System Startup initialization
View /arch/i386/kernel/head.s it is make some architecture specific setup and proceed the main() routine in /init/main.c
Memory Management
/arch/*/mm it is directory for memory management.
Page fault handling code is in /mm/memory.c
Memory maping cache code in /mm/filemap.c
Swap cache is applied in /mm/swap.c
And buffer cache is applied in /mm/buffer.c
Kernel
/arch/*/kernel::it is directory
/kernel/sched.c ::kernel scheduler directory
/kernel/fork.c::fork codedirectory
/include/linux/interrupt.h::Bottom half handling code directory
/include/linux/sched.h::task_struct date structure directory
PCI
/drivers/pci/pci,c::PCI pseudo driver directory
/include/linux/pci.h::system wide definition directory
Interposes Communication
System V IPC object s has an ipc_term data structure present in /include/linux/ipc.h
ipc/msg.c:: system v messages are present
/ipc/shm.c::shared memory and semaphore directory
/ipc/pipes.c:: pipes are applied