The basic power-on sequence

To turn on your computer, locate the power button — usually a circle or rectangle on the front or side of the tower, or on the keyboard if you have a laptop. Press and hold it for one to two seconds, then release. You do not need to hold it down; a brief press is enough. The computer will start its boot sequence, which means it is loading the operating system from storage into memory so you can use it.

After you press the button, you will see lights come on inside the tower or on the laptop, and you may hear the fan spin up. The screen will remain black or dark for 10 to 30 seconds while the system initializes. This is normal. Do not press the button again during this time, as that can interrupt the startup and cause problems.

On a desktop computer, make sure the monitor (the screen) is also powered on. Many monitors have their own power button, usually on the front or back. If the monitor stays dark after the tower starts up, check that it is switched on and that the cable connecting it to the tower is plugged in firmly at both ends.

Key Takeaways

  • Press the power button once and release — you do not need to hold it down for more than a second or two.
  • The screen will stay dark for 10 to 30 seconds while the operating system loads; this is normal and you should not press the button again.
  • On a desktop, the monitor has its own power button and must be switched on separately from the tower.
  • If the screen stays dark after 30 seconds, check that the monitor is powered on and that its cable is plugged in at both ends.

What happens during startup

When you press the power button, the computer runs through a series of checks called the boot sequence. First, it tests the hardware — the processor, memory, and storage — to make sure everything is connected and working. Then it loads the operating system (Windows, macOS, or Linux) from the hard drive or solid-state drive into the computer's working memory. This process usually takes 30 seconds to two minutes, depending on how old the computer is and how much software is installed.

During this time, you may see text on the screen, a logo, or a loading bar. Some computers show nothing at all until the operating system is fully loaded. Once the operating system is ready, you will see the login screen (if the computer is password-protected) or the desktop (if it is not). At this point, the startup is complete and you can use the computer.

Logging in after startup

If your computer shows a login screen, you will need to enter your password or PIN to access the desktop. On Windows, click on your username if more than one account exists on the computer, then type your password and press Enter. On a Mac, type your username and password, then press Enter. If you have a fingerprint or face recognition set up, you may be able to use that instead of typing a password.

If you forget your password, you have a few options depending on your operating system. Windows computers can sometimes use a password reset disk or a recovery email address. Mac computers can use your Apple ID to reset the password. If neither of those works, you may need to contact the person who set up the computer or take it to a technician who can help you regain access.

Troubleshooting a computer that will not start

If you press the power button and nothing happens — no lights, no fan noise, no screen activity — the computer is not receiving power. Check that the power cable is plugged into the wall outlet and that the outlet itself works. You can test the outlet by plugging in a lamp or phone charger; if that device powers on, the outlet is fine. If the outlet is dead, try a different outlet in another room. If the computer still does not start, the power supply inside the tower may have failed and will need to be replaced by a technician.

If the lights and fan come on but the screen stays completely black after two minutes, the monitor may not be receiving a signal. First, make sure the monitor is powered on and that the cable connecting it to the tower is plugged in firmly. If you have a desktop with a separate graphics card (a component that handles video), the cable may need to be plugged into the graphics card instead of the motherboard. Try unplugging the monitor cable and plugging it back in, then wait another 30 seconds. If the screen remains black, the graphics card or monitor may need to be checked by a technician.

Restarting versus shutting down

A restart is different from a full shutdown. When you restart, the computer shuts down the operating system and when ready boots back up without cutting power to the hardware. A restart clears temporary files from memory and can fix minor software problems. A shutdown cuts power completely and is useful when you are done using the computer for the day or when you need to move it or work on its hardware.

To restart on Windows, click the Start menu, select the power icon, and choose Restart. On a Mac, click the Apple menu, select Shut Down, and check the box that says "Reopen windows when logging back in" if you want your programs to open automatically after the restart. If the computer is frozen and will not respond to mouse or keyboard input, you can force a restart by holding the power button down for 10 seconds until the computer shuts off, then pressing it again to turn it back on. Avoid doing this regularly, as it can cause data loss or file corruption.

Frequently Asked Questions

How long should I wait before the screen shows something?

Most computers show something on screen within 10 to 30 seconds — either a logo, text, or a loading bar. If the screen is completely black after 30 seconds, wait another minute before assuming something is wrong. Older computers or those with many programs installed can take up to two minutes to fully boot.

Is it bad to turn off the computer by holding the power button?

Holding the power button forces the computer to shut down without closing programs or saving files properly. This can corrupt data and damage the file system. Use the shutdown option in the operating system instead. Only use the force shutdown method if the computer is completely frozen and will not respond to any input.

Why does my computer take so long to start up?

Startup time depends on the age of the hard drive, the amount of software installed, and how many programs are set to run automatically when the computer starts. Older mechanical hard drives are slower than newer solid-state drives. If startup is taking more than three minutes, a technician can check whether the hard drive is failing or whether too many background programs are running.

Do I need to shut down my computer every day?

Modern computers are designed to run for long periods and can be left on or put into sleep mode. Sleep mode uses very little power and lets you resume work when ready without waiting for startup. Shutting down completely is useful if you will not use the computer for several days or if you want to save electricity. There is no harm in either approach.