// Routines from C64 KERNAL ROM

// CHROUT. Write byte to default output. (If not screen, must call OPEN and CHKOUT beforehands.)
// Input: A = Byte to write.
asm void chrout(byte register(a) char) !preserves_a !preserves_x !preserves_y @$FFD2 extern

// CHRIN. Read byte from default input (for keyboard, read a line from the screen). (If not keyboard, must call OPEN and CHKIN beforehands.)
// Output: A = Byte read.
asm byte chrin() @$FFCF extern
alias getchar = chrin

// CHKIN. Define file as default input. (Must call OPEN beforehands.)
// Input: X = Logical number.
asm void chkin(byte register(x) fd) @$FFC6 extern

// CHKOUT. Define file as default output. (Must call OPEN beforehands.)
// Input: X = Logical number.
asm void chkout(byte register(x) fd) @$FFC9 extern

// CLRCHN. Close default input/output files (for serial bus, send UNTALK and/or UNLISTEN); restore default input/output to keyboard/screen.
asm void clrchn() @$FFCC extern

// READST. Fetch status of current input/output device, value of ST variable. (For RS232, status is cleared.)
// Output: A = Device status.
asm byte readst() @$FFB7 extern

asm void putchar(byte register(a) char) {
    JSR chrout
    LDA #0
    STA $D4
    ? RTS
}

inline void new_line() {
    chrout(13)
}

// OPEN. Open file. (Must call SETLFS and SETNAM beforehands.)
asm void open() @$FFC0 extern

// CLOSE. Close file.
// Input: A = Logical number.
asm void close(byte register(a) fd) @$FFC3 extern

// SETLFS. Set file parameters.
// Input: A = Logical number; X = Device number; Y = Secondary address.
asm void setlfs(byte register(a) fd, byte register(x) device, byte register(y) secondary) @$FFBA extern

// SETNAM. Set file name parameters.
// Input: A = File name length; X/Y = Pointer to file name.
asm void setnam(pointer register(xy) filename, byte register(a) len) @$FFBD extern

// 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).
asm clear_carry load(bool register(a) verify, pointer register(xy) address) @$FFD5 extern

// 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).
asm clear_carry save(byte register(a) address, word register(xy) past_end) @$FFD8 extern

word irq_pointer @$314