Abstract: A method of establishing a clock for the UART circuit provided in a standard I/O card or a combined graphic and I/O card is disclosed. The essential step of the method of the invention is to directly impress the clock of the main board of a personal computer into the UART circuit of the I/O card thereby eliminating the need for an independent crystal for the UART circuit. In an alternative embodiment of the method according to the present invention, the clock for the graphic data processing circuit provided in a combined graphic and I/O card is impressed directly to the UART circuit provided in the same card. The method of establishing a clock in the I/O card also includes a step of processing the directly impressed clock, either from the main board of the personal computer or from the graphic data processing circuit, to obtain the desired clock for the UART circuit with a desired frequency.

Abstract: A highly efficient method of line drawing on a raster scan display device. By properly shifting the original coordinates, a line can be represented by an equation such as X=(Q+r/.DELTA.Y)Y if the slope (.DELTA.Y/.DELTA.X) is between 0 and 1. Q and r are the integer quotient and remainder, respectively, when .DELTA.X is divided by .DELTA.Y. An error term D and a MODIFIER term are determined in accordance with the proposed algorithm for each value of Y. The final line is formed when the positions of (.DELTA.Y+1) line segments, with different numbers of horizontal points in each line segment, are determined. By this technique, when the quotient Q is odd, the number of points to be drawn for the first line segment are (Q+1)/2 and the points of the rest of the line segments are Q+MODIFIER. When the quotient Q is even, the points of the first line segment are Q/2 when r=0, or (Q/2)+1 when r not equal to 0. The points of the remaining line segments are Q+MODIFIER.