Question

c programming

1. Explain the difference between the statements on the left and the statements on the right for each group of statements, give the final value of x if the initial value of x is 1

If (x>=0) x =x +1; Else if (x>=1) x = x+2;

If ( x>=0) x = x+1; if (x>= 1) x=x+2;

Answer 1

# Answer :

GIven : x = 1

Statements on the Left :

If (x>=0)
x =x +1;
else if (x>=1)
x = x+2;

Evaluation : x>=0 1>=0 true . So the first If statement is true . Therefore x =x +1 x =1+1 x = 2 . All other conditions are skipped.

Final Result : x = 2

Explanation :

• This is if-elseif ladder. Here if the specified condition is not true, it will continue to check the next condition in the ladder (next else if) until it satisfies any condition.
• The format of the if else if ladder is :

if(condition 1){
   // if condition 1 is true execute this block
}
else if(condition 2){
   // if condition 1 is false and condition 2 is true execute this block
}
else if(condition 3){
   // if condition 1 is false, condition 2 is false and condition 3 is true execute this block
}
else{
   // if all the conditions are false then execute this block (optional block)
}

• Here, it will continue to check the next condition in the ladder (next else if) until it satisfies any condition.
• else is an optional block, it executes when none of the conditions are true.
• Once it finds the first condition which it satisfies, it executes its block and skips all the other conditions after it in the else ladder even if they are satisfied.
• In the above, the problem both the conditions satisfy the given value of x, but only the first one which comes in the ladder is being executed and others which are after it are skipped.
• Hence, if(x>=0) condition block is only executed because it is the earliest condition block.

Statements on the Right :

If ( x>=0)
x = x+1;
if (x>= 1)
x=x+2;

Evaluation :

The first condition : x>=0 1>=0 true . Therefore, x = x+1 x = 1+1 x = 2.

The value of x is now 2. (x =2)

The second condition : x>= 1 2>=1 true . Therefore, x = x+2 x = 2+2 x = 4

The value of x is now 4. (x =4)

Final Result : x = 4

Explanation :

• There are two separate simple if statements.
• The format of simple if  :

if(condition){
   // if condition is true this block will be executed otherwise skipped
}

• Above problem (Statements on the right) both the if statements will be executed as they are separate.
• FIrstly If ( x>=0) is executed which will update the value of x if the condition is true. It evaluates true and sets value of x to 2 (x = 2).
• Secondly If ( x>=1) is executed which will update the value of x if the condition is true. It evaluates true and sets value of x to 4 (x = 4).
• So the final value of x here is 4.

Difference between the Left and Right Statements :

• Left statements form an if-elseif ladder. Here the first condition which satisfies is executed and other conditions are skipped even though they are satisfied.
• While the right statements have two separate if statements. They are executed one by one updating the value of x.