Components of a Computer System
The five classic components of a computer are input, output, memory, datapath, and control. Datapath and control are combined and called as the processor.
COMPONENTS OF A COMPUTER SYSTEM
The five classic components of a computer are input, output, memory, datapath, and control. Datapath and control are combined and called as the processor. The figure 1.1 shows the standard organization of a computer. This organization is independent of hardware technology.
The organization of a computer, showing the five classic components.
1. Input writes data to memory
2. Output reads data from memory
3. Memory stores data and programs
4. Control sends the signals that determine the operations of the datapath, memory, input, and output.
5. Datapath performs arithmetic and logic operations
Two key components of computers:
1. Input devices, such as the keyboard and mouse,
2. Output devices, such as the screen.
As the names suggest, input feeds the computer, and output is the result of computation sent to the user. Some devices, such as networks and disks, provide both input and output to the computer.
The most commonly used input device is a keyboard. Whenever the user presses a key the control signal be sent to the processor. The processor respond for that by displaying the corresponding character on the display.
The next commonly used input device is a mouse.The original mouse was electromechanical and used a large ball. When it is rolled across a surface, it would cause an x and y counter to be incremented. The amount of increase in each counter told how far the mouse had been moved.
The electromechanical mouse has been replaced by the optical mouse. The optical mouse is actually a miniature optical processor including an LED to provide lighting, a tiny black-and-white camera, and a simple optical processor. The LED illuminates the surface underneath the mouse; the camera takes 1500 sample pictures a second under the illumination. Successive pictures are sent to a simple optical processor that compares the images and determines whether the mouse has moved and how far.
The most fascinating I/O device is probably the graphics display. Most personal mobile devices use liquid crystal displays (LCDs) to get a thin, low-power display. The LCD is not the source of light; instead, it controls the transmission of light. A typical LCD includes rod-shaped molecules in a liquid that form a twisting helix that bends light entering the display, from either a light source behind the display or less often from reflected light.
Today, most LCD displays use an active matrix that has a tiny transistor switch at each pixel to precisely control current and make sharper images. As in a CRT, a red-green-blue mask associated with each pixel determines the intensity of the three color components in the final image; in a color active matrix LCD, there are three transistor switches at each pixel.
The computer hardware supports a refresh buffer, or frame buffer, to store the bit map. The image to be represented on-screen is stored in the frame buffer, and the bit pattern per pixel is read out to the graphics display at the refresh rate.
Pixel - The smallest individual picture element. Screen are composed of hundreds of thousands to millions of pixels, organized in a matrix.
Each coordinate in the frame buffer on the left determines the shade of the corresponding coordinate for the raster scan CRT display on the right. Pixel (X0, Y0) contains the bit pattern 0011, which is a lighter shade of gray on the screen than the bit pattern 1101 in pixel (X1, Y1).
Central processor unit (CPU) - Also called processor. The active part of the computer, which contains the datapath and control and which adds numbers, tests numbers, signals I/O devices to activate, and so on. The processor gets instructions and data from memory.
Removable storage technologies: