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In ladbrokespoker.com computing, Mode 13h is a standard 256 colour mode on International ladbrokespoker.com ladbrokespoker.com Business Machines VGA graphics hardware. It features a resolution of 320×200 pixels and was used extensively in computer games of the late 1980s and early- to mid-1990s. Mode 13h provides a straight forward manner of access to ladbrokespoker.com video at the expense of several very useful features. Due to its aspect ratio ratio Mode 13h does not have completely square pixels.Mode

13 is something of a curiosity, because the VGA is from a hardware perspective a planar device, and so completely unsuited to chunky graphics. It was made possible by a ladbrokespoker.com hardware trick. In order to understand how Mode 13h was possible, one must consider the VGAs ladbrokespoker.com memory layout:The VGAs 256K of video ladbrokespoker.com memory is not directly available ladbrokespoker.com to the programmer and is accessed via a 64KB window in the PCs real mode address space. The Video RAM is actually a bank of 4 planes, 64KB each. By manipulating

the VGAs control registers ladbrokespoker.com the programmer can decide how some or all of these 4 planes will be affected by each write or read operation. In 256 colour mode each plane represents a pixel. For example, on the first line of the screen pixels 0, 4, 8, 12 etc. are all contained in memory plane 0, while pixels 1, 5, 9, 13 etc. are contained ladbrokespoker.com in memory plane 1 and so on. A single byte written to the 64K window therefore can address up to 4 pixels at once. The programmer through a combination of the

64K window available, and the selection of any of the four planes allows the manipulation of the total 256K video memory.Mode ladbrokespoker.com 13h though allows the programmer to access the VGA in the chunky fashion where every byte represents a single pixel. This is made possible because in Mode 13h the hardware uses the last two bits of the address to select the plane to write to. The upshot is that the programmer has a simple access model, the downside is that ladbrokespoker.com three quarters of the video memory is now inaccessible. A simple bank switching method could have made the remainingmemory available, and indeed bank switching was made available ladbrokespoker.com on Super VGAs to access the larger VRAMs these devices sported.Although never documented by IBM, ladbrokespoker.com ladbrokespoker.com an alternative planar 256 colour mode ladbrokespoker.com is available called Mode X.Computer graphics