393 lines
9.7 KiB
Markdown
393 lines
9.7 KiB
Markdown
# System Calls
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The system API is exposed to user code using the `COP` interrupt.
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The `C` accumulator is loaded with a function number;
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the other registers are loaded with call-specific data (or nothing),
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and any return values are placed in the same registers.
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What follows is a list of the system calls, their numbers, and
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register arguments they take, and what if any values they return.
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The system API is based loosely on, but not compatible with, that of
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CP/M-3 and MSX-DOS 2.
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Most calls return a status code in C. This code has one value, `STATUS_OK`,
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(equal to `0x0000`) which applies to all sxuch calls; this value indicates
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that the call was successful. Any other value will indicate some specific
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error.
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## `0x00`: Terminate with Error Code
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Arguments:
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- `C`: `0x00`
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- `X`: Error code
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Return Values:
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- This call does not return.
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This call exits the calling program, setting the exit status code
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for the system on its way out. Program control will be returned to
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the command shell.
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## `0x01`: Console Input
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Arguments:
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- `C`: `0x01`
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Return Values:
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- `C`: Character read from stdin
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This call reads one character from standard input. If there is no character
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ready, this call waits until there is one. The read character will also be
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echoed to the screen, just as if it had been passed to the Console Output
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call.
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This call traps certain sequences of characters for "terminal control"
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purposes. When this call traps such a character, it outputs nothing an
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continues waiting for another character to be ready.
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## `0x02`: Console Output
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Arguments:
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- `C`: `0x02`
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- `X`: Character to output
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Return Values:
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- None
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This call sends a single chracter to the standard output, which is usually
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the terminal emulator. The character will be parsed by the terminal emulator
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to handle control characters and escape sequences.
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## `0x03`: Direct Console Input
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Arguments:
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- `C`: `0x03`
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Return Values:
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- `C`: Character value or `NULL`
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This call does direct (raw) console input; if there is a character ready, it
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will be read, and if not, `NULL` will be returned.
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## `0x04`: Direct Console Output
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Arguments:
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- `C`: `0x04`
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- `X`: Character value
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Return Values:
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- None
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This call does direct (raw) console output; the value supplied will be treated
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as the value to write to screen memory, and will not be interpreted for terminal
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control.
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## `0x05`: String Output
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Arguments:
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- `C`: `0x05`
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- `X`: Address of string (15:0)
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- `Y`: Address of string (23:16)
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Return Values:
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- None
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This call uses the 0x02 call "Console Output" above to send a `NULL`-terminated
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string to stdout.
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## `0x06`: Buffered Line Input
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Arguments:
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- `C`: `0x06`
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- `X`: Address of buffer (15:0)
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- `Y`: Address of buffer (23:16)
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Return values:
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- `C`: Status code
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This call will read up to 255 characters from stdin, or up to the first newline,
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whichever comes first. While taking input, a simple line editor is presented to
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the user. When the 255th character has been entered into the buffer, any further
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input will be ignored until a newline is entered.
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The newline in the resulting buffer will be replaced with a `NULL` to terminate the
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string.
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## `0x07`: Console Status
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Arguments:
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- `C`: `0x07`
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Return Values:
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- `C`: Status Code
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This call checks stdin for a character to read. If there is none, this call will return
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zero in C; if there is a character ready, it will return nonzero in C.
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## `0x08`: Return Version Number
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Arguments:
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- `C`: `0x08`
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Return Values:
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- `C`: Major version
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- `X`: Minor version
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- `Y`: Micro version
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This call returns the version number of the kernel.
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## `0x09`: Get Date
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Arguments:
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- `C`: `0x09`
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- `X`: Bank of buffer
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- `Y`: Address of buffer
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Return Values:
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- None
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This call fills in the specified buffer with the current date,
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in the following format:
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```
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struct {
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uint16_t year // Current year
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uint8_t month; // 1 = January..12 = December
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uint8_t day; // 1..31
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uint8_t weekday; // 0 = Sunday..6=Saturday
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}
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```
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## `0x0A`: Set Date
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Arguments:
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- `C`: `0x0A`
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- `X`: Bank of buffer
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- `Y`: Address of buffer
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Return Values:
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- `C`: Status code
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Argument Structure:
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```
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struct {
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uint16_t year // Current year
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uint8_t month; // 1 = January..12 = December
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uint8_t day; // 1..31
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uint8_t weekday; // 0 = Sunday..6=Saturday
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};
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```
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This call sets the system date from the data in the argument structure.
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## `0x0B`: Get Time
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Arguments:
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- `C`: `0x0B`
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- `X`: Bank of buffer
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- `Y`: Address of buffer
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Return Values:
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- `C`: Status code
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Argument Structure:
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```
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struct {
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uint8_t hour; // 0..23
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uint8_t minute; // 0..59
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uint8_t second; // 0..59
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};
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```
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This call fills in the specified argument structure with the current time.
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## `0x0C`: Set Time
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Arguments:
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- `C`: `0x0C`
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- `X`: Bank of argument structure
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- `Y`: Address of argument structure
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Return Values:
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- `C`: Status code
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Argument Structure:
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```
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struct {
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uint8_t hour; // 0..23
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uint8_t minute; // 0..59
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uint8_t second; // 0..59
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};
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```
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This call sets the current time from the provided argument structure.
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## `0x0D`: Open File
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Arguments:
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- `C`: `0x0D`
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- `X`: Bank of pathname string
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- `Y`: Address of pathname string
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Return Values:
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- `C`: Status code
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- `X`: File handle
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This call attempts to open the file referred to by the provided `NULL`-terminated
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string, which must contain a fully-qualified pathname -- something of the form
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`[drive]:/[dir]/[dir2]/filename.ext`, such as `sd0:/games/kaboom/readme.ansi`.
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If the file is successfully opened, `C` will contain `STATUS_OK`, and
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the `X` register will contain the file handle. On error, `C` will contain
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a negative value indicating which error has occured.
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## `0x0E`: Close File Handle
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Arguments:
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- `C`: `0x0E`
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- `X`: File handle
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Return Values:
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- `C`: Status code
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This call attempts to close the file referred to by the provided file handle.
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On success, `C` will contain a status code of `STATUS_OK`. On error,
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`C` will contain a negative value, indicating an error has occured.
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## `0x0F`: Duplicate File Handle
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Arguments:
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- `C`: `0x0F`
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- `X`: File handle
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Return Values:
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- `C`: Status code
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- `X`: Duplicate of file handle
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This call attempts to duplicate the provided file handle. The new file handle
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will be exactly identical to the provided one, and either may be used at any time.
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On success, `C` will contain a status code of `STATUS_OK`, and the `X`
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register will contain the duplicate file handle. On error, `C` will
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contain a negative value, indicating an error has occured.
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## `0x10`: Read from File
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Arguments:
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- `C`: `0x10`
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- `X`: Bank of argument block
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- `Y`: Address of argument block
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Return Values:
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- `C`: Status code
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- `X`: Number of bytes actually read
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Argument Structure:
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```
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struct {
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void *dest; // Pointer to the buffer to use.
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uint16_t file; // File handle.
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size_t length; // Maximum number of bytes to read.
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};
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```
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This call attempts to read up to `length` bytes from the file handle `file`, into
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the buffer pointed to by `dest`. On success, `C` will contain `STATUS_OK`,
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and the `X` register will contain the number of bytes actually read. On error, the C
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accumulator will contain a negative value indicating the specific error, and the `X`
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register will contain the number of bytes actually read.
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## `0x11`: Write to File
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Arguments:
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- `C`: `0x11`
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- `X`: Bank of argument block
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- `Y`: Address of argument block
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Return Values:
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- `C`: Status code
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- `X`: Number of bytes actually written
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Argument Structure:
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```
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struct {
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void *src; // Pointer to the buffer to use.
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uint16_t file; // File handle.
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size_t length; // Maximum number of bytes to write.
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};
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```
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This call attempts to write up to `length` bytes to the file handle `file`, from
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the buffer pointed to by `src`. On success, `C` will contain `STATUS_OK`,
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and the `X` register will contain the number of bytes actually written. On error, the C
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accumulator will contain a negative value indicating the specific error, and the `X`
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register will contain the number of bytes actually written.
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## `0x12`: Seek in File
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Arguments:
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- `C`: `0x12`
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- `X`: Seek value
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- `Y`: Seek origin
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- `0x00`: Seek relative to the beginning of the file
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- `0x01`: Seek relative to the current position in the file
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- `0x02`: Seek relative to the end of the file
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Return value:
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- `C`: Status code
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- `X`: New file position (`31:16`)
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- `Y`: New file position (`15:0`)
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This call moves the internal file pointer, the position in the specified file from
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which data can be read or to which data can be written. On success, this call returns
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`STATUS_OK` in `C`, and the new file position in `X` and `Y`. On error, `C` will contain a negative
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value indicating the specific error, and the new file position in `X` and `Y`.
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## `0x13`: Device I/O Control
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This call performs driver-specific functions.
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## `0x14`: Delete File
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Arguments:
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- `C`: `0x14`
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- `X`: Bank of pathname
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- `Y`: Address of pathname
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Return Values:
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- `C`: Status code
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This call attempts to delete the file indicated by the given `NULL`-terminated string,
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which must contain a fully-qualified pathname. On success, this `C` will contain
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`STATUS_OK`. On failure, `C` will contain a negative number indicating the specific
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error.
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## `0x15`: Move File
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Arguments:
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- `C`: `0x15`
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- `X`: Bank of argument structure
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- `Y`: Address of argument structure
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Return Values:
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- `C`: Status code
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Argument Structure:
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```
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struct {
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char *src; // Fully-qualified source pathname.
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char *dest; // Fully-qualified destination pathname.
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};
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```
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This call attempts to move or rename the specified `source` file to `dest`. On success,
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`C` will contain `STATUS_OK`. On error, `C` will contain a negative value indicating the
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specific error.
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