1. Internal testing performed when you start or reset your computer. Encoded in read-only memory (ROM) the POST program first checks the microprocessor by having it perform a few simple operations. Then it reads the CMOS ROM, which stores the amount of memory and type of disk drives in your system. Next, the POST writes, then reads, various data patterns to each byte of memory (you can watch the bytes count off on-screen and often end the test with a keystroke); Finally, the POST communicates with every device; you see the keyboard and drive lights flash and the printer resets, for example. The BIOS continues with hardware testing, then looks in drive A for an operating system if drive A isn't found, it looks in drive C. See basic input/output system (BIOS) and boot sector. From QUECID