A computer checks all internal hardware for compatibility and connection before starting the remainder of the boot process. If the computer passes the POST check, the computer may give a single beep (some computers may beep twice) as it starts and continue to boot. However, if the computer fails the POST check, the computer will either not beep or generate a beep code that tells the user the source of the problem.

BIOS beep codes

Below are some of the BIOS Beep codes that can occur. However, because of the wide variety of different computer manufacturers with this BIOS, the beep codes may vary.
it depends on other factors.

Beep Code
Descriptions
1 Short – DRAM refresh failure
2 Short – Parity circuit failure
3 Short – Base 64 K RAM failure
4 Short – System timer failure
5 Short – Process failure
6 Short – controller Gate A20 error
7 Short – Virtual mode exception error
8 Short – Display memory Read/Write test failure
9 Short – ROM BIOS checksum failure
10 Short – CMOS shutdown Read/Write error
11 Short – Cache Memory error
1 Long, 3 Short – Conventional/Extended memory failure
1 Long, 8 Short – Display/Retrace test failed
Two tone siren – Low CPU Fan speed, Voltage Level issue