SYS_HALT, /* Halt the operating system. */
SYS_EXIT, /* Terminate this process. */
SYS_WAIT, /* Wait for a child process to die. */
- SYS_YIELD, /* Yield to another process. */
SYS_CREATE, /* Create a file. */
SYS_REMOVE, /* Delete a file. */
SYS_OPEN, /* Open a file. */