diff --git a/challenges/caesar-cipher/solutions/c/function/character.h b/challenges/caesar-cipher/solutions/c/function/character.h
index 1c1851b..0fab88f 100644
--- a/challenges/caesar-cipher/solutions/c/function/character.h
+++ b/challenges/caesar-cipher/solutions/c/function/character.h
@@ -1,5 +1,5 @@
-#ifndef CHARACTER_H
-#define CHARACTER_H
+#ifndef __CHARACTER__
+#define __CHARACTER__
 
 /**
  * @brief Append a character to a string, assuming string points to an array
diff --git a/challenges/caesar-cipher/solutions/c/function/input.h b/challenges/caesar-cipher/solutions/c/function/input.h
index 9cd0a22..d432398 100644
--- a/challenges/caesar-cipher/solutions/c/function/input.h
+++ b/challenges/caesar-cipher/solutions/c/function/input.h
@@ -1,5 +1,5 @@
-#ifndef INPUT_H
-#define INPUT_H
+#ifndef __INPUT__
+#define __INPUT__
 
 /**
  * @brief Read a line from stdin.
diff --git a/challenges/caesar-cipher/solutions/c/function/string.h b/challenges/caesar-cipher/solutions/c/function/string.h
index ab9281f..d775145 100644
--- a/challenges/caesar-cipher/solutions/c/function/string.h
+++ b/challenges/caesar-cipher/solutions/c/function/string.h
@@ -1,5 +1,5 @@
-#ifndef STRING_H
-#define STRING_H
+#ifndef __STRING__
+#define __STRING__
 
 #define ALPHABET "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
 
diff --git a/challenges/camel-case/solutions/c/function/character.h b/challenges/camel-case/solutions/c/function/character.h
index a013fe6..b49dd7a 100644
--- a/challenges/camel-case/solutions/c/function/character.h
+++ b/challenges/camel-case/solutions/c/function/character.h
@@ -1,5 +1,5 @@
-#ifndef CHARACTER_H
-#define CHARACTER_H
+#ifndef __CHARACTER__
+#define __CHARACTER__
 
 /**
  * @brief Append a character to a string, assuming string points to an array
diff --git a/challenges/camel-case/solutions/c/function/input.h b/challenges/camel-case/solutions/c/function/input.h
index 9cd0a22..d432398 100644
--- a/challenges/camel-case/solutions/c/function/input.h
+++ b/challenges/camel-case/solutions/c/function/input.h
@@ -1,5 +1,5 @@
-#ifndef INPUT_H
-#define INPUT_H
+#ifndef __INPUT__
+#define __INPUT__
 
 /**
  * @brief Read a line from stdin.
diff --git a/challenges/camel-case/solutions/c/function/string.h b/challenges/camel-case/solutions/c/function/string.h
index 4680c5c..7584bd1 100644
--- a/challenges/camel-case/solutions/c/function/string.h
+++ b/challenges/camel-case/solutions/c/function/string.h
@@ -1,5 +1,5 @@
-#ifndef STRING_H
-#define STRING_H
+#ifndef __STRING__
+#define __STRING__
 
 /**
  * @brief Removes all whitespace from the start of a string.
diff --git a/challenges/first-non-repeating-character/solutions/c/function/character.h b/challenges/first-non-repeating-character/solutions/c/function/character.h
index 1c1851b..0fab88f 100644
--- a/challenges/first-non-repeating-character/solutions/c/function/character.h
+++ b/challenges/first-non-repeating-character/solutions/c/function/character.h
@@ -1,5 +1,5 @@
-#ifndef CHARACTER_H
-#define CHARACTER_H
+#ifndef __CHARACTER__
+#define __CHARACTER__
 
 /**
  * @brief Append a character to a string, assuming string points to an array
diff --git a/challenges/first-non-repeating-character/solutions/c/function/input.h b/challenges/first-non-repeating-character/solutions/c/function/input.h
index 9cd0a22..d432398 100644
--- a/challenges/first-non-repeating-character/solutions/c/function/input.h
+++ b/challenges/first-non-repeating-character/solutions/c/function/input.h
@@ -1,5 +1,5 @@
-#ifndef INPUT_H
-#define INPUT_H
+#ifndef __INPUT__
+#define __INPUT__
 
 /**
  * @brief Read a line from stdin.
diff --git a/challenges/first-non-repeating-character/solutions/c/function/string.h b/challenges/first-non-repeating-character/solutions/c/function/string.h
index 425a76f..86d85b6 100644
--- a/challenges/first-non-repeating-character/solutions/c/function/string.h
+++ b/challenges/first-non-repeating-character/solutions/c/function/string.h
@@ -1,5 +1,5 @@
-#ifndef STRING_H
-#define STRING_H
+#ifndef __STRING__
+#define __STRING__
 
 #include <stdlib.h>
 
diff --git a/challenges/prime-numbers-decomposition/solutions/c/function/solution.c b/challenges/prime-numbers-decomposition/solutions/c/function/solution.c
index fe9dd8f..f8cbea5 100644
--- a/challenges/prime-numbers-decomposition/solutions/c/function/solution.c
+++ b/challenges/prime-numbers-decomposition/solutions/c/function/solution.c
@@ -47,13 +47,13 @@ int* prime_numbers_decomposition(int number, int* decomposition_length) {
   int dividend = number;
   while (total != number) {
     int divider = 2;
-    int reste = 0;
+    int remainder = 0;
     int quotient = 0;
     do {
-      reste = dividend % divider;
+      remainder = dividend % divider;
       quotient = dividend / divider;
       divider++;
-    } while (reste != 0);
+    } while (remainder != 0);
     divider--;
     decomposition[*decomposition_length - 1] = divider;
     *decomposition_length = *decomposition_length + 1;