Added a warning to the article (#22219)

* Added a warning to the article

Added a warning with an example, which can occur on older compilers.

* fix(guide): c for loop iterator misnomer

declaration not initialisation

guide/english/c/for/index.md

@@ -99,3 +99,35 @@ for ( ; ; ) {
 ```
 
 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.
+
+
+## Warning!
+
+Some older versions of compilers don't support declaration inside the for loop:
+```C
+#include <stdio.h>
+
+int main () {
+
+    int array[] = {1, 2, 3, 4, 5};
+
+    for (int i = 0; i < 5; i++) {      // The int i = 0 will show you an error on older compiler versions
+    	printf("Item on index %d is %d\n", i, array[i]);
+    }
+}
+```
+
+You can solve this problem if you declare the variable before:
+```C
+#include <stdio.h>
+
+int main () {
+
+    int array[] = {1, 2, 3, 4, 5};
+    int i;        // You declare the variable before the for loop
+
+    for (i = 0; i < 5; i++) {       // Now you won't have a problem
+    	printf("Item on index %d is %d\n", i, array[i]);
+    }
+}
+```