Kernal Calls

Official OS calls

The entries below are the official1 Kernal entry points for the Commodore 64.

1 - Except for CLRLN & CLSR which are from the ROM disassembly but are useful.


CLALL Close all open files
CLOSE Close a logical file
LOAD Load memory from a device
OPEN Open a logical file
SAVE Save memory to a device
SETLFS Setup a logical file
SETNAM Set file name


CHKIN Open channel for input
CHKOUT Open channel for output
CHRIN Get a character from the input channel
CHROUT Output a character
CLRCHN Clear I/O channels
READST Read status word

IEEE Serial Bus

ACPTR Get data from the serial bus
CIOUT Transmit a byte over the serial bus
LISTEN Command a device on serial bus to LISTEN
SECOND Send secondary address for LISTEN
SETTMO Set IEEE bus card timeout
TALK Command a device on serial bus to TALK
TKSA Send secondary address to a device commanded to TALK
UNLSN Send an UNLISTEN command
UNTLK Send an UNTALK command


GETIN Get a character
SCNKEY Scan the keyboard
STOP Check if key/stop key is pressed


IOBASE Define I/O memory page
MEMBOT Set bottom of memory
MEMTOP Set top of memory
RAMTAS Perform RAM test


CLRLN Clear the line X
CLSR Clear the screen
PLOT Set cursor location
SCREEN Return screen format
SETMSG Control system message output


CINT Initialise screen editor
IOINIT Initialise I/O Devices
RESTOR Restore default system & interrup vectors
VECTOR Manage RAM Vectors


RDTIM Read system clock
SETTIM Set system clock
UDTIM Update system clock
Last modified November 1, 2021: Start adding the 1541/D64 disk format (ebd206c)