module
14
The Turbo course's S23 had ClrScr and GotoXY. HiSoft Pascal has neither - and needs neither, because the Einstein's screen understands a couple of control characters of its own, and WRITE can send them. With a three-line procedure you have GotoXY back.
PAGE clears the screen and puts the cursor at the top left - Turbo's ClrScr.
Write CHR(29), then a column, then a row, and the next thing written goes there:
WRITE(CHR(29),CHR(5),CHR(10),'A')
puts an A in column 5 of row 10. Note two things. The two numbers go in as characters, with CHR. And they count from 0: columns 0 to 39, rows 0 to 23, (0,0) the top left - where Turbo's GotoXY counted from 1. A number past the edge is ignored, and the cursor stays where it was.
CHR(30) on its own sends the cursor to the top left without clearing anything.
Wrap it in a procedure that takes Turbo's numbers, and your Turbo habits carry straight over:
PROCEDURE GOTOXY(X,Y:INTEGER);
BEGIN
WRITE(CHR(29),CHR(X-1),CHR(Y-1))
END;
GOTOXY(1,1) is the top left, GOTOXY(40,24) the bottom right. Do not write in that last cell: as in Turbo, it makes the whole screen scroll up a line.
TCOL(F,B) sets the colours of the text written after it: F for the letters, B for the background behind them, numbers from the manual's table of sixteen. Three useful ones:
TCOL | Gives |
|---|---|
TCOL(15,4) | White on blue - the screen's ordinary colours |
TCOL(15,6) | White on dark red |
TCOL(1,11) | Black on light yellow |
Set it back with TCOL(15,4) when you are done, or everything after - the 0: prompt included - carries on in your colours.
10 PROGRAM BOX;
20 VAR I:INTEGER;
30 PROCEDURE GOTOXY(X,Y:INTEGER);
40 BEGIN
50 WRITE(CHR(29),CHR(X-1),CHR(Y-1))
60 END;
70 BEGIN
80 PAGE;
90 WRITE('TOP LEFT');
100 FOR I:=10 TO 30 DO
110 BEGIN
120 GOTOXY(I,5); WRITE('#');
130 GOTOXY(I,15); WRITE('#')
140 END;
150 FOR I:=6 TO 14 DO
160 BEGIN
170 GOTOXY(10,I); WRITE('#');
180 GOTOXY(30,I); WRITE('#')
190 END;
200 TCOL(15,6);
210 GOTOXY(16,10); WRITE('EINSTEIN');
220 TCOL(15,4);
230 GOTOXY(1,20)
240 END.
Starting from
BOX.ASC saved from XBAS; HPEIN BOX.
What you should see
The screen clears; TOP LEFT in the corner; a box of # from column 10 to 30 and row 5 to 15; EINSTEIN in white on dark red in the middle of it; and the 0: prompt near the bottom, in the ordinary colours.
CHR(X-1) and CHR(Y-1). What happens to the box - and why does part of it go missing?0: prompt afterwards?GOTOXY(40,24); WRITE(CHR(42)). Where has the box gone?14.1 Write your name in the middle of an otherwise empty screen.
14.2 Count down from 5 to 1 in the same place on the screen, each number replacing the last, and then write GO. (A FOR loop of a few thousand empty passes makes a pause - S5.)
Worked solutions are in Appendix II.
| Symptom | Cause |
|---|---|
| Everything is one row down and one column right | The numbers after CHR(29) count from 0. Take one off Turbo's. |
| The drawing is turned on its side | Column and row the wrong way round: column first. |
| Part of a drawing is missing | A row past 23 or a column past 39 - it is ignored. |
| Everything has moved up | Something was written in the bottom-right cell. |
| The prompt is in odd colours after a program | It left TCOL set. End with TCOL(15,4). |
PAGE clears the screen. CHR(29), a column and a row - counting from 0 - move the cursor; CHR(30) sends it home. A three-line GOTOXY procedure gives you Turbo's version back. TCOL colours text; TCOL(15,4) puts it back.
S15, Keys Without ENTER - INCH, and why it needs (*$C-*).
