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Infinite loop in C

Definition of infinite loop

The infinite loop is a loop that does not get dismissed because of its looping construct. A continuous output or no output are the two possible outcomes of this loop. It is also known as an endless loop or an indefinite loop.

There are a lot of applications where an infinite loop is helpful in running applications continuously. Those applications also produce endless outputs until the process is terminated manually. A few of them are the following:

  • Games: The user can play unlimited matches continuously, but if the user wants to stop the match, the h/.she has to exit the game manually. The game does not terminate on its own.
  • Operating Systems: As we usually observe, any operating system does not terminate its functioning on its own after the completion of the task until and unless the user manually shuts down the system.
  • Servers and website: Infinite loop is also used in servers and websites, which produce the continuous output as the user asks to carry out the process. This processing only gets dismissed when the user closes the website or when the administrator manually shuts the servers and websites down.

Now we will see how to initiate the infinite loop in various looping codes:

For loop

The statement for the infinite for loop is mentioned in the following block:

for(; ;)  // initiating "Infinite For Loop".
{  
    // main body of the "Infinite For Loop".  
}

In the above program line, no condition is mentioned so that it can produce infinite outcomes.

Now, it’s time to know precisely about this with the help of an example.

#include <stdio.h> // basic program line
int main()  
{  
    // initialising without any condition 
   for(;;)  
   {   
     printf("Hello, world!!!\t"); // main program line 
   }  
return 0;  
} 

Output:

Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!!
Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!!
Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!!
Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!!
Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!!
Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!! 
Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!!
Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!!
Hello, world!!! Hello, world!!! Hello, world!!! Hello, world!!!

While loop

// here, 1 represents the condition as true 
while(1) 
{  
   // main body of the "infinite while loop".  
}  

Example of Infinite while loop:

// basic program lines 
#include <stdio.h>  
int main()  
{  
  int a=1; // initialising the value of a as 1
  while(1)
  {  
      a++;   // increment or decrement statement 
      printf("now a is:%d \t",a);  
  }  
return 0;  
}  

Output:

188     now a is:125189        now a is:125190        now a is:125191    now a is:125192         now a is:125193        now a is:125194        now a is:125195     now a is:125196        now a is:125197        now a is:125198        now a is:125199     now a is:125200        now a is:125201        now a is:125202    now a is:125203         now a is:125204        now a is:125205        now a is:125206     now a is:125207        now a is:125208        now a is:125209        now a is:125210     now a is:125211        now a is:125212        now a is:125213    now a is:125214         now a is:125215        now a is:125216        now a is:125217     now a is :

Do-while loop

do  
{  
    // main body of the infinite do-while loop.  
}
while(1);  

Example of Infinite Do-while loop:

#include <stdio.h> // basic program line
int main()
{
do  
{  
   printf("Hello !!"); // main body of the infinite do while loop..  
}
while(1);  // 1 is considered as true and 0 as false
}

Output:

Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello!!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello !!Hello