Lesson 2: Computer System Structure Flashcards
set of integrated devices that input, output, process, and store data and information
Computer System
basic, complete and functional hardware and software setup with everything needed to implement computing performance
Computer System
Four Main Structural Elements of a Computer System (PMIS)
Processor, Main Memory, I/O Modules, System Bus
[Main Structural Elements of a Computer System] controls the operation of the computer and performs data processing functions
Processor
[Main Structural Elements of a Computer System] commonly known as central processing unit (CPU)
Processor
[Main Structural Elements of a Computer System] stores data and programs which is typically volatile
Main Memory
[Main Structural Elements of a Computer System] moves data between the computer and its external environment
I/O Modules
[Main Structural Elements of a Computer System] provides communication among processors, main memory and I/O modules
System Bus
startup sequence that starts the operating system of a computer when it is turned on
Booting
the initial set of operations that the computer performs when it is switched on
Boot Sequence
program whose task is to load a bigger program, such as the operating system
Boot Loader
Stages of Linux Boot Process (BMGKIR)
BIOS
MBR
GRUB
Kernel
Init
Runlevel
What does BIOS stand for?
Basic Input/Output System
What does BIOS do?
—Performs some system integrity checks
—Searches, loads, and executes the boot loader program
—Loads and executes the MBR boot loader
What does MBR stand for?
Master Boot Record
Where is MBR located?
First sector of the bootable disk
Three components of MBR (PPM)
Primary boot loader info (first 446 bytes)
Partition table info (next 64 bytes)
MBR validation check (last 2 bytes)
What does MBR do?
Loads and executes the GRUB boot loader
What does GRUB stand for?
Grand Unified Bootloader
What does GRUB do?
—displays a splash screen, waits for few seconds, if you don’t enter anything, it loads the default kernel image as specified in the grub configuration file
—loads and executes Kernel and initrd images
What does Kernel do?
—mounts the root file system as specified in the “root=” in grub.conf
—executes the /sbin/init program
what does initrd stand for?
Initial RAM Disk
What is initrd?
—used by kernel as temporary root file system until kernel is booted and the real root file system is mounted
—contains necessary drivers compiled inside, which helps it to access the hard drive partitions, and other hardware
What does Init do?
—looks at the /etc/inittab file to decide the Linux run level
—identifies the default initlevel from /etc/inittab and uses that to load all appropriate program
—execute ‘grep initdefault /etc/inittab’ on your system to identify the default run level
Available run levels
0 – halt
1 – Single user mode
2 – Multiuser, without NFS
3 – Full multiuser mode
4 – unused
5 – X11
6 – reboot
What is the default run level?
3 or 5
Stages of Normal PC Boot Process (SBIL)
Startup of PC
BIOS to POST
Identify boot device
Load OS
Categories of Booting Process (HS)
Hard (Cold) Booting
Soft (Warm) Booting
[Categories of Booting Process] when computer starts form the very beginning or completely dead state, can be considered as a self-test power-on mode for computers
Hard (Cold) Booting
[Categories of Booting Process] restarting the computer and allows the system to load OS again, which means that the system is already turned on from the beginning. Mostly, performing asoft boot up when the PC was not shut down properly or in case of anytechnical issuewhile operating it.
Soft (Warm) Booting
Two Fundamental Approaches to OS Interface (CG)
Command-line Interface (CLI)
Graphical User Interface (GUI)
[Two Fundamental Approaches to OS Interface] allows users to directly enter commands to be performed by the operating system
Command-Line Interface (CLI)
[Two Fundamental Approaches to OS Interface] allows users to interface with the operating system via icons or graphics by means of point-and-click operations
Graphical User Interface (GUI)
Some Advantages of GUI (CUM)
CONFIRM: visually acknowledges and confirms each type of activities performed by the users
UNDERSTAND: easy to understand
MULTITASKING: enables the users to perform a number of tasks at the same time
Rough categories of I/O devices (SUCO)
Storage
User Interface
Communications
Other
How devices communicate with the computer
Signals sent over wires or air
How devices connect with the computer
Ports
common set of wires connecting multiple devices
Bus
include rigid protocols for the types of messages that can be sent across the bus and the procedures for resolving contention issues
Bus
Bus Types Commonly Found in a Modern PC (PESD)
PCI Bus
Expansion Bus
SCSI Bus
Daisy-chain Bus
[Bus Types Commonly Found in a Modern PC] connects HIGH-SPEED HIGH-BANDWIDTH DEVICES to the memory subsystem and the CPU
PCI Bus
[Bus Types Commonly Found in a Modern PC] connects SLOWER BANDWIDTH DEVICES, which typically deliver data one character at a time with buffering
Expansion Bus
[Bus Types Commonly Found in a Modern PC] connects a number of SCSI devices to a common SCSI controller
SCSI Bus
[Bus Types Commonly Found in a Modern PC] a string of devices is connected to each other like beads on a chain, and only one of the devices is directly connected to the host
Daisy-chain Bus
Communicate with devices associated with each port
Registers
Registers may be 1-4 bytes in size and may include…? (IOSC)
Data-IN Register
Data-OUT Register
Status Register
Control Register
[Registers] read by the host to get input from the device
Data-in Register
[Register] written by the host to send output
Data-out Register
[Register] has bits read by the host to ascertain the status of the device
Status Register
[Register] has bits written by the host to issue commands or to change settings of the device
Control Register
Another technique for communicating with devices in which certain portion of the processor’s address space is mapped to the device and communications occur by reading and writing directly to/from those memory areas
Memory-Mapped I/O
suitable for devices which must move large quantities of data quickly
Memory-Mapped I/O
can be used either instead of or more often in combination with traditional registers
Memory-Mapped I/O
when does potential problem exists with memory-mapped I/O
if a process is allowed to write directly to the address space used by a memory-mapped I/O device
T or F: The processor (CPU) can load instruction only from memory.
True
Where does general purpose computers run their programs from?
Main memory (RAM)
What is the most common secondary storage?
Magnetic disk
Hierarchy of Storage-Device (RCMS-MOM)
Registers
Cache
Main memory
Solid-state disk
Magnetic disk
Optical disk
Magnetic tapes
