1. Field of the Invention
The present invention relates to a technique for controlling the screen size of a monitor adapted for the environment of a graphic user interface (hereinafter, referred to as a "GUI") between a computer and a user and, more particularly, to a technique for controlling the screen size of a monitor adapted for the GUI environment which is contrived to magnify a part of the screen by using an S-shaped correcting an switching circuit and a correcting port of a horizontal and vertical signal processor in the monitor.
2. Discussion of Related Art
In general human beings can sense graphic data, that is, visual information more rapidly than any other sort of information. For that reason, it may be good if software is visible as other visible objects. A dialogic button controller of Windows utilizing this principle converts conceptual data into visible data. Therefore, data are easily shown when those windows are used, and moreover lots of data can be seen by overlapping the screens. Software utilizing windows is designed to select command words logically by operating the button controller on the monitor screen.
For these reasons, as hardware and software have gradually gotten more complicated and their operating method gets more difficult, a GUI (graphical user interface) operational system has been developed. The GUI operational system provides a computer operation with continuity and convenience as well as simplicity of study.
Those applied programs utilizing the GUI environment can execute more than one program at a time. The applied programs are utilized by dividing CPU time in order. But, this means dividing the time of CPU use, and not simultaneously executing those applied programs. This is because the user cannot sense the speedy conversion of the applied programs by the CPU. The ability to simultaneously perform various functions is called multitasking. An environment for executing the multitasking is called a GUI environment, and is widely distributed recently.
But, a monitor adaptable to the GUI environment has not been developed yet.
In an earlier monitor for multitasking, the video card receives data processed in a central processing unit of a computer and processes the data into video signals including horizontal and vertical synchronization signals and RGB (red, green and blue) video signals.
The RGB signals are fed to a video preamplifier which in turn is fed to a video output amplifier which in turn feeds a cathode ray tube.
The horizontal and vertical synchronizing signals are fed to a microcomputer as well as to a horizontal and vertical oscillator signal processor. The horizontal and vertical oscillator signal processor provides an output to a horizontal driving circuit which in turn drives a horizontal output circuit driving a horizontal deflection yoke. The horizontal and vertical oscillator processor also provides an output to a vertical output circuit which drives a vertical deflection yoke. An automatic frequency control circuit provides control signals both to the horizontal and vertical oscillator signal processor and the horizontal output circuit.
An S correcting circuit receives an S-shaped correction signal from the microcomputer and supplies the S-shaped correction signals to the horizontal output circuit to correct the distortion of the monitor screen.
In such a monitor, during multitasking in the GUI environment, various programs are executed at the same time by using multiple windows. However, the monitor does not provide a circuit which magnifies a certain portion of on the monitor screen using hardware.