What is CMOS and How Does it Works?

Clear Cmos
Clear Cmos

CMOS (short for complementary metal-oxide-semiconductor) is usually used to explain the small amount of memory on a system motherboard that stores the BIOS settings. Some of these BIOS settings involve the system time and date as well as hardware settings.

A short for complementary metal-oxide-semiconductor sensor is different—digital cameras use it to convert images into digital data. now let’s discuss CMOS & its Principles.


Other Names for CMOS 

CMOS (pronounced see-moss) is sometimes pointed to as Real-Time Clock (RTC), short for complementary metal-oxide-semiconductor RAM, Non-Volatile RAM (NVRAM), Non-Volatile BIOS memory, or complementary-symmetry metal-oxide-semiconductor (COS-MOS).

CMOS is also an abbreviation for other terms unrelated to what’s discussed on this page, like cellular management operation system and comparison mean opinion score.

Clearing CMOS

Most talk of short for complementary metal-oxide-semiconductor involves clearing C-MOS, which means resetting the BIOS settings to their default levels. This is a straightforward task that’s a significant troubleshooting step for many types of computer problems.

For instance, maybe your system is freezing up during the POST, in which case clearing the short for complementary metal-oxide-semiconductor to reset the BIOS settings to factory default levels might be the easiest solution.

Or maybe you need to clear short for complementary metal-oxide-semiconductor to reset misconfigured BIOS settings to fix specific hardware-related error messages, such as Code 29 errors. Other short for complementary metal-oxide-semiconductor issues revolve around low battery voltage, C-MOS checksum, battery failure, and read error.


How BIOS and CMOS Work Together

The BIOS is a computer chip on the motherboard like C-MOS, without that its purpose is to interact between the processor and other hardware components like the hard drive, USB ports, sound card, video card, and more. A system without a BIOS wouldn’t understand how these pieces of the computer work together.

The BIOS firmware is also what makes the Power On Self-Test to test those pieces of hardware and what ultimately runs the boot loader to launch the operating system.

What Is the BIOS? 

CMOS is also a computer chip on the motherboard, or more specifically, a RAM chip, which means it would usually lose the settings it’s storing when the computer is shut down (just like how RAM contents aren’t maintained each time you restart your computer). However, the CMOS battery is utilized to provide constant power to the chip.

When the computer first boots up, BIOS pulls details from the CMOS chip to understand the hardware settings, time, and anything else stored in it. The chip typically saves as little as 256 bytes of information.

What Is a CMOS Battery?

The CMOS is normally powered by a coin-sized CR2032 cell battery, referred to as the CMOS battery.

Most CMOS batteries will last the lifetime of a motherboard, up to 10 years in most cases. But will sometimes require to be replaced depending on how the device is being used.

Wrong or slow system date and time, and loss of BIOS settings, are significant signs of a dead or dying CMOS battery. Replacing them is as simple as swapping out the dead one for a new one.

More about CMOS & CMOS Batteries

While most motherboards have a spot for a C-MOS battery. Some smaller systems, like many tablets and laptops, have a short external compartment for the C-MOS battery that connects to the motherboard via two small wires.

Some devices that use short for complementary metal-oxide-semiconductor involve microprocessors, microcontrollers, and static RAM (SRAM).

It’s important to understand that CMOS and BIOS are not interchangeable words for the same thing. While they work together for a particular function within the computer, they are two entirely different components.

When the computer is first starting up, there’s an option to boot into BIOS or CMOS. Opening the short for complementary metal-oxide-semiconductor setup is how you can change the settings it’s storing, like the date and time and how the various computer components are first started up. You can also utilize a C-MOS setup to disable/enable some hardware devices.

CMOS chips are good for battery-powered devices like laptops because they use less power than other types of chips. Although they utilize both negative polarity circuits and positive polarity circuits (NMOS and PMOS), only one circuit type is powered on at a time.

The Mac equivalent to short for complementary metal-oxide-semiconductor is PRAM, which is for Parameter RAM. You can also reset your Mac’s PRAM.

CMOS Characteristics

The most important characteristics of short for complementary metal-oxide-semiconductor are low static power utilization, tremendous noise immunity. When the single transistor from the pair of MOSFET transistors is switched OFF, the series combination uses significant power throughout switching among the two stated like ON & OFF.

As a result, these devices do not generate waste heat compared with other types of logic circuits such as TTL or NMOS logic. Which usually use some standing current even if they don’t change their state.

These Cmos characteristics will enable for integrating logic functions with high density on an integrated circuit. Because of this, Cmos has become the most frequently utilized technology to be executed within VLSI chips.

The phrase MOS refers to the MOSFET’s physical structure. Which includes an electrode with a metal gate located on the top of an oxide insulator of semiconductor material.

A material like Aluminum is utilized only once; however, the material is now polysilicon. The designing of other metal gates can be done using a comeback through the arrival of high-κ dielectric materials within the short for complementary metal-oxide-semiconductor process.

The Benefits of CMOS

The significant advantages of C-MOS over TTL are fine noise margin and less power utilization. Because of the no straight conducting lane from VDD to GND, drop times based on the circumstances of input, the broadcast of the digital signal will become low-cost and straightforward through the C-MOS chips.

Short for complementary metal-oxide-semiconductor is used for explaining the amount of memory on the motherboard of the system that will hoard in the settings of BIOS. These settings primarily include the time, date & settings of hardware. Moreover, TTL is a digital logic circuit where bipolar transistors work on DC pulses. Various transistor logic gates are usually made up of a single IC. Now let’s discuss some outputs if the C-MOS drive is active in both ways.

  • It utilizes a single power supply such as +VDD.
  • These gates are pretty simple & input electrical impedance is high.
  • C-MOS logic utilizes less power at any time when it is held in a set state.
  • Power dissipated is insignificant.
  • The temperature is stable, and the fan is far above the ground.
  • Noise resistance is of high quality & so much more.

CMOS Disadvantages

The biggest disadvantage is that its cost will be increased once the processing method increases. Although it can be solved. Moreover, the packing density of the short for complementary metal-oxide-semiconductor is low compared to NMOS.

The problem can be resolved by including protective circuits or other devices. Hence, its chips should be protected from receiving static charges by placing the leads that will destroy the chip. In addition, the other con of the short for complementary metal-oxide-semiconductor inverter is that it uses two transistors as opposed to one NMOS to make an inverter, which means the short for complementary metal-oxide-semiconductor. It utilizes more space over the chip as compared with the NMOS. As a result of the advancement of short for complementary metal-oxide-semiconductor technology, all of these disadvantages have become minor.


[wps_faq style=”classic” question=”Q: How do short for complementary metal-oxide-semiconductor works?”]A: short for complementary metal-oxide-semiconductor Working Principle. In short for complementary metal-oxide-semiconductor technology, both N-type and P-type transistors are used to design logic functions. As a result, C-MOS offers relatively high speed, low power dissipation, high noise margins in both states. And will operate over a wide range of source and input voltages (provided the source voltage is fixed).[/wps_faq][wps_faq style=”classic” question=”Q: What is the difference between BIOS and CMOS?”]A: The BIOS is the program that begins a computer up, and the CMOS is where the BIOS stores the date, time, and system configuration details it needs to start the computer. C-MOS is a type of memory technology. But most people use the term to refer to the chip that stores variable data for the start-up.[/wps_faq][wps_faq style=”classic” question=”Q: How long does a C-MOS battery last?”]A: The C-MOS battery gets charged whenever your laptop is plugged in. It’s only when your computer is unplugged that the battery loses charge. Most batteries will last 2 to 10 years from the date they’re manufactured.[/wps_faq]


A CMOS sensor is diverse digital cameras use it to transfer images into digital data. The essential characteristics of short for complementary metal-oxide-semiconductor is low static power consumption and superb noise immunity. In addition, these devices do not generate waste heat compared with other logic circuits. Hence, we have made everything clear to you related to CMOS. If you still have any queries, feel free to comment to us.