Infinite Loop in C: “Infinite loop,” as the name suggests, refers to an endless loop. It is a sequence of instructions that will not end unless an external intervention happens. In other words, it is a loop that iterates indefinitely and does end. It is also known as an indefinite loop or endless loop. Most of the time, indefinite loops happen by mistake. That does not mean they are not required. An infinite loop is generally used in an application or a program where the code and data are kept safe. An endless loop is of great help in web servers, operating systems, applications such as games, and where the application needs to be running for infinite time.

Looping is repeating a set of instructions until an intended condition is met. An infinite loop is a condition where the condition will nowhere be completed due to a particular characteristic. An infinite loop or an endless whether gives a continuous output or no output at all.

An infinite loop can either be intentional or unintentional.

  • Unintentional or unintended loop: An infinite loop created unintentionally will have an error or bug in the specific code, either by mistake or by specifying the condition that never becomes false. Consider an instance where a programmer intends to iterate over a sequence of nodes present as a tree or a list within a data structure, executing the loop once for each node. Inappropriate links can create a reference loop in a data structure, where one node links to another node that appears earlier in the sequence. This situation makes that part of the data structure into a ring, causing puzzled code to loop forever.
  • Intentional loop or intended loop: An intentional infinite loop explicitly creates to achieve a specific requirement in an application. The loop structure is used to create a deliberate or explicit infinite loop, and the code runs in a loop repeatedly or infinite times. There might be few situations, such as games that typically have no exit condition in the main loop, in the same way as an operating system. In such circumstances, the loop runs until the console is powered off.

Some of the threads might be executing inside the infinite loops in multi-threaded programs without causing the entire program to be stuck in an infinite loop. If the main thread still exists, then all the processes are forcefully stopped. Thus, all execution and the compilation end, and the program eventually terminates. These threads inside the infinite loops can perform tasks or can be in a blocked state waiting for input and resume the execution every time when input is received.

Types:

For loop in C

Syntax:

Within the for statement, the three parts of initialized loop, condition, and increment or decrement are not defined, which means there is no start and end value, leading to an infinite loop.

 Eg:

While loop in C

Syntax:

Eg:

Do-while loop in C

Syntax:

Eg:

Go to statement in C

Syntax:

Eg:

C macros in C

With respect to loop, we can use macro that defines an infinite loop.

Eg:

Macro is defined where value is for( ; ; ). Later in the main function, the macro function is defined. Hence, whenever the name of macro comes, it gets replaced by its value. All the above examples create an infinite loop and lead to endless looping.

Loops can be terminated at any time, including the infinite loop, using a break statement within the loop where there will be a repeating group of statements. When break statements are encountered, looping stops, and program execution picks up with the next statement after the loop.

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