Sunday, 25 July 2021


What is Computer?

A Computer is an electronic device that stores, retrieves and process data or which manipulates data according to a list of instructions and which is composed of hardware and software. Therefore it used for surfing, typing, programming, playing games, etc,. It is a hardware machine and storing of data and displaying information with the help of programmable language using operating systems software. However it uses a windows operating system software to provide a graphical user interface. After that the windows Operating systems which uses windows 7, windows 8 and windows 10. In other words operating system is interface between the user and hardware.

A computer is a sequence of logical operations through a programming languages. A control unit systems used as a industries and other devices like mobile phones such as smart phones. A central processing unit is used to performs a logical operations and the peripheral devices are used such as input devices and output devices. The Input devices are keyboard, mouse, joystick, scanners, etc,. and the output devices are monitor, printer, speakers, etc,. A general purpose devices used like personal computers and mobile devices.

Elaboration (or) Full Form Of Computer

C  - Common
O  - Operating 
M  - Machine 
P   - Particularly 
U  - Used   (for) 
T  - Technical 
E  - Education   (and) 
R  - Research


What is CMOS?

CMOS stands for Complimentary Metal Oxide Semi-Conductor and it stores roughly 64Kb of data. It is the part of the southbridge in most computers. The specification stored in Complimentary Metal Oxide Semi-Conductor must match hardware and it allows you to access the BIOS. When hardware is change or update, Complimentary Metal Oxide Semi-Conductor must be updated.

CMOS Battery

Accessing BIOS through CMOS setup

Complimentary Metal Oxide Semi-Conductor can only be accessed when the PC is booting and key combination at start-up. The changes are stores on an NVRAM Complimentary Metal Oxide Semi-Conductor chip. The mouse doesn’t work in Complimentary Metal Oxide Semi-Conductor setup.
  • AMI and AWARD BIOS – DEL key 
  • PHOENIX BIOS – CTRL, ALT and ESC keys or F2     


Complimentary Metal Oxide Semi-Conductor is stored in an SRAM chip called Non-Volatile Random Access Memory (NVRAM). It stores data that is uses by the BIOS and NVRAM is powered by Complimentary Metal Oxide Semi-Conductor battery. The modern BIOS is stores in EEPROM and EPROM and SRAM means motherboards are updateable. In older motherboards, you can also reset Complimentary Metal Oxide Semi-Conductor. 

Other CMOS Settings

  • Load High Performance defaults 
  • Load BIOS setup defaults 
  • Supervisor password 
  • User password 
  • Disconnect the battery for 1 hour to erase the password! 
  • Complimentary Metal Oxide Semi-Conductor can also be clear using a jumper 

Clear CMOS Jumper

CMOS Jumper 

These jumpers are often located near the BIOS chip itself or next to the CMOS battery. To clear CMOS, move the small plastic jumper from the 2 pins it's on over to the other pins or remove the jumper entirely if this is a 2-pin setup. In a 3-pin setup where the center pin is share. Any confusion here can be clear up by checking the CMOS clearing steps outlined in your computer or motherboard manual.

To confirm, switch on the computer and check through that the BIOS settings have reset, or the system password is now clear or not. If everything is good, shutdown your computer, return the jumper to its original position, and then power on the computer back. If you don't return the jumper to its original position, then CMOS will clear on every restart of your computer.

Caution: Clearing the Complimentary Metal Oxide Semi-Conductor on your motherboard will reset your BIOS settings to their factory defaults.

CD-ROM Drive Components

CD-ROM Drive Components

A CD-ROM Drive is the commonly used optical storage devices compact disks drive and the components contains a equipment from front view, back view, top view and bottom view portions. The Compact Disk Read Only Memory it contains data were computers can read but not write or erase in CD-ROM it is a type of read-only memory. In the 1990's CD-ROM was use for software and data distribution for the computer. Some CDs are use to play audio on the CD players. Therefore a disk is made up of 1.2 mm thick polycarbonate plastic with a thin layer of aluminum to make a reflective surface. The common size of CD-ROM is 120 mm in diameter and the smaller Mini CD standard size is 80 mm in diameter. The following CD-ROM Drive Components are given below.

  • Optical "Head" Assembly 
  • Spindle Motor, Constant Linear Velocity (CLV) and Constant Angular Velocity (CAV) 
  • Connectors and Jumpers 
  • Logic Board 
  • Audio Output and Controls

Front View

  • Headphone Jack 
  • Manual Eject 
  • Tray Eject Button

Back View

  • Digital Audio 
  • Analog Audio 
  • Jumpers 
  • ATAPI / IDE Connector 
  • Power Connector

Top View

  • Clamper 
  • Pickup 
  • Sled Drive Screw 
  • Motor 
  • Optical Deck

Bottom View

  • Rail 
  • Pickup 
  • Sled Drive Screw 
  • Tray Motor 
  • Spindle Motor 

Saturday, 17 July 2021

BIOS - Basic Input Output System

What is BIOS? 

A BIOS stands for “Basic Input Output System”, is a chip on the motherboard. It is stored in the computers and it is a ROM (Read Only Memory) chip and EPROM (Electronically Erasable Programmable Read-Only Memory) is also known as firmware. It will support all hardware on a 286 AT PC and drivers are required for all other hardware. The original version is 8088 BIOS.


Functions of BIOS 

It stores a set of instructions to tell the PC how to control devices and provides low-level hardware access. It tests hardware on startup using POST and runs “bootstrap loader” after POST. After this, the operating system takes over. The BIOS sit between the hardware and the operating system

BIOS Location

Four Stage Model of Computing

Model of Computing 

Startup Routine

  1. POST 
  2. Bootstrap Loader 
  3. Master Boot Record
  • IO.SYS 
  • NTLDR 

1. During the POST, the BIOS tells drivers to “test themselves” and report back. The problems are flagged either by beeps codes or by messages on the screen. 

e.g. 301- Keyboard failure 

2. Bootstrap Loader 

3. Master Boot Record 

After this the operating system takes over. 


It only checks devices listed in Basic Input Output System. “Devices go forth and test yourselves”. 

  • Beep Codes 
  • Text Errors 
  • Missing NTDLR 
  • Keyboard error or no keyboard present 
  • POST cards POST Error Codes 

Error Code  -  Device 

 100 Series Error (any error in the range 100-199) - Motherboard 

 200 Series Error (any error in the range 200-299) - RAM 

 300 Series Error (any error in the range 300-399) - Keyboard 

 400 Series Error (any error in the range 400-499) - Monochrome Video 

 500 Series Error (any error in the range 500-599) - Colour Video 

 600 Series Error (any error in the range 600-699) - Floppy Drive 

 1700 Series Error (any error in the range 1700-1799) - Hard Drive 

Boot Process

  • CPU’s power good wire “wakes up” the CPU 
  • CPU reads first line of POST program 
  • Bootstrap loader runs 
  • Check if disk is in FDD drive 
  • Look for O.S. on boot sector of hard drive N
  • TLDR or IO.SYS is loaded into RAM 
  • Control is transferred from bootstrap loader to the O.S. 
  • Core O.S. files, drivers and services are loaded into RAM 

BIOS Types

The following Basic Input Output System types are 

  • Motherboard chipsets 
  • Each BIOS designed for a specific chipset 
  • 2Mb of storage 
  • 8088 PC – 384K 
  • Backward compatability 
  • BIOS Manufacturers 
  • AMI 
  • Award 
  • Phoenix 

Updating the BIOS 

  • Original BIOS chips couldn’t be updated that is EEPROM or Flash ROM. 
  • Updates downloaded from Internet 

Why update? 

  • Support for new hardware 
  • Overcome a BIOS bug 
  • “Flashing” the BIOS 

Device Drivers - It is installation disk which loaded into ram on startup. 

Config.sys - Config.sys told the OS where the device drivers were stored. It was located on your hard drive and it is used with the windows operating system and it was originally used with DOS. It is also known as SYSEDIT. 

System.ini - It allowed backward compatibility for older device drivers. It was originally use with windows operating system. 

Registry - In windows, config.sys and system.ini were consolidated in the registry. The registry holds all the configuration settings. It can be accessed through the control panel or device manager and you can also manage directly through regedit and regedit32.