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The Big Picture

Figure 1 is a function call diagram that describes the kernel's startup procedure. As it shows, kernel initialization proceeds through a number of distinct phases, starting with basic hardware initialization and ending with the kernel's launching of /bin/init and other user programs. The dashed line in the figure shows that init() is invoked as a kernel thread, not as a function call.

Figure 1. The kernel's startup procedure.

Figure 2 is a flowchart that provides an even more generalized picture of the boot process, starting with the bootloader extracting and running the kernel image, and ending with running user programs.

Figure 2. The kernel's startup procedure, in less detail.

The following sections describe each of these function calls, including examples taken from the Hitachi SH7750/Sega Dreamcast version of the kernel.