Add the syntax "For infinite loop " (#21382)

* Add the syntax "For infinite loop "

* Shifted additions around to be less confusing

guide/english/c/for/index.md

@@ -23,7 +23,7 @@ The initialization statement is executed only once. Then, the test expression is
 
 The for loop is commonly used when the number of iterations is known.
 
-## Example
+#### Example
 ```c
 #include <stdio.h>
 
@@ -37,7 +37,7 @@ int main () {
 }
 ```
 
-## Output:
+#### Output:
 ```shell
 > Item on index 0 is 1
 > Item on index 1 is 2
@@ -88,3 +88,12 @@ main ()
 
 
 
+## Syntax of For infinite loop
+
+```c
+for ( ; ; ) {
+   statement(s);
+}
+```
+
+An infinite loop occurs when the condition will never be met, due to some inherent characteristic of the loop. An infinite loop also called an endless loop, and it is a piece of coding that lacks a functional exit so that it repeats indefinitely.