The Decision Control Structure

Question 1

Default Control Structure:

Answer 1

Sequence Control Structure.

Question 2

Decision control instruction is implemented using:

Answer 2

1. The if statement
2. if - else
3. Conditional Operators.

Question 3

if

Syntax:

Answer 3

if ( this condition is true)
execute this statement;

if (expression)
{
statement(s);
}

expression = 0 means false. non zero is true.

If { } is absent then immediately next statement after if is executed on satisfaction of expression.

Question 4

Decisions. In c?

Answer 4

When certain conditions are met we make decisions.
If they are not met, we don’t make that decision or don’t execute that statement.
Keyword if tells C that its time to make a decision.

Question 5

Relational Operators:

Answer 5

x == y            x is equal to y
  !=                      not equal
   <                    smaller than
     >                   greater than
< =  ,  > =

Question 6

What if a variable is not initialised:

Answer 6

Then it contains some unpredictable value, aka GARBAGE Value.

Question 7

Default Scope of If statement:

and else

Answer 7

Immediately next statement after it.

Question 8

The if - else statements:

Answer 8

else allows us to execute statments when condition is false.
if (Exp)
   {  Statement(s);  }
else
   { Statements(s); }

Question 9

Nested if-else:

Answer 9

adding if and else blocks within if or else blocks.

Question 10

Logical Operators:

Answer 10

&&= AND
|| = OR
! = NOT

Question 11

Use of logical operators:

Answer 11

Allows us to combine 2 or more conditions.

Question 12

else if Clause:

Answer 12

if()
{}
else if ()
{}
else
{}

last else is optional.

Question 13

Use of logical operators to optimize the code:

Answer 13

• If the ans boils down to 2 then. often called yes/No problem.
  if (exp1 || exp2.1 && exp2.2 || Exp 3 )
  {ans 1}
  else
  { ans 2 }
• To test if the value falls within a range or not.

Question 14

Precedence:

Answer 14

! 
> *,/,% > +,- 
 >  
'', '>=', '<=',  
> ==, != 
> &amp;&amp; 
>|| 
> =

Question 15

What if you add semicolon at the end of if’s condition
if ();
{ if block }

Answer 15

Then if condition satisfied a null statement will get executed which does ntg, if not satisfied then it won’t get executed. either ways the if block will get executed.
if ()
;
{ if block }

Question 16

if( i = 5)
printf (‘true’);
output?

Answer 16

You will always get true as ans cuz its basically
if (5)
printf(‘true’);
as assignment operator is used and not ==.

Question 17

The Conditional Operators:

Answer 17

aka ternary operators, take 3 arguments.

expression 1 ? expression 2 : Exp 3

if-then-else.

Ex:
y = (x>5?3:4);
printf(“%c”, (a >=’a’ ? a : ‘!’) ); [execute this, testing should be declared before or add quotes.]
They can be nested as well.

Question 18

Lvalue Required

Error:

Answer 18

a > b ? g = a : g = b;
will give that error.
a > b ? g = a : (g = b);

In absence of parentheses, the compiler believes that b is being assigned to result of the expression to the left of 2nd =. Hence it reports an error.

Works fine

int main()
{
    int a,b,g;
    a = 5; b = 10; g = 0;
    a > b ? g = a : (g = b);
    printf("%d",g);

return 0; }

Question 19

limitation of ? :

Answer 19

: after this only one statement alowed…