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--- header-guard [May 14, 2026 at 12:50] – created yanevskiv
+++ header-guard [May 14, 2026 at 13:01] (current) – yanevskiv
@@ Line 1: / Line 1: @@
 # Header guard
-**Header guards** are used
+**Header guards** are a pattern used in C and C++ programming languages when writing header files. Header files (.h files) are files that are included in source files (.c and .cpp files) near the top (hence the name) using the `#include <...>` directive. They are used to allow multiple inclusions of the same file but prevent multiple definition errors.
+Header guards follow the same general pattern:
+```c
+#ifndef __HEADER_GUARD_H__
+#define __HEADER_GUARD_H__
+// ...
+#endif /* __HEADER_GUARD_H__ (This is just a comment) */
 ```
-// my_header.h
-#ifndef __MY_HEADER_H__
-#define __MY_HEADER_H__
-// ... your code goes here ...
+In C and C++ programming languages, `#include` is nothing but text substitution. If you include something multiple times
-#endif /* __MY_HEADER_H__ */
+## Example
+A prototypical example of a header guard is the following.
+```c
+// hello_world.h
+#ifndef __HELLO_WORLD_H__
+#define __HELLO_WORLD_H__
+struct Hello {
+    const char *text = "world";
+};
+#endif /* __HELLO_WORLD_H__ */
 ```
+This allows multiple inclusion of "hello\_world.h"
+```c
+// main.c
+#include <hello_world.h>
+#include <hello_world.h>
+int main() {
+    Hello world;
+    return 0;
+}
+```