The first array is for unmodified F keys the second is used when a shifted F

The first array is for unmodified f keys the second

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since modern PC keyboards have twelve F-keys. The first array is for unmodified F-keys, the second is used when a shifted F-key is detected. They are composed of elements of type obs_t, which is a structure that can hold a process number and an integer. This structure and these arrays are declared in keyboard.c on lines 15279 to 15281. Initialization stores a special value, symbolically represented as NONE, in the proc_nr component of the structure to indicate it is not in use. NONE is a value outside the range of valid process numbers. Note that the process number is not a pid, it identifies a slot in the process table. This terminology may be confusing. But to send a notification a process number rather than a pid is used, because process numbers are used to index the priv table which determines whether a process is allowed to receive notifications. The integer events is also initially set to zero. It will be used to count events. The next three functions are all rather simple. Kbd_loadmap (line 15610) is almost trivial. It is called by do_ioctl in tty.c to do the copying of a keymap from user space to overwrite the default keymap. The default is compiled by the inclusion of a keymap source file at the start of keyboard.c. From its first release, MINIX has always provided for dumps of various kinds of system information or other special actions in response to pressing the function keys F1, F2, etc., on the system console. This is not a service generally provided in other operating systems, but MINIX was always intended to be a teaching tool. Users are encouraged to tinker with it, which means users may need extra help for debugging. In many cases the output produced by pressing one of the F-keys will be available even when the system has crashed. Figure 3-43 summarizes these keys and their effects. Figure 3-43. The function keys detected by func_key(). (This item is displayed on page 356 in the print version) Key Purpose F1 Kernel process table F2 Process memory maps F3 Boot image F4 Process privileges F5 Boot monitor parameters F6 IRQ hooks and policies F7 Kernel messages F10 Kernel parameters F11 Timing details (if enabled)
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Figure 3-43. The function keys detected by func_key(). (This item is displayed on page 356 in the print version) Key Purpose F12 Scheduling queues SF1 Process manager process table SF2 Signals SF3 File system process table SF4 Device/driver mapping SF5 Print key mappings SF9 Ethernet statistics (RTL8139 only) CF1 Show key mappings CF3 Toggle software/hardware console scrolling CF7 Send SIGQUIT, same effect as CTRL-\ CF8 Send SIGINT, same effect as CTRL-C CF9 Send SIGKILL, same effect as CTRL-U These keys fall into two categories. As noted earlier, the CTRL-F1 through CTRL-F12 key combinations are detected by kb_read. These trigger events that can be handled by the terminal driver. These events are not necessarily display dumps. In fact, currently only CTRL-F1 provides an information display; it lists function key bindings. CTRL-F3 toggles hardware and software scrolling of the console screen, and the others cause signals.
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