entrada y Salida

 Transfiere datos entre la computadora y el entorno externo



Medios de interconexión

01001010

01101010

01101111

Unidad Central de Procesamiento



El CPU consiste de uno o más

chips dispuestos dentro de la

“tarjeta madre” de la

computadora (motherboard)



El CPU controla todos los

dispositivos y lleva a cabo el

procesamiento de los datos, de ahí

que sea el componente más

Fundamentos de Sistemas Operativos



Sistema Operativo



Programa que administra los recursos de la computadora,

proporciona servicios a los usuarios y planifica la ejecución de

los programas.



Objetivos:



Comodidad: Un SO hace que la computadora sea más fácil y

cómoda de usar.



Eficiencia: Un SO permite que los recursos de la computadora

SO como administrador de recursos



El Sistema Operativo se encarga de controlar los

recursos de la computadora que le permiten mover,

almacenar y procesar información, así como controlar

estas funciones.



En otras palabras, el SO es un mecanismo de control

Procesamiento de Información



Los sistemas operativos se pueden clasificar dependiendo

de:



Tipo de Acceso

 Por lotes



Tipo de programación

 Multiprogramación ó multitarea

Tipo de acceso



Interactivo



El usuario interactúa con el hardware



Si existía un error la computadora se detenía y se indicaba la

condición de error (tarjetas perforadas).



Por lotes



El programa se introduce en una cola de lotes.

El lote es un conjunto de programas similares.

Tipo de programación



Monoprogramación



Trabaja en un solo programa.



La memoria se divide en dos partes:

 Programa



Multiprogramación ó multitarea

Varios programas



La memoria correspondiente al programa se divide en varias

Tiempo compartido



Tiempo compartido



Se ejecutan varios trabajos pero no en procesamiento por lote,

Data and Information



Digital Data Representation

Computers use 0 and 1

 Easier to build circuits to discriminate between Two voltages

 On and off



Digital device – discrete numbers (0, 1)

Measures of Bytes

Decade

70s

80s

90s

2000

Capacity

Thousand

_s

Millions

Billions

Trillions

Prefix

Kilo (K)

Mega(M)

Giga (G)

Tera (T)

Moore´s Law



The number of transistors in a silicon chip doubles

every year (18 months).



Microchips

 Circuitry is becoming smaller.  Faster microchips.



Storage

 Disk capacity is increasing.

 Consumer demand faster devices.



Physical limits

System Architecture



RAM (Random Access Memory)



Temporalily holds data.



Usually holds 8 bits (1 byte).

Volatile.



Functions:

 Holds data waiting to be processed or stored.  Holds OS instructions (kernel).



Capacity - Megabytes (MB)

System Architecture ...



Virtual Memory



Computer’s ability to use disk storage to simulate RAM.

Use of space in the HD as an extension of RAM.



Advantages:

 Run large programs that do not fit on RAM

 Run multiple programs.



Disadvantages:

 Not as fast as RAM.

System Architecture ...



ROM (Read-Only Memory)

One or more chips.



Contains instructions to help the computer prepare for tasks

(BIOS)



Types:

 ROM – Read-only

 PROM – Programmable

System Architecture ...



CMOS Memory



Requires very little power.



Can be powered by a battery.

System Architecture ...



CPU (Central Processing Unit)



Circuitry that executes instructions to process data:

1.

Retrieves instructions and data from RAM.

Processes instructions.

Input/Output



Expansion bus



Segment of data bus that transports data between RAM and

peripheral devices.



Expansion Slot



End of the expansion bus.



Allows connection of an Expansion Card.



Expansion Card

Input/Output ...



Expansion Cards ...



ISA (Industry Standard Architecture)

 Modems or slow devices.



PCI (Peripheral Component Interconnect)

 64-bit data bus.



AGP (Accelerated Graphics Port)

Input/Output ...



Expansion port



Connector that passes data in and out of a computer or

peripheral device.

Storage Devices



Bits and Bytes



Bit – smallest unit (0 and 1)

Byte – 8 bits.



Nibble – 4 bits.



Storage Medium



Contains data (HD, CD-ROM, floppy, DVD, USB, etc.)



Storage Device

File Allocation Table



Called FAT.



Cluster – group of sectors.



FAT (map of the disk)

Entry per cluster on disk.



Number on next cluster (forms a chain)

Last cluster contains a special mark.



Fragmentation

Disk, Tapes, CDs, etc.



Criteria to compare storage devices:



Versatility

 Number of media that can be read/write.



Durability



Capacity

Speed

 Access time – time to locate data and read it.

 Random and sequential access.

Proceso de Arranque de una

Computadora

Proceso de arranque



Secuencia de eventos que ocurre desde que se enciende

la computadora hasta que esta lista para aceptar

comandos.

Pasos del proceso de arranque

Pasa corriente a la tarjeta madre

2. Ejecutar programa de arranque

Almacenado en ROM (Boot program)

3. POST (Power-On Self-Test)

Realizar diagnosticos de componentes cruciales.

4. Cargar el Sistema Operativo

Copiado de disco a RAM

5. Verificar configuración y preferencias

Cargar ambiente definido por el usuario

POST

1. Verificar tarjeta de gráficos  Despliega información BIOS

2. Verificar RAM

 Despliega información RAM

3. Verificar teclado

4. Verificar dispositivos de E/S

5. Verificar discos presentes

Cargar SO

 Master Boot Record (MBR)  Primer sector del primer track.  Encargado de cargar el SO

 Secuencia de búsqueda:  A -> encontrado -> default  C -> default

 Búsqueda de archivos:  Io.sys

 Msdos.sys

BIOS (Basic Input/Output System)



SW más primitivo.



Maneja señales que controlan HW.



Tres funciones principales:



Inicialización del HW (encendido.)

Cargar el SO.

BIOS ...



Siempre presente.



En ROM



Se copia a RAM durante el arranque.

Data Integrity



Computer failure = loss of data



Type of data:



Lost data (missing data) = inaccesible data

Stolen data



Inaccurate data



Operator error



Lost data

Data Integrity ...



Power Failures, Spikes and Surges

Power failure = complete loss of power



Power spike = increase in power (less than one-millionth of a

second)

Data Integrity ...



Power Failures, Spikes and Surges ...

Prevention

 Unplug during electrical storms.

 UPS - Contains a battery and circuitry  Surge strip

 Power strip – does not filter spikes and surges

Data Integrity ...



Data Backup



Backup Equipment

 Floppy disk, Zip disk, Removable HD, CD-RW, DVD-RAM, Tape, Paper

(printed).

 Considerations:

 Must hold all your critical data.

 Speed

Data Integrity ...



Data Backup ...



Backup SW

 Copy utility

 Disk copy program

 Backup SW

 HD backup to tapes and disks.

 Select files

Data Integrity ...



Data Backup ...

Types of Backups

 Full backup

 Copy of all files = safe.

 Takes long time.

 Computer cannot be used during backup.

 Easy to recover from backup.

 Differential backup

 Full backup + files changed

 Copies files changed since last full backup.

 Takes less time than full backup.

Data Integrity ...



Data Backup ...



Types of Backups ...

 Full backup + changes from last backup (any)

 Full backup

 Changes from full backup

 Changes from last backup

 Fastest backup method

Risk Management



Security techniques



Establish policies and procedures



Restrict physical access to computer systems



Restrict online access to data



User rights

 Create

 Write

 Read

Risk Management ...



Security techniques ...

Encrypt data

 Encryption – decryption process

 Needs a key

 Private key encryption

 Both sender and receiver have a private key.

 Only they can encrypt and decrypt messages.

 Public key encryption (PKE)

 Pair of digital keys.

 Public key – for everyone (encrypts)

Risk Management ...



Internet security

Problems

 Java applet

 Processing and interactive capabilities

 Sandbox – prevents applets from running amok and damaging files

 ActiveX controls

 Downloaded directly to the computer.

 Have no sandbox

Risk Management ...



Secure E-commerce



https:

 Uses security protocol SSL.

 Establishes a secure connection.



S-HTTP

 Encrypts data one message at a time.



Cookie

Risk Management ...



Computer virus



Definition:

 Program that attaches itself to a file,  Reproduces itself, and

 Spreads to other files.



Payload – ultimate mission of a virus



Types:

 File virus – attaches itself to an application program  Boot sector virus – in boot sector

Risk Management ...



Trojan horse



Program that appears to perform one function while doing

another.



Not a virus

 Does not replicate itself.

Risk Management ...



Time bombs and Logic bombs



Time bomb

 Triggered by an event.

 Carried by viruses or trojan horses.



Logic bomb

Risk Management ...



Worms



Description:

 Program designed to enter a computer system through security holes.

 Reproduces itself.

 Does not need to be attached to a document of application.