A display system for displaying characters on a screen which is divided into a plurality of display areas and for allowing a scroll within each of the display areas with one chip of display data RAM without image confusion between the display area. The display data RAM is also divided into plural areas corresponding to the display areas. This system includes address conversion circuit provided between a display controller and the display data RAM for converting a virtual address outputted from the display controller into an actual address of the display data RAM. Here the virtual address is an address out of actual address of the display data RAM.

There is provided a video display controller which can vertically and horizontally shift a whole video image displayed on a screen of a video display unit. The video display controller comprises an image data read circuit which reads the image data from a video RAM, a register into which data representative of amount of shift of the video image is stored by a central processing unit, and a first counter which cyclicly counts a clock signal. An adder adds the data contained in the register and a count output of the first counter, and at a timing determined by this addition result a predetermined value is preset into a second counter. This second counter counts the clock signal from the predetermined value, and the image data read by the image data read circuit is outputted to the video display unit at a timing in accordance with a count output of this second counter. The register, first counter, adder and second counter are provided in each of vertical and horizontal scanning control circuits.

In a CRTC scan circuit, a waste of memory space used in a character generator, such as a conventional Chinese character generator, during the scan can occur, thus an address conversion for a character generator is provided so that the memory space is completely utilized. The procedure of address conversion is carried out by dividing the MASKROM memory space which is used in a character generator into two separate pluralities of partition groups according to a "character frame space" and an "actually used space" of a character, establishing an address mapping between those two partition groups, and determining an offset value between the input and output address data in this mapping. A general rule about the relation between these two partition groups is given and an address converter to perform the procedure is disclosed.

Disclosed is encoded data representing knots on an outline defined relative to a coordinate plane involving selecting sets of coordinates on said outline, to represent said knots, establishing a successive order of said knots, encoding said knots in a data order indicative of said knot order, and encoding by encoding a complete information set of data providing a control code indicative of either (i) the coordinate locations of said knots or (ii) a knot's direction relative to others of said knots or (iii) a predetermined shape of said outline between a pair of said knots or (iv) data indicative of the shape of said outline at a knot or (v) encoding a complete information set providing the coordinate distances between adjacent knots.

Disclosed is encoded data representing knots on an outline defined relative to a coordinate plane and decoded for use in a display process to produce images of said outlines represented by said encoded data involving selecting sets of coordinates on said outline, to represent said knots, establishing a successive order of said knots, encoding said knots in a data order indicative of said knot order, by encoding a complete information set of data providing a control code indicative of either (i) the coordinate locations of said knots or (ii) a knot's direction relative to others of said knots or (iii) a predetermined shape of said outline between a pair of said knots or (iv) data indicative of the shape of said outline at a knot, or (v) providing data indicative of the coordinate distances between adjacent knots decoding said complete information sets in a decoding order related to said data order, responsive to said complete information set being indicative of the coordinate distances between adjacent knots, producing an image of a smooth continuous curved outline or a straight line between said adjacent knots or, responsive to said complete information sets being indicative of a control code as set forth in (i), (ii), (iii), or (iv), producing an image of a smooth continuous outline or a straight line according to the said coordinate locations of said knots relative to adjacent knots in said successive knot order or producing an image of said outline being smooth at respective knots or being sharp and forming cusps at respective knots.