1-if_then_else,
thats means if (condition=true)/OR (condition=true)/And
(Condition=true) then (do something)
else (condition between if then=wrong)
(do something)
compond statement is provided for this
work.
sample 1:
program IFTHENELSE;
const
{const is used to put a number or string to a variable}
a=1;
b=2;
begin
if (a>b) then
writeln('A is greater then
B') {semi colon are not allowed in
this time}
else
('B is greater then A');
{and simply ,else can be removed}
end.
sample 2:
program IFTHENELSE2;
const
{const is used to put a number or string to a variable}
a=1;
b=2;
c=3;
begin
if (a>b) then
begin
if (a>c) then
writeln('A
is the greatest')
else if (c>a)
then
writeln('C
is the greatest')
end;
else
begin
if (c>b)
then
writeln('C is the greatest')
else
writeln('B is the greatest')
end;
end.
sample 3:to show use of not ,>=,<= ,and ,or
program notS;
const
a=1;
b=2;
begin
if (a=b) then writeln('a is equal to
b');
if (a>b) or (a=b) then writeln('a is
greater then or equal to b');
{ the above statement can be shorten
to IF (a>=b) then ('.....');}
if (a<b) and (a=b) then writeln('A
is smaller then and equal to b');
{the above line have error,A number
can't smaller then and equal to other number}
if (a=b) and (b=2) then writeln('A equal
to B and equal to 2');
if Not(a=b) then writeln('A is not equal
to B');
{the above line can be replace
by if (A<>B) then writeln('.....');
this NOT(a=b) method is always
used in C language}
end.
2.case of
some time if then statement is too long to
the condition!!
so case_of statement is deleveloped like a
switcher,
which equal to the swith statement of C;
sample 4:
program CASEOF;
var
a:integer;
begin
write('put number here:(1-4)');
readln(a);
case a of
1:writeln('a=1')
2,3:writeln('a=2 or a=3');
4:writeln('a=4');
end; {end are required for
case statement}
end.
{we use if then statement to compare}
if a=1 then
writeln('a=1');
if (a=2) or (a=3) then
writeln('a=2 or a=3')
else
writeln('a=4');
{which is longer then case statement!!}