Commands
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int open_file(string filename; int type)
void close_file(int handle)
int write_byte(int handle; int byte)
int read_byte(int handle; var int byte)
int write_word(int handle; int word)
int read_word(int handle; var int word)
int write_line(int handle; string line)
int read_line(int handle; var string line)
int write_raw(int handle; string line)
int read_raw(int handle; var string data; int size)
