hardware and operating systems basics

BY SA

client/workstation (PC) server (responds to requests from network) hand-held (phone, audio player) embedded system (toaster, car) mainframe (a big server) supercomputer (a many-processor system)

RAM (Random Access Memory) addressable by the CPU volatile faster than storage code and data of running programs

programming model (simplified conception of a processor for sake of programmers)

instruction (a sequence of bits understood by the processor to signal a certain action) copy bytes arithmetic bit logic jumps

register (a small memory area in a processor) status general purpose

ISA (Instruction Set Architecture) x86 (IA-32, x86-64) ARM MIPS Motorola 68k

call stack (local variables) call stack (local variables) program memory heap (everything else) heap (everything else) code

frame of main frame of cat frame of dog frame of fish frame of bird frame of lama stack space local variables argument values  top of stack

frame of moose stack space frame of main frame of cat frame of dog frame of fish frame of bird local variables argument values return address  top of stack

big-endian vs. little-endian (the order in which the bytes of a register are copied from registers to memory and vice versa)

big-endian vs. little-endian (the order in which the bytes of a register are copied from registers to memory and vice versa)

processor registers processor cache random access memory hard drives speed, cost capacity

CPU registers device read/write 

port-mapped I/O vs. memory-mapped I/O output register 2 to port 0x44 98 copy register 5 to address 0x66 2C 1A 32

ports memory addresses RAM 0x xFF FF FF FF byte 0 byte n port 0 port n devices

memory addresses RAM 0x x xFF FF FF FF 0x00 00 FF FF byte 0 byte n devices

(code periodically checks device registers to see if the device needs the CPU to do something) polling

CPU registers device interrupt line

(code periodically checks device registers to see if they need the CPU to do something) polling 1.device sends interrupt signal to CPU 2.CPU saves state of whatever it was currently doing 3.CPU jumps to address corresponding to interrupt number in the interrupt table interrupt

0x interrupt 0 0x interrupt 1 0x interrupt 2 0xA interrupt 3 0xFF interrupt 4 0xFF interrupt 5 0xFF interrupt 6 0xFF interrupt 7 ……

(code periodically checks device registers to see if they need the CPU to do something) polling 1.device sends interrupt signal to CPU 2.CPU saves state of whatever it was currently doing 3.CPU jumps to address corresponding to interrupt number in the interrupt table 4.CPU returns to whatever it was doing before the interrupt interrupt

hardware exception (a condition which causes the CPU to jump to a pre-determined address) 0x exception 0 0x exception 1 0x exception 2 0xA exception 3 0xFF exception 4 ……

Instruction Set Architecture byte size word size address size cache speeds and sizes big-endian vs. little-endian ports vs. memory-mapped i/o number of processors/cores

boot firmware CPU registers BIOS

boot firmware CPU registers BIOS

operating system (manages the hardware and running programs) load and manage processes provide “interfaces” to hardware via system calls provide a filesystem provide a basic user interface

Windows (series of OS’s from Microsoft) Windows 7 Windows Server 2008 Windows CE

Unix (a family of OS’s) Linux BSD OS X

OS device driver (plug-in to the OS to control a particular device) device driver software hardware

B B A A B B C C C C B B A A B B A A time A A B B C C B B C C A A C C C C CPU CPU 2 process OS

1.CPU receives interrupt 2.interrupt stores state of currently running code 3.interrupt invokes handler 4.interrupt handler invokes the scheduler 5.scheduler selects a process 6.scheduler “configures” CPU for that process 7.scheduler jumps execution to that process pre-emptive multitasking

Process C Process B OS Process A 0x xFF FF FF FF

stack heap code 0x x FF FF FF FF heap RAM byte 0 byte n

stack heap code 0x x FF FF FF FF heap RAM byte 0 byte n HD

Process C Process B OS Process A jump to system call code via special instruction RAM

0x system call 0 0x system call 1 0x system call 2 0xA system call 3 0xFF system call 4 0xFF system call 5 0xFF system call 6 0xFF system call 7 ……

stack code 0x x FF FF FF FF heap allocated with system call  heap allocated with system call 

stack code 0x x FF FF FF FF heap  deallocated with system call

stack code 0x x FF FF FF FF  top of stack stack boundary  heap

stack code 0x x FF FF FF FF  top of stack stack boundary  heap

created waitingrunning blocked terminated

HD partition 1 partition 2 partition 3 HD partition 4 flash drive partition 5 CD-ROM partition 6 partition 7

file 35 file 7 file 61 file 3 directory 21 directory 86 root directory

partition 1 C:H:H:D:D: C:/ H:/ D:/ partition 2 partition 3

partition 1 C:H:H:D:D: C:/adams/nixon H:/taylor/polk/hayes D:/garfield partition 2 partition 3

partition 1 /banana//lemon/apple partition 2 partition 3

partition 1 /banana//lemon/apple /banana/adams/nixon /taylor/polk/hayes /lemon/apple/garfield partition 2 partition 3

IPC (Interprocess Communication) files pipes sockets signals shared memory