>>Don't forget that 0,0 is at the top left & the x-axis increases down the screen. This makes a positive slope go from upper left to lower right. So in terms of "upwards slope" relating to to a mathematically positive slope then VfP is wrong & VB is right. In purely visual terms, I agree with you, that upwards is the otherway round. It's a poor choice of words for the documentation.
>
>Len, are we having a cultural difference here?

No - my mistake - I didn't notice that I'd written x instead of y.

>
>In all my math classes, the X axis was horizontal and the Y axis was vertical. (0,0) was always somewhere on the lower left. Is the "usual" picture different in the UK?
>

>Y Axis
>|   /
>|  / <<- Positive slope
>| /
>|/_______________ X Axis
>(0,0)

That is the usual representation of the axes & a positive slope (which I would also call an upward diagonal). But in many computer graphics systems, including VFP, VB, VC++, 0,0 is situated at the top left & the positive direction for y is downwards. In the majority of graphics libraries I have used over the years, I can only remember one occassion where I didn't write my own front-end library of routines to put the origin back to the bottom right so I could use a natural coordinate system.

I think this is where the confusion may have come from - upward diagonal has been used in the mathematical sense of increasing y value with increasing x value (hence top left to bottom right) rather than the normally accepted sense of your image.

I'm still pondering in which direction I would expect an upward diagonal to go as I traverse the negative side of the x-axis - does it go upwards or downwards. In other words is an upward diagonal one where the y value increases with distance from the origin.

                Y Axis
 Upward ->>\   |
 Diagonal ? \  |
             \ |
______________\|
X Axis -ve side(0,0)

"Upward" is a relative term depending on direction of travel, a valley consists of a negative slope followed by a positive slope (left to right), but from the bottom which ever direction you travel you always go upwards.