The 'CLEAR' mnemonic is used to initialize the plotting viewport. On a plotting display, the integer argument may be used as the color to initialize the plotting area. On a plotting printer, the current plot may be printed and the printer advanced to the next page (if possible). On a vector plotter, PRO/5 will attempt to give the operator some indication of completion (requesting a new page to be loaded). The indication will typically be in the form of a 'beep' or some other attention getting device. Some devices will not begin output of a plot until you send a 'CLEAR'(-1).
Absolute vs. Relative Mode
The 'ABS' mnemonic places the plot driver into a mode where the X and Y values are considered absolute values. The 'REL' mnemonic places the plot driver into a mode where all received X and Y values are added to the current position (set by most any mnemonic that isn't setting a mode). In a case where the plot driver is accepting multiple points, the new X and Y values used for the relative mode are not set until the completion of the actual plotting. Neither the 'ABS' or 'REL' mnemonics accept any arguments.
The 'MOVE' and 'DRAW' mnemonics are used in the simplest case for line plotting. The 'MOVE'(x,y) mnemonic places the plotter cursor to the specified x and y coordinates without drawing a line. From that point, a line may be drawn to a new pair of coordinates via the 'DRAW'(x,y) mnemonic. The cursor is left at the coordinate pair defined by the 'DRAW' mnemonic.
A single line may be placed using the 'LINE' mnemonic. The 'LINE'(x0,y0,x1,y1) will draw a line between the specified coordinate pairs. The cursor is left at the x1,y1 coordinates. All lines are drawn using the current style and color.