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The motherboard on your computer contains a small program called the BIOS that manages connected hardware components and some low-level operations such as drive boot order. The BIOS works even when no operating system is installed and performs the Power-On Self Test each time you turn on your computer. The system POST uses a combination of screen output and beep codes to inform you of any problems at startup. Processor · Some computers beep once at startup to indicate a central processing unit failure. You can identify a faulty CPU as the cause of one beep if your computer has an AST motherboard and doesn't boot up after making the beep. Other manufacturers could use one beep to mean the CPU failed, and your owner's manual contains the beep codes generated by your motherboard. A processor can fail as a result of continued overheating or a faulty power supply unit. Memory · The main memory in your computer uses a capacitor for each bit of information it stores. Capacitors must be continually refreshed with the current state of a program or the data in them will fade over time. AMI motherboards emit one beep at startup if the dynamic random-access memory fails to refresh. Apple computers beep once at startup if no RAM is installed. If your Apple computer doesn't find any RAM during the POST, it skips the startup chime. On some models, the power light flashes twice. Default Beep · Your operating system uses the system beep from your motherboard to respond to some keyboard input. The sound scheme in Windows includes a mix of sounds from your speakers and motherboard to indicate an event, such as connecting or disconnecting a device or receiving email. Because some computers don't have speakers, Windows uses the system beep to confirm Ease of Access changes, such as enabling Sticky Keys or Filter Keys. Your computer could beep once if you type too quickly or press several keys at the same time. Normal Operation · Most motherboards beep once at startup to tell you that your computer is operating normally. If your computer beeps once before booting your operating system as usual, you may not have a problem. Apple computers beep once as a result of normal operation during a firmware update when you press and hold the power button. If you don't want to hear the startup beep from your motherboard, you may be able to turn it off in the BIOS settings.