*Cách có sử dụng chương trình con:

uses crt;

var st:string;

{--------------chuong-trinh-con---------------}

function doixau(st:string):string;

var i,d:integer;

begin

   d:=length(st);

   for i:=1 to d do

     st[i]:=upcase(st[i]);

   doixau:=st;

end;

{-------------chuong-trinh-chinh---------------}

begin

clrscr;

write('Nhap xau:'); readln(st);

writeln('Xau doi sang chu hoa la: ',doixau(st));

readln;

end.

*Cách không sử dụng chương trình con:

uses crt;

var st:string;

i,d:integer;

begin

clrscr;

write('Nhap xau:'); readln(st);

d:=length(st);

for i:=1 to d do 

 st[i]:=upcase(st[i]);

writeln('Xau sau khi doi la: ',st);

readln;

end.

Program HOC24;

var s: string;

i: byte;

begin

write('Nhap xau :'); readln(s);

for i:=1 to length(s) do if s[i]<>'a' then write(s[i]);

readln

end.

uses crt;

var st:string;

i,d:integer;

begin

clrscr;

write('Nhap xau:'); readln(st);

d:=length(st);

for i:=1 to d do 

 if st[i]='a' then delete(st,i,1);

writeln(st);

readln;

end.

uses crt;

var st:string;

begin

clrscr;

readln(st);

delete(st,3,5);

writeln(st);

readln;

end.

Program HOC24;

var s: string;

tg,d,max,i: byte;

code: integer;

begin

write('Nhap xau : '); readln(s);

// cau a

for i:=1 to length(s) do if s[i] in ['a'..'z'] then write(upcase(s[i]));

//------

writeln;

//-cau b

for i:=length(s) downto 1 do if s[i] in ['0'..'9'] then write(s[i]);

//------

writeln;

//---cau c

d:=0;

for i:= 1 to length(s) do

if s[i] in ['0'..'9'] then 

begin

val(s[i],tg,code);

if tg>max then max:=tg;

d:=d+1;

end;

if d=0 then write('Khong co chu so trong day') else write('Chu so lon nhat la : ',max);

readln 

end.

uses crt;

var st,st1:string;

d,i,d1,max,x,y:integer;

begin

clrscr;

write('Nhap xau:'); readln(st);

d:=length(st);

writeln('Day cac ki tu thuong doi sang chu hoa la: ');

for i:=1 to d do 

  if st[i] in ['a'..'z'] then write(upcase(st[i]):4);

st1:=''

for i:=1 to d do 

  if st[i] in ['0'..'9'] then st1:=st1+st[i];

d1:=length(st1);

for i:=d1 downto 1 do 

  write(st1[i]:4);

writeln;

max:=0;

for i:=1 to d1 do 

  begin

val(st1[i],x,y);

if max<x then max:=x;

end;

writeln('Chu so lon nhat trong xau la: ',max);

readln;

end.

Chương trình:program bai_10_chuong_4;uses crt;vars: string[100];i, dem: integer;Beginclrscr;write('Nhap xau vao:'); readln(s); dem:= 0;for i:= 1 to length(s) doif ('0'<=s[i]) and(s[i]<=’9') then dem:=dem+l;Writeln('Trong xau s co '»dem,' chu so thap phan');readln;End.

uses crt;

var st:string;

i,d:integer;

begin

clrscr;

write('Nhap xau:'); readln(st);

d:=length(st);

for i:=1 to d do 

  if st[i] in ['0'..'9'] then write(st[i]:4);

readln;

end.

uses crt;

var st:string;

d,i:integer;

begin

clrscr;

write('Nhap xau:'); readln(st);

d:=length(st);

for i:=1 to d do 

  if not(st[i] in ['a'..'z']) and not(st[i] in ['A'..'Z']) then write(st[i]);

readln;

end.