1. CMOS is a type of integrated circuit that stores BIOS settings, while BIOS is a type of software. 2. CMOS is constantly powered to retain information even when the system is off, while BIOS only runs for a short period during startup. 3. Losing CMOS data is not disastrous and can be restored easily, whereas the BIOS is critical for system boot up.

1. CMOS vs. BIOS
BIOS (Basic Input Output System) and CMOS (Complementary Metal Oxide
Semiconductor) are two terms that are used interchangeably in relation
to computer technology. This is because they are very closely related to each
other. In actuality, these two are nothing alike. BIOS is a type of software that
manages the computer hardware when a computer boots-up. It is more like a
primitive operating system that initializes all the resources needed by the true
operating system. On the other hand, CMOS is a type of integrated circuit. The
reason why the two seem so intertwined is the usage of a CMOS chip to store
the information needed by the BIOS. These are the settings you change by
accessing a menu during boot-up; commonly by pressing F2.
One of the main reasons why CMOS was chosen is because of its very low
energy consumption. The CMOS chip is constantly powered and when the system
is off, a CR-2032 battery takes over the job to keep the information stored within.
Once power is lost, the settings are also lost. On the other hand, the BIOS
doesn’t need to be constantly powered as the code is stored in non-volatile
memory. It also runs for only a short period of time before handing control over
to the true operating system.

2. Another difference between CMOS and BIOS is their importance. While the
contents of CMOS are important, losing it is not really disastrous for the entire
system. It can easily be restored by going to the menu during boot-up. The BIOS
code is very important as without it, the computer would not be able to boot. To
repair, the chip containing the BIOS needs to be removed and reprogrammed.
There are many safeguards to prevent the corruption of the BIOS; including
multiple restrictions to prevent accidental corruption and employing multiple
chips containing the same BIOS for disaster recovery.
The term CMOS has stuck even though CMOS is no longer employed for
quite some time. Flash memory has become the medium of choice for storage. On
the other hand, the BIOS is still in wide use in many modern computers; although,
BIOS is expected to be replaced with UEFI in the near future.
Summary:
1. CMOS is type of chip while BIOS is a simple operating system
2. CMOS should always bepowered but not the BIOS
3. CMOS is not critical while BIOS is
4. CMOS is no longer in use while BIOS still is

3. CMOS is Complementary Metal Oxide Semiconductor. Because of its characteristics
of the read and write, CMOS is used to save data about computer parameters set in
BIOS program on motherboard. So its main function is save data.
Two: Main Function Difference between BIOS and CMOS
CMOS main function:
1. Quick Power on Self - Test
When computer is starting, motherboard will take a series check and test on
systems and peripheral devices. If you set it Enabled, computer startup speed will
improve.
2. Boot up Floppy - Seek
When computer is starting, BIOS will check whether Floppy is available. If you
choose Enabled, when BIOS find no floppy, it will prompt you that is wrong.
3. Boot up NumLock – Status
Generally, the small keyboard in the right side of big keyboard is used as number
keys default. If it is necessary, you can set it OFF, and small keyboard would
become direction keys.
4. Security Option
There are two options between Security Option, if you set it as “Setup”, no
password is needed to login computer, but password is needed to enter CMOS,
which is set before. And only supervisor password could change parameters for
CMOS. If you set it as “System”, you will need computer logon password, and only
supervisor password could modify CMOS.

4. How to set password in CMOS?
Two kinds of password settings are provided in CMOS for user, Supervisor/User
Password). Follow the below:
1. Choose Supervisor Password on main interface, press Enter and
“Enter Password:” appears.
2. The length of password could not be longer than 8 characters. When
you finish typing it, press Enter.
3. Confirm Password now. Type password you just input and
press Enter to make sure.
Tips: When you set Security Option as “System”, you can type one of Supervisor
password or User password to access Windows computer. And please remember
back to main interface and press F10 and Enter to save these changes.
BIOS is one EPROM or EEPROM chip on computer motherboard. BIOS Setup
program is stored in it, which saves important system information and system
parameter.
Actually, BIOS is Basic Input-Output system in microcomputer, whose content is
integrated in a chip on microcomputer motherboard. The most important input and
output program of microcomputer, system information setup, POST and bootstrap
program are saved there.
BIOS main function
1. BIOS Interrupt Service Program
It is a programmable interface between software and hardware in microcomputer
system. It makes application software functions appropriate link up to microcomputer
hardware. The management on floppy, disk, CD-ROM, keyboard, displayer is based
on BIOS system interrupt service program. And computer operator could call this
program directly by accessing break point, such as INT5 and INT13 etc.

5. 2. BIOS System Setup Program
This program is used to set parameters for CMOSRAM. Just press boot key when
you start computer and you will enter this program. And this process to set
parameters for CMOS is also called BIOS settings.
3. Electricity Self-Inspection Programs on the POST
When microcomputer is connected with power, POST will check equipment inside
system. Once there is problem in check process, system prompt message will pops
up for computer user.
4. BIOS System Bootstrap Program
After system POST completes, ROMBIOS will search for soft and hard disk drive,
CD-ROM, Network Server according to setup sequence saved in CMOS settings.
Read operational system boot record and give control privilege to boot record. Boot
record will let system boot successfully.
Relationship between BIOS and CMOS
From the above introduction, you can see BIOS and CMOS is inseparable. We have
to set up CMOS through BIOS setup program, and BIOS information is stored in
CMOS. So at most of time, we usually called CMOS setting as BIOS setting. Both of
them are settings on computer hard ware. And setting parameters are saved in
CMOS chip.