DiagScan -Basic Algorithm:

             Space Object                      sp;      // Space object to be scanned

             integer                          dirdir;               // direction of diagonal scan (left or right)
             integer                        dirfase;              // phase of scan (up or down)
             integer                     edgefase;    // direction of scan (clockwise or anti-clockwise along edges)
             integer          diractive;              // diagonal movement or edge-step active at moment
             integer                          curdir;             // current coded direction
           integer                           zigsw;            // determines mode of scan (zigzag or zig)

             integer             initflag;    // initial coded flag value (starting position)
             integer                        endflag;       // end coded flag value (opposite corner)
             integer             eos;    // flag signifying end of space (when in "scan" mode)

             integer array (1-D)    tempos;    // stored (temporary) position at begin of zig (for zig only)
             integer array (1-D)        flags;           // signals identifying position in parameter range
             integer        flagcode; // flag coded to identify edges and corners (see diagramme)

             integer array (2-D)    dirtable;       // converts code to direction increments
             integer array (2-D)    stepcode = {{3,6},{6,3},{2,1},{2,6},{6,1},{1,2},{3,2},{1,3}}; // sets step direction (along edge)
             integer array (2-D)       dircode = {{7,5},{8,4}};    // coded diagonal directions

                                 Set <dirdir> (direction of diagonal, / or \)
                                 Set <dirfase> (phase of diagonal -zig or zag)
                                   Get <curdir> from <stepcode> table (flagcode-1, edgefase)
                                                             Convert <curdir> into directional increments for Space Object
                         Store current (X,Y) position in <tempos>
                                                                                             Set <diractive> flag to <1> (simulating a diagonal movement)

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                            Main Process
                           Set End of Scan flag to <0> (scan not yet ended)
                                       Depending on <zigsw> follow Zig Process or ZigZag Process
                                         Increment (X,Y) position of Space Object

                                                                  Zig Process
                   IF (X,Y) position at an edge or corner (flagcode != 0) THEN

                                                              Make edge step Move
                                                                                                             Set (X,Y) position to <tempos>
                   Increment Space Object to new edge position
                         Store current (X,Y) position in <tempos>

                                                                                                       Prepare diagonal move
                                    Get <curdir> from <dircode> table (dirdir, dirfase)
                                                              Convert <curdir> into directional increments for Space Object
                                                                                            Set <diractive> flag to <1> (signaling a diagonal movement)

ZigZag Process
               IF (X,Y) position at an edge or corner (flagcode != 0) THEN
                                                                                                 IF just made diagonal movement (diractive = 1) THEN
                                                                                                           Prepare Edge step
                                   Get <curdir> from <stepcode> table (flagcode-1, edgefase)
                                                                   Convert <curdir> into directional increments for Space Object
                                                                                                                   Reverse phase of <edgefase > (edgefase = 1 -edgefase)
                                                                                                     Set <diractive> flag to <0> (signaling a step movement)
                                                                                 IF just made step movement (diractive = 0) THEN
                                                                                                            Prepare Diagonal movement
                                    Get <curdir> from <dircode> table (dirdir, dirfase)
                                                              Convert <curdir> into directional increments for Space Object
                                                                                            Set <diractive> flag to <1> (signaling a diagonal movement)

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DiagScan -Basic Algorithm:

Variable List:

Basic Algorithm: