{Character.ToUpper}字符串转换成大写
procedure TForm1.Button1Click(Sender: TObject);
var
c: Char;
str: string;
begin
c := ToUpper('a');
str := ToUpper('Delphi');
ShowMessageFmt('%s, %s', [c, str]); {A, DELPHI}
end;

{Character.ToLower}字符串转换成小写
procedure TForm1.Button2Click(Sender: TObject);
var
c: Char;
str: string;
begin
c := ToLower('A');
str := ToLower('Delphi');
ShowMessageFmt('%s, %s', [c, str]); {a, delphi}
end;

IsLetter: {是否是个字母; 范围 A..Z 与 a..z}
IsUpper: {是否是个大写字母; 范围 A..Z}
IsLower: {是否是个小写字母; 范围 a..z}
IsDigit: {是否是个十进制数字; 范围 0..9}
IsNumber: {是否是个数字符号; 范围包括 0..9, 还有 ASCII 码中的 178、179、185、188、189、190 等}

{IsLetter: 是否是个字母}
procedure TForm1.Button1Click(Sender: TObject);
var
b1,b2,b3: Boolean;
begin
b1 := IsLetter('A'); {是}
b2 := IsLetter('a'); {是}
b3 := IsLetter('9'); {否}
ShowMessageFmt('%s,%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True),BoolToStr(b3,True)]);
{True,True,False}

b1 := IsLetter('D2009', 1);
b2 := IsLetter('D2009', 2);
ShowMessageFmt('%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True)]);
{True,False}
end;

{IsUpper: 是否是个大写字母}
procedure TForm1.Button2Click(Sender: TObject);
var
b1,b2,b3: Boolean;
begin
b1 := IsUpper('A'); {是}
b2 := IsUpper('a'); {否}
b3 := IsUpper('9'); {否}
ShowMessageFmt('%s,%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True),BoolToStr(b3,True)]);
{True,False,False}

b1 := IsUpper('Delphi', 1);
b2 := IsUpper('Delphi', 2);
ShowMessageFmt('%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True)]);
{True,False}
end;

{IsLower: 是否是个小写字母}
procedure TForm1.Button3Click(Sender: TObject);
var
b1,b2,b3: Boolean;
begin
b1 := IsLower('A'); {否}
b2 := IsLower('a'); {是}
b3 := IsLower('9'); {否}
ShowMessageFmt('%s,%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True),BoolToStr(b3,True)]);
{False,True,False}

b1 := IsLower('Delphi', 1);
b2 := IsLower('Delphi', 2);
ShowMessageFmt('%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True)]);
{False,True}
end;

{IsDigit: 是否是个十进制数字}
procedure TForm1.Button4Click(Sender: TObject);
var
b1,b2,b3: Boolean;
begin
b1 := IsDigit('A'); {否}
b2 := IsDigit('½'); {否}
b3 := IsDigit('9'); {是}
ShowMessageFmt('%s,%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True),BoolToStr(b3,True)]);
{False,False,True}

b1 := IsDigit('D2009', 1);
b2 := IsDigit('D2009', 2);
ShowMessageFmt('%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True)]);
{False,True}
end;

{IsNumber: 是否是个数字符号}
procedure TForm1.Button5Click(Sender: TObject);
var
b1,b2,b3: Boolean;
begin
b1 := IsNumber('A'); {是}
b2 := IsNumber('½'); {是}
b3 := IsNumber('9'); {否}
ShowMessageFmt('%s,%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True),BoolToStr(b3,True)]);
{False,True,True}

b1 := IsNumber('123¹²³¼½¾', 1);
b2 := IsNumber('123¹²³¼½¾', 4); {这里的 9 个字符全都复合}
ShowMessageFmt('%s,%s', [BoolToStr(b1,True),BoolToStr(b2,True)]);
{True,True}
end;