Difference between Decimal BASIC and Microsoft BASIC
A coordinate system is introduced by a SET WINDOW statement.
SET WINDOW has four parameters left, right, bottom, top.
That is, first two parameters are the range of x-coordinate, the rest are the range of y-coordinate.
SET WINDOW x1,x2,y1,y2
correspond to WINDOW (x1,y2)-(x2,y1) on Quick BASIC.
The positive direction of y-axis is upward, though a user can set the coordinate system y-axis downward.
can be replaced by
SET WINDOW x1,x2,y2,y1
If you want to set the pane size 640×480, execute an original statement
SET BITMAP SIZE 640,480
2. Points and lines
In most cases, re-written can be done by
LINE (x1,y1)-(x2,y2) by
PLOT x1,y1 ; x2,y2
LINE -(x,y) by
PLOT x,y; means
LINE (x,y)- in the notation style of Microsoft BASIC.
The PLOT x,y; executed first does not draw a line except the point.
That is, the PLOT x,y; executed first determines the initial point of a line graph.
To terminate a line graph, add a PLOT statement that has no arguments.
Refer to Introduction to BASIC Curves and Graphs
Foundation of Graphics