What is BIOS in Computer? | JKSSB Mock Test

BIOS Explained in Simple Terms

BIOS stands for Basic Input/Output System.

It’s a small program stored in a chip on your motherboard that runs before your operating system (Windows, Linux, macOS) ever starts.

Why BIOS Exists

• It initializes and checks hardware components like RAM, CPU, and storage.
• It provides basic instructions that let your OS communicate with peripherals (keyboard, USB, etc.).
• It contains a setup utility for adjusting crucial system settings.

How BIOS Works (Boot Process)

1. Power-On Self-Test (POST)
   BIOS begins by testing hardware—if anything fails, you’ll hear beep codes or see error messages.


2. Boot Loader Activation
   Once hardware checks pass, BIOS looks for the boot drive and starts loading your OS into memory.


3. Handing Control Over
   After loading essential OS components, BIOS passes control to the operating system.


4. CMOS/BIOS Setup Storage
   Settings like date, time, and boot order are stored in CMOS memory backed by a small battery.

Key Functions of BIOS

• POST: Verifies hardware health every time your computer turns on.
• Boot Device Order: Controls which device (e.g. SSD, HDD, USB) loads first.
• BIOS Setup Utility: Lets you adjust CPU, RAM, security, and boot preferences.
• Low-Level Drivers: Offers basic support for keyboard, storage, and other hardware before drivers load.

BIOS vs UEFI

• Legacy BIOS: The classic firmware used since the 1980s; limited to drives under ~2 TB.
• UEFI (Unified Extensible Firmware Interface): Modern firmware with graphical menus, faster booting, and better security.

Most PCs since 2020 use UEFI, but still retain a “compatibility BIOS” mode.

Accessing BIOS or UEFI Settings

• Common Keys: F2, F10, Del, Esc—hit them during the POST screen.
• Windows 10/11: Go to Settings → Recovery → Advanced Startup → UEFI Firmware Settings.
• Linux: Use your system’s reboot-to-firmware command or monitor the startup keys.

BIOS Settings You Can Modify

• Boot sequence (e.g. boot from USB first)
• System clock and date
• CPU features (like virtualization or overclocking)
• Enable/disable devices (audio, LAN, USB ports)
• Security (set supervisor passwords, configure Secure Boot)

Tip: Be cautious—wrong settings might prevent your computer from booting.
Always record original values before changing BIOS settings.

CMOS Battery – The BIOS Power Source

Inside your motherboard lies a coin-cell battery (usually CR2032) that keeps BIOS settings intact when your PC is powered off.

When this battery dies, you might notice:

• Clock resets on boot
• Reversion to default BIOS configuration

Replacing the battery restores system stability and stops CMOS errors.

Common BIOS Troubleshooting Tips

• Beep Codes: Help diagnose hardware issues—multiple short or long beeps usually indicate RAM, GPU, or CPU faults.
• CMOS Checksum Error: Often caused by BIOS corruption or dead battery. Resetting BIOS or flashing firmware can fix this.
• No Boot: Check boot order or enable compatibility mode if the system won’t start.

FAQs – People Also Ask

Q1: What exactly does BIOS do?
It initializes your hardware, checks for issues, and starts the OS from your storage drive.

Q2: How is BIOS different from UEFI?
BIOS is older and simpler. UEFI is newer, faster, and more secure.

Q3: What if I press BIOS key and nothing shows?
Try restarting and pressing keys like Del or F2 repeatedly during startup, or use OS-based firmware access.

Q4: Can BIOS be updated?
Yes. BIOS updates fix bugs or add hardware support. Always follow safe flashing instructions.

Q5: What happens if the CMOS battery dies?
Your system will forget BIOS settings and reset time/date. Replacing the battery solves this.

Final Take – Why BIOS Still Matters in 2025

Even with modern systems using UEFI, BIOS remains the foundation of your PC’s startup process.

Whether you're adjusting boot options, diagnosing hardware issues, or setting security preferences, understanding BIOS gives you more control over your computer.