for Loop in C

There may be a situation, when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.
Programming languages provide various control structures that allow for more complicated execution paths.
A For loop statement allows us to execute a statement or group of statements multiple times and following is the general form of a For loop statement :

Synatax:

for(initial expression; test expression; update expression) 
{ 
body of loop; 
}

Lets take an Simple Example:

#include<stdio.h>
int main()
{
        int i;
        for(i=0;i<=5;i++)
              printf("Hello World");
         return 0;
}

Output:
it will print five times Hello World

Explanation of For Loop :

1.Firstly the for loop executes the initialize statement in which the subscript variable will be initialized
with the initial value.

2.After the initialize statement the condition part of the loop will be executed if the condition becomes true then body of the loop will be executed otherwise the loop will be terminated

3.If the loop condition becomes true then body of the loop will be executed. After the execution of the for loop body the control goes to the third part of the loop statement i.e Expression Updation

4.After updating subscript variable control again goes to execute condition statement.

for more understanding the flow of loop plz go here....


Different ways of using For loop :

In order to do certain actions multiple times , we use loop control statements. For loop can be implemented in different verities of using for loop -

1. Single Statement inside For Loop
2. Multiple Statements inside For Loop
3.  No Statement inside For Loop
4.  Semicolon at the end of For Loop
5.  Multiple Initialization Statement  inside For Loop
6.  Missing Initialization in For Loop
7.  Missing Increment /Decrement  Statement
8.  Infinite For Loop
9.  Condition with no Conditional Operator.

Way 1 : Single Statement inside For Loop

for(i=0;i<5;i++)
     printf("Hello");

1. Above code snippet will print Hello word 5 times.
2. We have single statement inside for loop body.
3. No need to wrap printf inside opening and closing curly block.
4. Curly Block is Optional.

Way 2 : Multiple Statements inside For Loop

for(i=0;i<5;i++) 
{ 
        printf("Statement 1"); 
        printf("Statement 2"); 
        printf("Statement 3"); 
        if(condition)     
        {     
              --------     
              --------     
          } 
  }

If we have block of code that is to be executed multiple times then we can use curly braces to wrap multiple statement in for loop.

Way 3 : No Statement inside For Loop

for(i=0;i<5;i++) 
{   }

1.This is bodyless for loop. It is used to increment value of “i”.
2.This verity of for loop is not used generally.
3.At the end of above for loop value of i will be 5


Way 4 : Semicolon at the end of For Loop

for(i=0;i<5;i++);

1. Generally beginners thought that , we will get compile error if we write semicolon at the end of for loop.
2. This is perfectly legal statement in C Programming.
 3. This statement is similar to bodyless for loop. (Way 3)

Way 5 : Multiple Initialization Statement inside For

for(i=0,j=0;i<5;i++) 
{ 
       statement1; 
       statement2;  
       statement3; 

}

Multiple initialization statements must be seperated by Comma in for loop.


Way 6 : Missing Increment/Decrement Statement

for(i=0;i<5;) 
{ 
        statement1; 
        statement2; 
        statement3; 
         i++; 
}

however we have to explicitly alter the value i in the loop body.

Way 7 : Missing Initialization in For Loop

i = 0;
for(;i<5;i++) 
{ 
       statement1; 
       statement2;
       statement3;
 }

we have to set value of ‘i’ before entering in the loop otherwise it will take garbage value of ‘i’.

Way 8 : Infinite For Loop

i = 0;
for(;;) 
{ 
       statement1; 
       statement2; 
       statement3; 
       if(breaking condition)    
              break; 
        i++; 
}

Infinite for loop must have breaking condition in order to break for loop. otherwise it will cause overflow of stack.

Read More

Do-While In Java

Do-While Loop

The do-while loop always executes its body at least once,because its conditional expression is at the bottom of the loop.It repeats the statement or block of code while its controlling expression is true.It can execute the statements at least one  or more times.

Syntax of the while loop:

do
{
   //statements
}while(condition);

Each iteration of the do-while loop first execute the body of the loop and then evaluates the conditional expression.If this expression is true, then loop will repeat otherwise the loop terminates.

Flow Chart Of do-while loop:

Simple program of the while loop:

package org.modi;
public class Test
{
    public static void main(String[] args)
    {
 int i=5;
 do
 {
  System.out.println("Count " + i );
  i--;
 }while(i>0)
   }
}

OUTPUT

Count 5
Count 4
Count 3
Count 2 
Count 1

Read More

While in Java

While Loop

The while loop is Java's most fundamental loop statement.It repeats the statement or block of code while its controlling expression is true.In while loop, condition is given before the statement.  It can execute the statements 0 or more times.

Syntax of the while loop:

while(condition)
{
   //statements
}

The condition can be any boolean expression.The body of the loop will be executed as long as the conditional expression is true.

When condition becomes false , control passes to the next line of code immediately following the loop.

If loop have only one statement then , curly braces are not necessary.

Flow Chart of the while loop:

Simple program of the while loop:

public class Test
{
 public static void main(String[] args)
 {
  int i=5;
  while(i>0)
  {
   System.out.println("Count " + i );
   i--;
  }
 }
}

OUTPUT

Count 5
Count 4
Count 3
Count 2
Count 1

Some important points about while loop:

1.Since the while loop evaluates its conditional expression at the beginning the loop , the body of the loop        will not execute if condition is false at the beginning.

public class Test
{
 public static void main(String[] args)
 {
  int i=5 , j=10;
  while(i>j)
  {
   System.out.println("While loop body");
  }
  System.out.println("Out of While loop");
 }
}

OUTPUT

Out of While loop

2. The body of the while loop can be empty.This is because a null statement is syntactically valid in java.

public class Test
{
 public static void main(String[] args)
 {
  int i=5 , j=10;
  while(++i<--j)
  System.out.println(i);
 }
}

OUTPUT

8

3.If condition will always true then it will become infinite loop.

while(true) //infinite loop

Read More

Decision Making In C

Decision making is about deciding the order of execution of statements based on certain conditions or repeat a group of statements until certain specified conditions are met. C language handles decision-making by supporting the following statements,

• if and else statement
• for loop
• do-while loop
• break and continue
• switch-case statement
• goto statement

This also we known as control statement.It is also divided into following category:
1. Selection statements.(if..else and switch-case statement)
2. Iteration or looping statements.(for loop and do-while loop)
3. Jump statements.(break, continue and goto statement)

Read More