SCINIT. Initialize VIC; restore default input/output to keyboard/screen; clear screen; set PAL/NTSC switch and interrupt timer.
Input: –
Output: –
Used registers: A, X, Y.
Real address: $FF5B.

IOINIT. Initialize CIA's, SID volume; setup memory configuration; set and start interrupt timer.
Input: –
Output: –
Used registers: A, X.
Real address: $FDA3.

RAMTAS. Clear memory addresses $0002-$0101 and $0200-$03FF; run memory test and set start and end address of BASIC work area accordingly; set screen memory to $0400 and datasette buffer to $033C.
Input: –
Output: –
Used registers: A, X, Y.
Real address: $FD50.

RESTOR. Fill vector table at memory addresses $0314-$0333 with default values.
Input: –
Output: –
Used registers: –
Real address: $FD15.

VECTOR. Copy vector table at memory addresses $0314-$0333 from or into user table.
Input: Carry: 0 = Copy user table into vector table, 1 = Copy vector table into user table; X/Y = Pointer to user table.
Output: –
Used registers: A, Y.
Real address: $FD1A.

SETMSG. Set system error display switch at memory address $009D.
Input: A = Switch value.
Output: –
Used registers: –
Real address: $FE18.

LSTNSA. Send LISTEN secondary address to serial bus. (Must call LISTEN beforehands.)
Input: A = Secondary address.
Output: –
Used registers: A.
Real address: $EDB9.

TALKSA. Send TALK secondary address to serial bus. (Must call TALK beforehands.)
Input: A = Secondary address.
Output: –
Used registers: A.
Real address: $EDC7.

MEMBOT. Save or restore start address of BASIC work area.
Input: Carry: 0 = Restore from input, 1 = Save to output; X/Y = Address (if Carry = 0).
Output: X/Y = Address (if Carry = 1).
Used registers: X, Y.
Real address: $FE25.

MEMTOP. Save or restore end address of BASIC work area.
Input: Carry: 0 = Restore from input, 1 = Save to output; X/Y = Address (if Carry = 0).
Output: X/Y = Address (if Carry = 1).
Used registers: X, Y.
Real address: $FE34.

SCNKEY. Query keyboard; put current matrix code into memory address $00CB, current status of shift keys into memory address $028D and PETSCII code into keyboard buffer.
Input: –
Output: –
Used registers: A, X, Y.
Real address: $EA87.

SETTMO. Unknown. (Set serial bus timeout.)
Input: A = Timeout value.
Output: –
Used registers: –
Real address: $FE21.

IECIN. Read byte from serial bus. (Must call TALK and TALKSA beforehands.)
Input: –
Output: A = Byte read.
Used registers: A.
Real address: $EE13.

IECOUT. Write byte to serial bus. (Must call LISTEN and LSTNSA beforehands.)
Input: A = Byte to write.
Output: –
Used registers: –
Real address: $EDDD.

UNTALK. Send UNTALK command to serial bus.
Input: –
Output: –
Used registers: A.
Real address: $EDEF.

UNLSTN. Send UNLISTEN command to serial bus.
Input: –
Output: –
Used registers: A.
Real address: $EDFE.

LISTEN. Send LISTEN command to serial bus.
Input: A = Device number.
Output: –
Used registers: A.
Real address: $ED0C.

TALK. Send TALK command to serial bus.
Input: A = Device number.
Output: –
Used registers: A.
Real address: $ED09.

READST. Fetch status of current input/output device, value of ST variable. (For RS232, status is cleared.)
Input: –
Output: A = Device status.
Used registers: A.
Real address: $FE07.

SETLFS. Set file parameters.
Input: A = Logical number; X = Device number; Y = Secondary address.
Output: –
Used registers: –
Real address: $FE00.

SETNAM. Set file name parameters.
Input: A = File name length; X/Y = Pointer to file name.
Output: –
Used registers: –
Real address: $FDF9.

OPEN. Open file. (Must call SETLFS and SETNAM beforehands.)
Input: –
Output: –
Used registers: A, X, Y.
Real address: ($031A), $F34A.

CLOSE. Close file.
Input: A = Logical number.
Output: –
Used registers: A, X, Y.
Real address: ($031C), $F291.

CHKIN. Define file as default input. (Must call OPEN beforehands.)
Input: X = Logical number.
Output: –
Used registers: A, X.
Real address: ($031E), $F20E.

CHKOUT. Define file as default output. (Must call OPEN beforehands.)
Input: X = Logical number.
Output: –
Used registers: A, X.
Real address: ($0320), $F250.

CLRCHN. Close default input/output files (for serial bus, send UNTALK and/or UNLISTEN); restore default input/output to keyboard/screen.
Input: –
Output: –
Used registers: A, X.
Real address: ($0322), $F333.

CHRIN. Read byte from default input (for keyboard, read a line from the screen). (If not keyboard, must call OPEN and CHKIN beforehands.)
Input: –
Output: A = Byte read.
Used registers: A, Y.
Real address: ($0324), $F157.

CHROUT. Write byte to default output. (If not screen, must call OPEN and CHKOUT beforehands.)
Input: A = Byte to write.
Output: –
Used registers: –
Real address: ($0326), $F1CA.

LOAD. Load or verify file. (Must call SETLFS and SETNAM beforehands.)
Input: A: 0 = Load, 1-255 = Verify; X/Y = Load address (if secondary address = 0).
Output: Carry: 0 = No errors, 1 = Error; A = KERNAL error code (if Carry = 1); X/Y = Address of last byte loaded/verified (if Carry = 0).
Used registers: A, X, Y.
Real address: $F49E.

SAVE. Save file. (Must call SETLFS and SETNAM beforehands.)
Input: A = Address of zero page register holding start address of memory area to save; X/Y = End address of memory area plus 1.
Output: Carry: 0 = No errors, 1 = Error; A = KERNAL error code (if Carry = 1).
Used registers: A, X, Y.
Real address: $F5DD.

SETTIM. Set Time of Day, at memory address $00A0-$00A2.
Input: A/X/Y = New TOD value.
Output: –
Used registers: –
Real address: $F6E4.

RDTIM. read Time of Day, at memory address $00A0-$00A2.
Input: –
Output: A/X/Y = Current TOD value.
Used registers: A, X, Y.
Real address: $F6DD.

STOP. Query Stop key indicator, at memory address $0091; if pressed, call CLRCHN and clear keyboard buffer.
Input: –
Output: Zero: 0 = Not pressed, 1 = Pressed; Carry: 1 = Pressed.
Used registers: A, X.
Real address: ($0328), $F6ED.

GETIN. Read byte from default input. (If not keyboard, must call OPEN and CHKIN beforehands.)
Input: –
Output: A = Byte read.
Used registers: A, X, Y.
Real address: ($032A), $F13E.

CLALL. Clear file table; call CLRCHN.
Input: –
Output: –
Used registers: A, X.
Real address: ($032C), $F32F.

UDTIM. Update Time of Day, at memory address $00A0-$00A2, and Stop key indicator, at memory address $0091.
Input: –
Output: –
Used registers: A, X.
Real address: $F69B.

SCREEN. Fetch number of screen rows and columns.
Input: –
Output: X = Number of columns (40); Y = Number of rows (25).
Used registers: X, Y.
Real address: $E505.

PLOT. Save or restore cursor position.
Input: Carry: 0 = Restore from input, 1 = Save to output; X = Cursor column (if Carry = 0); Y = Cursor row (if Carry = 0).
Output: X = Cursor column (if Carry = 1); Y = Cursor row (if Carry = 1).
Used registers: X, Y.
Real address: $E50A.

IOBASE. Fetch CIA #1 base address.
Input: –
Output: X/Y = CIA #1 base address ($DC00).
Used registers: X, Y.
Real address: $E500.