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Typical PC hardware

Typical PC hardware


Hardware of Personal Computer.
1. Monitor
2. Motherboard
3. CPU
4. RAM Memory
5. Expansion card
6. Power supply
7. CD-ROM Drive
8. Hard Disk
9. Keyboard
10. Mouse


Inside a custom computer.
Though a PC comes in many different form factors, a typical personal computer consists of a case or chassis in a tower shape (desktop) and the following parts:

Motherboard

Components directly attached to the motherboard include:
  • The central processing unit (CPU) performs most of the calculations which enable a computer to function, and is sometimes referred to as the "brain" of the computer. It is usually cooled by a heat sink and fan.
  • The chipset mediates communication between the CPU and the other components of the system, including main memory.
  • RAM Stores all running processes (applications) and the current running OS. RAM Stands for Random Access Memory
  • The BIOS includes boot firmware and power management. The Basic Input Output System tasks are handled by operating system drivers.
  • Internal Buses connect the CPU to various internal components and to expansion cards for graphics and sound.
    • Current
      • The northbridge memory controller, for RAM and PCI Express
        • PCI Express, for expansion cards such as graphics and physics processors, and high-end network interfaces
      • PCI, for other expansion cards
      • SATA, for disk drives




Obsolete
      • ATA (superseded by SATA)
      • AGP (superseded by PCI Express)
      • VLB VESA Local Bus (superseded by AGP)
      • ISA (expansion card slot format obsolete in PCs, but still used in industrial computers)
  • External Bus Controllers support ports for external peripherals. These ports may be controlled directly by the southbridge I/O controller or based on expansion cards attached to the motherboard through the PCI bus.

Power supply

Includes power cords, switch, and cooling fan. Supplies power at appropriate voltages to the motherboard and internal disk drives. It also converts alternating current to direct current and provides different voltages to different parts of the computer.

Video display controller

Main article: Graphics card
Produces the output for the computer monitor. This will either be built into the motherboard or attached in its own separate slot (PCI, PCI-E, PCI-E 2.0, or AGP), in the form of a graphics card.
Most video cards support the most basic requirements, and video card manufacturing companies are doing a good job of keeping up with the requirements the games need. However the games are still evolving faster than the video because of manufacturing companies.

Removable media devices

Main article: Computer storage
  • CD (compact disc) - the most common type of removable media, suitable for music and data.
    • CD-ROM Drive - a device used for reading data from a CD.
    • CD Writer - a device used for both reading and writing data to and from a CD.
  • DVD (digital versatile disc) - a popular type of removable media that is the same dimensions as a CD but stores up to 12 times as much information. It is the most common way of transferring digital video, and is popular for data storage.
    • DVD-ROM Drive - a device used for reading data from a DVD.
    • DVD Writer - a device used for both reading and writing data to and from a DVD.
    • DVD-RAM Drive - a device used for rapid writing and reading of data from a special type of DVD.
  • Blu-ray Disc - a high-density optical disc format for data and high-definition video. Can store 70 times as much information as a CD.
    • BD-ROM Drive - a device used for reading data from a Blu-ray disc.
    • BD Writer - a device used for both reading and writing data to and from a Blu-ray disc.
  • HD DVD - a discontinued competitor to the Blu-ray format.
  • Floppy disk - an outdated storage device consisting of a thin disk of a flexible magnetic storage medium. Used today mainly for loading RAID drivers.
  • Iomega Zip drive - an outdated medium-capacity removable disk storage system, first introduced by Iomega in 1994.
  • USB flash drive - a flash memory data storage device integrated with a USB interface, typically small, lightweight, removable, and rewritable. Capacities vary, from hundreds of megabytes (in the same ballpark as CDs) to tens of gigabytes (surpassing, at great expense, Blu-ray discs).
  • Tape drive - a device that reads and writes data on a magnetic tape, used for long term storage and backups.

Internal storage

Hardware that keeps data inside the computer for later use and remains persistent even when the computer has no power.
  • Hard disk - for medium-term storage of data.
  • Solid-state drive - a device similar to hard disk, but containing no moving parts and stores data in a digital format.
  • RAID array controller - a device to manage several internal or external hard disks and optionally some peripherals in order to achieve performance or reliability improvement in what is called a RAID array.

Sound card

Main article: Sound card
Enables the computer to output sound to audio devices, as well as accept input from a microphone. Most modern computers have sound cards built-in to the motherboard, though it is common for a user to install a separate sound card as an upgrade. Most sound cards, either built-in or added, have surround sound capabilities.

Other peripherals

Main article: Peripheral
In addition, hardware devices can include external components of a computer system. The following are either standard or very common.

Wheel Mouse
Includes various input and output devices, usually external to the computer system.

Input

Main article: Input
  • Text input devices
    • Keyboard - a device to input text and characters by depressing buttons (referred to as keys), similar to a typewriter. The most common English-language key layout is the QWERTY layout.
    • Mouse - a pointing device that detects two dimensional motion relative to its supporting surface.
    • Optical Mouse - a newer technology that uses lasers, or more commonly LEDs to track the surface under the mouse to determine motion of the mouse, to be translated into mouse movements on the screen.
    • Trackball - a pointing device consisting of an exposed protruding ball housed in a socket that detects rotation about two axes.
  • Gaming devices
    • Joystick - a general control device that consists of a handheld stick that pivots around one end, to detect angles in two or three dimensions.
    • Gamepad - a general handheld game controller that relies on the digits (especially thumbs) to provide input.
    • Game controller - a specific type of controller specialized for certain gaming purposes.
  • Image, Video input devices
    • Image scanner - a device that provides input by analyzing images, printed text, handwriting, or an object.
    • Webcam - a low resolution video camera used to provide visual input that can be easily transferred over the internet.
  • Audio input devices
    • Microphone - an acoustic sensor that provides input by converting sound into electrical signals.
Imaginary Memory

 An imaginary memory area supported by some operating systems (for example, Windows but not DOS) in conjunction with the hardware. You can think of virtual memory as an alternate set of memory addresses. Programs use these virtual addresses rather than real addresses to store instructions and data. When the program is actually executed, the virtual addresses are converted into real memory addresses.
The purpose of virtual memory is to enlarge the address space, the set of addresses a program can utilize. For example, virtual memory might contain twice as many addresses as main memory. A program using all of virtual memory, therefore, would not be able to fit in main memory all at once. Nevertheless, the computer could execute such a program by copying into main memory those portions of the program needed at any given point during execution.
To facilitate copying virtual memory into real memory, the operating system divides virtual memory into pages, each of which contains a fixed number of addresses. Each page is stored on a disk until it is needed. When the page is needed, the operating system copies it from disk to main memory, translating the virtual addresses into real addresses.
The process of translating virtual addresses into real addresses is called mapping. The copying of virtual pages from disk to main memory is known as paging or swapping.
A fixed amount of data.
(2) In word processing, a page of text. Most text-processing applications recognize a hierarchy of components, starting with a character at the lowest level, followed by a word, a line, a paragraph, and a page. Applications permit certain operations for each type of component; for example, you can delete a character, a word, a line, and sometimes an entire page. For pages, you can also specify formatting characteristics (for example, page size, margins, and number of columns).
(3) In virtual memory systems, a page is a fixed number of bytes recognized by the operating system.
(4) Short for Web page.
(v.) (1) To display one page (or screenful) of a document at a time. To contrast, see scroll.
(2) To copy a page of data from main memory to a mass storage device, or vice versa. Paging is one form of swapping.
A technique used by virtual memory operating systems to help ensure that the data you need is available as quickly as possible. The operating system copies a certain number of pages from your storage device to main memory. When a program needs a page that is not in main memory, the operating system copies the required page into memory and copies another page back to the disk. One says that the operating system pages the data. Each time a page is needed that is not currently in memory, a page fault occurs. An invalid page fault occurs when the address of the page being requested is invalid. In this case, the application is usually aborted.
This type of virtual memory is called paged virtual memory. Another form of virtual memory is segmented virtual memory.
A technique used by virtual memory operating systems to help ensure that the data you need is available as quickly as possible. The operating system copies a certain number of pages from your storage device to main memory. When a program needs a page that is not in main memory, the operating system copies the required page into memory and copies another page back to the disk. One says that the operating system pages the data. Each time a page is needed that is not currently in memory, a page fault occurs. An invalid page fault occurs when the address of the page being requested is invalid. In this case, the application is usually aborted.
This type of virtual memory is called paged virtual memory. Another form of virtual memory is segmented virtual memory.
Physical memory
Also referred to as the physical storage or the real storage, physical memory is a term used to describe the total amount of memory installed in the computer. For example, if the computer has two 64MB memory modules installed, it has a total of 128MB of physical memory.
  • Physical memory is the amount of memory that is derived from hardware. This is typically the RAM modules that are installed onto the motherboard.

    Another type of memory is virtual memory, that is derived from the operating system's use of the harddisk to temporarily write and read information to simulate a larger memory capacity.
Physical memory refers to the storage capacity of the actual hardware, usually referring to the banks microchips on RAM sticks. This is the capacity of the 1's and 0's that can be operated independently of each other.
"Physical Memory" refers to RAM.
RAM.
Computers need a place to run and juggle programs around temporarily, this area is called Random Access Memory and is physically unaltered or clean when you switch off your pc, unlike hard disks and DVD re-writers that actually change or write information on a disk.

RAM is often found in banks of microchips located in long thin sockets on a computer motherboard, sometimes one, not often more than four sockets, these DDR Memory (Double Data Rate?) or DIMM (Dynamic In line Memory Module?) sockets can be upgraded to help boost performance on a computer.

Physical memory is the amount of RAM in your computer.
If you can touch it, (go on open up the side and feel that RAM) it's real if you can't then it can't really exist!
Can it?
Primary storage, presently known as memory, is the only one directly accessible to the CPU. CPU continuously reads instructions stored there and executes them. Any data actively operated on is also stored there in uniform manner.

i hope it helps!
Physical memory is stored on RAM chips on memory cards in the main board of your PC

Virtual memory is when the hard disk simulates memory (much slower)
    • 2 years ago

OVERVIEW OF PHYSICAL AND VIRTUAL MEMORY

The memory management system is designed to make memory resources available safely and efficiently among threads and processes:
  • It provides a complete address space for each process, protected from all other processes.
  • It enables program size to be larger than physical memory.
  • It decides which threads and processes reside in physical memory and manipulates threads and processes in and out of memory.
  • It manages the parts of the virtual address space of a thread or process not in physical memory and determines what portions of the address space should reside in physical memory.
  • It allows efficient sharing of memory between processes.
The data and instructions of any process (a program in execution) or thread of execution within a process must be available to the CPU by residing in physical memory at the time of execution.
To execute a process, the kernel creates a per-process virtual address space that is set up by the kernel; portions of the virtual space are mapped onto physical memory. Virtual memory allows the total size of user processes to exceed physical memory. Through "demand paging", HP-UX enables you to execute threads and processes by bringing virtual pages into main memory only as needed (that is, "on demand") and pushing out portions of a process's address space that have not been recently used.
The term "memory management" refers to the rules that govern physical and virtual memory and allow for efficient sharing of the system's resources by user and system processes.
The system uses a combination of pageout and deactivation to manage physical memory. Paging involves writing recently unreferenced pages from main memory to disk from time to time. A page is this smallest unit of physical memory that can be mapped to a virtual address with a given set of access attributes. On a loaded system, total unreferenced pages might be a large fraction of memory.
Deactivation takes place if the system is unable to maintain a large enough free pool of physical memory. When an entire process is deactivated, the pages associated with the process can be written out to secondary storage, since they are no longer referenced. A deactivated process cannot run, and therefore, cannot reference its data.
Secondary storage supplements physical memory. The memory management system monitors available memory and, when it is low, writes out pages of a process or thread to a secondary storage device called a swap device. The data is read from the swap device back into physical memory when it is needed for the process to execute.
Pages
Pages are the smallest contiguous block of physical memory that can be allocated for storing data and code. Pages are also the smallest unit of memory protection. The page size of all HP-UX systems is four kilobytes.
On a PA-RISC system, every page of physical memory is addressed by a physical page number (PPN), which is a software "reduction" of the physical page number from the physical address. Access to pages (and thus to the data they contain) are done through virtual addresses, except under specific circumstances.[1]
Virtual Addresses
When a program is compiled, the compiler generates virtual addresses for the code. Virtual addresses represent a location in memory. These virtual addresses must be mapped to physical addresses (locations of the physical pages in memory) for the compiled code to execute. User programs use virtual addresses only.
The kernel and the hardware coordinate a mapping of these virtual and physical addresses for the CPU, called "address translation," to locate the process in memory.
A PA-RISC virtual address consists of a space identifier (SID) and an offset.
  • Each space ID represents a 4 GB unit of virtual memory.
  • The offset portion of a virtual address is the offset into this space.
Table 1-1 Format of a 48-bit virtual address
Space ID(16 bits) Offset(32 bits)


Every process running on a PA-RISC processor shares a 48-bit (or larger, depending on HP-PA architecture version) global virtual address space with the kernel and with all other processes running on that machine. Although any process can create and attempt to read or write any virtual address, the kernel uses page granularity access control mechanisms to prevent unwanted interference between processes.
When a virtual page is "paged" into physical memory, free physical pages are allocated to it from the free list. These pages may be randomly scattered throughout the memory depending on their usage history. Translations are needed to tell the processor where the virtual pages are loaded. The process of translating the virtual into physical address is called virtual address translation.
Potentially the virtual address space can be much greater than the physical address space. The virtual memory system enables the CPU to execute programs much larger than the available physical memory and allows you run many more programs at a time than you could without a virtual memory system.

Demand Paging

For a process to execute, all the structures for data, text, and so on have to be set up. However, pages are not loaded in memory until they are "demanded" by a process -- hence the term, demand paging. Demand paging allows the various parts of a process to be brought into physical memory as the process needs them to execute. Only the working set of the process, not the entire process, need be in memory at one time. A translation is not established until the actual page is accessed.

[1] When virtual translation must be turned off (the D and I bits are off), pages are accessed by their absolute addresses.


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