完整的delphi程序设计教程课后习题答案

239页1题小时钟

procedure TForm1.Timer1Timer(Sender: TObject);

var

xt,yt:integer;

h,m,s,ms:word;

begin

decodetime(time,h,m,s,ms);

xt:=paintbox1.clientwidth div 2;

yt:=paintbox1.clientheight div 2;

paintbox1.refresh;

paintbox1.canvas.moveto(xt,yt);

paintbox1.canvas.pen.width:=3;

paintbox1.canvas.lineto(xt+round(sin((60*h+m)/(12*60)*2*pi)*100), yt-round(cos((60*h+m)/(12*60)*2*pi)*100));

paintbox1.canvas.moveto(xt,yt);

paintbox1.canvas.pen.width:=2;

paintbox1.canvas.lineto(xt+round(sin(m/60*2*pi)*140),

yt-round(cos(m/60*2*pi)*140));

paintbox1.canvas.moveto(xt,yt);

paintbox1.canvas.pen.width:=1;

paintbox1.canvas.lineto(xt+round(sin(s/60*2*pi)*180),

yt-round(cos(s/60*2*pi)*180));

end;

end.

239页3题求两点间的距离

procedure TForm1.Button1Click(Sender: TObject);

begin

paintbox1.Refresh;

formpaint(sender);

end;

procedure TForm1.FormPaint(Sender: TObject);

var

xt,yt:integer;

ax,ay,bx,by:integer;

begin

xt:=paintbox1.ClientWidth div 2;

yt:=paintbox1.Clientheight div 2;

paintbox1.canvas.MoveTo(xt,0);

paintbox1.canvas.lineTo(xt,2*yt);

paintbox1.canvas.MoveTo(0,yt);

paintbox1.canvas.lineTo(2*xt,yt);

ax:=strtoint(edit1.text);

ay:=strtoint(edit2.text);

bx:=strtoint(edit3.text);

by:=strtoint(edit4.text);

edit5.Text:=floattostr(sqrt((ax-bx)*(ax-bx)+(ay-by)*(ay-by))); paintbox1.canvas.MoveTo(xt+ax*10,yt-ay*10);

paintbox1.canvas.lineTo(xt+bx*10,yt-by*10);

end;

end.

226页5题输入学生成绩

var

Form1: TForm1;

type

studentrecord=record

xh,xm:string[6];

xb:boolean;

yy,sx,dz:integer;

end;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);

var t:studentrecord;

f:file of studentrecord;

size:integer;

begin

t.xh:=edit1.Text;

t.xm:=edit2.Text;

t.sx:=strtoint(edit3.Text);

t.yy:=strtoint(edit4.Text);

t.dz:=strtoint(edit5.Text);

if radiobutton1.Checked then

t.xb:=true

else

t.xb:=false;

assignfile(f,'c:\my documents\stu.dat');

if fileexists('c:\my documents\stu.dat') then

reset(f)

else

rewrite(f);

size:=filesize(f);

seek(f,size);

write(f,t);

closefile(f);

edit1.Text:='';

edit2.Text:='';

edit3.Text:='';

edit4.Text:='';

edit5.Text:='';

end;

procedure TForm1.Button2Click(Sender: TObject); begin

close;

end;

end.

226页8题保存获得奖学金者

var

Form1: TForm1;

type

studentrecord=record

xh,xm:string[6];

xb:boolean;

yy,sx,dz:integer;

end;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject); var t:studentrecord;

f,f1:file of studentrecord;

p1,p2:boolean;

begin

assignfile(f,'c:\my documents\stu.dat');

reset(f);

assignfile(f1,'c:\my documents\stu1.dat');

rewrite(f1);

while not eof(f) do

begin

read(f,t);

p1:=(t.sx>=85)and(t.yy>=85)and(t.dz>=85);

p2:=t.sx+t.yy+t.dz>=270;

if p1 or p2 then

write(f1,t);

end;

closefile(f);

closefile(f1);

end;

procedure TForm1.FormCreate(Sender: TObject);