change header guard

TylerMSFT · TylerMSFT · commit 66156d9386bd · 2021-04-22T09:41:50.000-07:00
diff --git a/docs/build/walkthrough-header-units.md b/docs/build/walkthrough-header-units.md
@@ -55,19 +55,22 @@ In this example, you'll compile a header file as a header unit. Start by creatin
     
     int main()
     {
-        PrintPythogoreanTriple(2,3);
+        PrintPythagoreanTriple(2,3);
         return 0;
     }
     ```
 1. Add a header file called `Pythagorean.h`, and replace its content with this code:
     ```cpp
-    #pragma once
+    #ifndef PYTHAGOREAN
+    #define PYTHAGOREAN
+
     #include <iostream>
     
-    void PrintPythogoreanTriple(int a, int b)
+    void PrintPythagoreanTriple(int a, int b)
     {
         std::cout << "Pythagorean triple a:" << a << " b:" << b << " c:" << a*a + b*b << std::endl;
     }
+    #endif
     ```
 
 To enable header units, first set the **C++ Language Standard** to [`/std:c++latest`](./reference/std-specify-language-standard-version.md).

Original file line number	Diff line number	Diff line change
`@@ -55,19 +55,22 @@ In this example, you'll compile a header file as a header unit. Start by creatin`
`55`	`55`
`56`	`56`	`int main()`
`57`	`57`	`{`
`58`		`- PrintPythogoreanTriple(2,3);`
	`58`	`+ PrintPythagoreanTriple(2,3);`
`59`	`59`	`return 0;`
`60`	`60`	`}`
`61`	`61`	```
`62`	`62`	1. Add a header file called `Pythagorean.h`, and replace its content with this code:
`63`	`63`	```cpp
`64`		`- #pragma once`
	`64`	`+ #ifndef PYTHAGOREAN`
	`65`	`+ #define PYTHAGOREAN`
	`66`	`+`
`65`	`67`	`#include <iostream>`
`66`	`68`
`67`		`- void PrintPythogoreanTriple(int a, int b)`
	`69`	`+ void PrintPythagoreanTriple(int a, int b)`
`68`	`70`	`{`
`69`	`71`	`std::cout << "Pythagorean triple a:" << a << " b:" << b << " c:" << aa + bb << std::endl;`
`70`	`72`	`}`
	`73`	`+ #endif`
`71`	`74`	```
`72`	`75`
`73`	`76`	To enable header units, first set the C++ Language Standard to [`/std:c++latest`](./reference/std-specify-language-standard-version.md).