BASIC ROM

BASIC ROM is an 8 kB ROM circuit which, under the default bankswitching conditions is "mapped into" the C-64's memory map in the range 40960–49151/$A000–$BFFF: It holds the Commodore BASIC V2 that is available to the system at power-up, allowing the user to start issuing BASIC commands and entering BASIC programs right away.

Strictly speaking, the BASIC takes up a tad over 9 kB; a good kB of it actually resides at the beginning of the KERNAL ROM. This is perfectly "safe" because the bankswitching mechanism cannot enable BASIC ROM whilst at the same time disabling KERNAL.