Feb 19
The Monochrome Display Adapter (MDA), also card MDA or Monocrhome Display and Printer Adapter (MDPA), was introduced in 1981. Along with the card CGA, was the first card standards of exhibition of video for computer IBM PC and the clones. The MDA did not have graphics modes, offered only a single monochrome text mode (the way of video 7), that could exhibit 80 columns by 25 lines of characters of hi-res text in a monitor TTL that showed the green and black image in. Card MDA, like the CGA, used the controller Motorola 6845 to generate the image.
Feb 19
The Color Graphics Adapter (Graphics adapter in Color) or CGA, commercialized in 1981, was the first card color graphics of IBM (originally call “Color/Graphics Adapter Monitor”), and the first standard color graphics for IBM PC. When IBM introduced in the market its PC in 1981, the standard CGA, in spite of to have appeared at the same time, was little used in the beginning, since most of the buyers they acquired a PC for professional use. For games there were other much more popular computers, and then it was not considered that the color graphics had another use that the purely playful one. Consequently, many of the first buyers of the PC decided on MDA (Monochrome Display Adapter), that only allowed the text visualization. In 1982 the Hercules Graphics Card was commercialized, that allowed to show graphs in monochrome a resolution much greater than the CGA, in addition to being more compatible with the MDA, which still harmed more the sales of the CGA. Everything changed in 1984 when IBM introduced PC AT and Enhanced Graphics Adapter (EGA). With it, the price of the old card CGA lowered considerably and it became an interesting alternative of low cost, reason why the new companies dedicated to the clónicos manufacture of PCs adopted it quickly. PCs not-AT of low cost with cards CGA was sold very well in the following years, and as consequence many games were published for them in spite of their limitations. The popularity of the CGA began to disappear when 1987 card VGA became the new solution of high level, being relegated the EGA to the PCs of low cost. The standard card IBM CGA incorporated 16 kilobytes of VRAM, and allowed to show several graphics modes and of text. The Maxima resolution of any way was 640×200, and the greater depth of supported color was of 4 bits (16 colors). The way well-known, used more in most of the games CGA, showed 4 colors a resolution of 320×200. Although the 4 colors were considered generally like the limit for the card CGA, was possible to increase that amount by means of several methods (some officials, others not).
Feb 19
different adapters of class and objects have trade-off * A class adapter: or It adapts Adaptee to Target ordering to concrete a Adaptee class. Like consequence, a adaptadora class will not work when it is desired to adapt a class and all its subclasses. or It allows the Adapter to sobrescribir something of behavior of Adaptee, since Adapter is a subclass of Adaptee. * An object adapter: or It by itself allows that an only Adapter works with many Adaptees, that is to say, to the Adapter and the subclasses (if it is that it has it). The Adapter also can add functionality to all the Adaptees of a single time. or For difficult to sobrescribir the behavior of Adaptee. This will require to derive Adaptee and to cause that Adapter talks about to the subclass in place that to the Adaptee by itself. Here there are other questions to consider when the Adapter pattern is used: * 1. Whichever adaptation makes the Adapter? Adapter varies in the amount of work that makes to adapt Adaptee to the Target interface. There is a phantom of possible work, from a simple conversion (for example, changing the names of the operations) to supporting a set of entirely different operations. The amount of work that Adapter does depends on whatever of similar have the Target interface with Adaptee. * 2.Adaptadores Pluggables a class is reusable when minimizás the supposition that other classes must make to use it. By means of the construction in a class of the adaptation of an interface, you eliminate the supposition of which other classes see the same interface. Position of another way, the adaptation of the interface allows us to incorporate nuesta class in existing systems that can wait for different interfaces for the class.