Merge 'master' of github.com:adambard/learnxinyminutes-docs

1 files changed, 58 insertions, 3 deletions

diff --git a/c.html.markdown b/c.html.markdown
index 3339032f..a8f71057 100644
--- a/c.html.markdown
+++ b/c.html.markdown
@@ -6,8 +6,8 @@ contributors:
     - ["Árpád Goretity", "http://twitter.com/H2CO3_iOS"]
     - ["Jakub Trzebiatowski", "http://cbs.stgn.pl"]
     - ["Marco Scannadinari", "https://marcoms.github.io"]
+    - ["Zachary Ferguson", "https://github.io/zfergus2"]
     - ["himanshu", "https://github.com/himanshu81494"]
-
 ---
 
 Ah, C. Still **the** language of modern high-performance computing.
@@ -54,6 +54,8 @@ int function_2(void);
 // Must declare a 'function prototype' before main() when functions occur after
 // your main() function.
 int add_two_ints(int x1, int x2); // function prototype
+// although `int add_two_ints(int, int);` is also valid (no need to name the args),
+// it is recommended to name arguments in the prototype as well for easier inspection
 
 // Your program's entry point is a function called
 // main with an integer return type.
@@ -74,6 +76,9 @@ int main (int argc, char** argv)
   ///////////////////////////////////////
   // Types
   ///////////////////////////////////////
+  
+  // All variables MUST be declared at the top of the current block scope
+  // we declare them dynamically along the code for the sake of the tutorial
 
   // ints are usually 4 bytes
   int x_int = 0;
@@ -232,7 +237,7 @@ int main (int argc, char** argv)
   0 || 1; // => 1 (Logical or)
   0 || 0; // => 0
 
-  // Conditional expression ( ? : )
+  // Conditional ternary expression ( ? : )
   int e = 5;
   int f = 10;
   int z;
@@ -302,6 +307,8 @@ int main (int argc, char** argv)
   for (i = 0; i <= 5; i++) {
     ; // use semicolon to act as the body (null statement)
   }
+  // Or
+  for (i = 0; i <= 5; i++);
 
   // branching with multiple choices: switch()
   switch (a) {
@@ -678,8 +685,56 @@ typedef void (*my_fnp_type)(char *);
 // ,                                 | left to right //
 //---------------------------------------------------//
 
-```
+/******************************* Header Files **********************************
+
+Header files are an important part of c as they allow for the connection of c 
+source files and can simplify code and definitions by seperating them into 
+seperate files.
+
+Header files are syntaxtically similar to c source files but reside in ".h" 
+files. They can be included in your c source file by using the precompiler 
+command #include "example.h", given that example.h exists in the same directory 
+as the c file.
+*/
+
+/* A safe guard to prevent the header from being defined too many times. This */
+/* happens in the case of circle dependency, the contents of the header is    */
+/* already defined.                                                           */
+#ifndef EXAMPLE_H /* if EXAMPLE_H is not yet defined. */
+#define EXAMPLE_H /* Define the macro EXAMPLE_H. */
+
+/* Other headers can be included in headers and therefore transitively */
+/* included into files that include this header.                       */
+#include <string.h>
 
+/* Like c source files macros can be defined in headers and used in files */
+/* that include this header file.                                         */
+#define EXAMPLE_NAME "Dennis Ritchie"
+/* Function macros can also be defined. */
+#define ADD(a, b) (a + b)
+
+/* Structs and typedefs can be used for consistency between files. */
+typedef struct node
+{
+    int val;
+    struct node *next;
+} Node;
+
+/* So can enumerations. */
+enum traffic_light_state {GREEN, YELLOW, RED};
+
+/* Function prototypes can also be defined here for use in multiple files,  */
+/* but it is bad practice to define the function in the header. Definitions */
+/* should instead be put in a c file.                                       */
+Node createLinkedList(int *vals, int len);
+
+/* Beyond the above elements, other definitions should be left to a c source */
+/* file. Excessive includeds or definitions should, also not be contained in */
+/* a header file but instead put into separate headers or a c file.          */
+
+#endif /* End of the if precompiler directive. */
+
+```
 ## Further Reading
 
 Best to find yourself a copy of [K&R, aka "The C Programming Language"](https://en.wikipedia.org/wiki/The_C_Programming_Language)