Program PR1C1DT;

uses
    Graph, CRT, CALCUNIT;
var
    ga, gm, error : integer;
    X, Y, e, step : real;
    A, MX, MX05, MY, MY05, MY005, MSY, MSX : integer;
    ST : string[4];
begin
    ga := detect;
    gm := detect;
    initgraph(ga, gm, '');
    error := graphresult;
    if(error <> grok) then begin
        writeln('ERROR GRAPHICS INIT', #10#13, grapherrormsg(error));
        halt;
    end;
    MX := GetMaxX;
    MY := GetMaxY;
    MX05 := round(0.5 * MX);
    MY05 := round(0.5 * MY);
    MY005 := round(0.05 * MY);
    setColor(14);

    Line(5, MY05, MX-10, MY05);
    Line(MX05, MY005, MX05, MY-9);
    Line(MX-10, MY05, MX-20, MY05+3);
    Line(MX-10, MY05, MX-20, MY05-3);
    Line(MX05, MY005, MX05+3, MY005+10);
    Line(MX05, MY005, MX05-3, MY005+10);

    SetTextStyle(0, 0, 1);
    SetColor(14);
    OutTextXY(MX05 - 40, MY005, ' Y ');
    OutTextXY(MX-40, MY05-40, ' X ');

    MSY := 30 + round(MY/3);
    Y := -1;
    while(Y <= 1) do begin
        str(Y : 4 : 1, st);
        A := round(MY05 - MSY * Y);
        Line(MX05 + 3, A, MX05 - 3, A);
        OutTextXY(MX05 - 40, A - 3, ST);
        Y := Y + 0.1;
    end;
    MSX := round(MX/3);
    X := -1;
    while(X <= 1) do begin
        STR(X : 4 : 1, ST);
        A := round(MX05 + MSX * X);
        Line(A, MY05 + 3, A, MY05 - 3);
        OutTextXY(A, MY05 + 15, ST);
        X := X + 0.1;
    end;
//////////////////////
    e := 1E-3;
    x := -0.9;
    step := 0.001;
    while(X <= 0.9) do begin
        Y := WRF(x, e);
        PutPixel(round(MX05 + MSX * X), round(MY05 - MSY * Y), 2);
        X := X + step;
    end;
    OutTextXY(5, 5, 'Y = arctg(x)');
//////////////////////
    readln();
    closeGraph;
end.