The document discusses different control statements in C including if, switch, and goto statements. It describes the basic syntax and usage of simple if statements, if/else statements, nested if/else statements, else if ladders, and switch statements. Key details include that if statements control program flow based on conditions, switch statements allow multi-way decisions by comparing an expression to case values, and break statements in switch cases determine where control transfers after each block.

1. Control statements
Topics
 if statement
 switch statement
 goto statement

2. If statement
 The if statement is a powerful decision
making statement and is used to control the
flow of execution of statements.
 The if statement can be implemented in
different forms:
1. Simple if statement
2. if….else statement
3. Nested if….else statement
4. else if ladder

3. Simple If statement
 The general form of a simple if statement is:
if(condition)
{
statement-block;
}
satement-x;
 If the condition is true then statement-block
is executed; otherwise the statement-block
will be skipped and the execution will jump
to the statement-x;

4. If…else statement
 The if…else statement is an extension of the
simple if statement. The general form is
if(condition)
{
True-block statement(s)
}
else
{
False-block statement(s)
}
statement-x;

5. Continue..
 If the condition is true then the true-block
statement(s) will execute; otherwise the
false-block statement(s) will execute.
 Then it will go to statement-x
 Ex: if(x>y)
z=x-y;
else
z=y-x;
printf(“%d”,z);

6. Nested If…else statement
 When a series of decisions are involved, we may have to use more than one
if…else statement in nested form as follows:
if(condition-1)
{
if(condition-2)
{
statement-1;
}
else
{
statement-2;
}
}
else
{
statement-3;
}
statement-x;

7. Continue…
 If condition-1 is false then statement-3 will
be executed; otherwise if continues to
perform the second test.
 If the condition-2 is true, then statement-1
will be executed; otherwise statement-2 will
be executed.
 Then the control will be transferred to
statement-x.

8. Else If ladder
 There is another way of putting ifs together when
multipath decisions are involved. The general
form:
if(condition-1)
statement-1;
else if(condition-2)
statement-2;
-------------
else if(condition-n)
statement-n;
else
default-statement;
statement-x;

9. Continue..
 The conditions are evaluated from the top.
As soon as a true condition is found, the
statement associated with it is executed and
the control is transferred to the statement-x.
 When all the conditions are false then the
final else containing the default-statement
will be executed.

10. switch statement
 Switch is a multiway decision statement. The
general form:
switch(expression)
{
case value-1: block-1;
break;
case value-2: block-2;
break;
-------------
default: default-block;
}
statement-x;

11. Continue…
 The expression is an integer expression or
character. Value-1, value-2,… are constants or
constant expression and are known as case
labels. Each of these values should be unique.
 When the switch is executed, the value of the
expression is successively compared against the
values value-1, value-2,….If a case is found whose
value matches with the value of the expression,
the block of statements are executed.
 The break at the end of each block signals the end
of particular case and causes exit from switch and
transfer control to statement-x.
 The default is optional and if no matches occur
then this default-block is executed.