Edits

1 files changed, 117 insertions, 133 deletions

diff --git a/c.html.markdown b/c.html.markdown
index 00b13cb0..24a96463 100644
--- a/c.html.markdown
+++ b/c.html.markdown
@@ -1,11 +1,9 @@
 ---
-- name: c
-- category: language
-- language: c
-- filename: learnc.c
-- contributors:
- - [Adam Bard](http://adambard.com/)
- - [Árpád Goretity](http://twitter.com/H2CO3_iOS)
+language: c
+filename: learnc.c
+contributors:
+    - ["Adam Bard", "http://adambard.com/"]
+    - ["Árpád Goretity", "http://twitter.com/H2CO3_iOS"]
 
 ---
 
@@ -27,17 +25,10 @@ Multi-line comments look like this. They work in C89 as well.
 #include <stdio.h>
 #include <string.h>
 
-// file names between <angle brackets> are headers from the C standard library.
-// They are searched for by the preprocessor in the system include paths
-// (usually /usr/lib on Unices, can be controlled with the -I<dir> option if you are using GCC or clang.)
+// (File names between <angle brackets> are headers from the C standard library.)
 // For your own headers, use double quotes instead of angle brackets:
 #include "my_header.h"
 
-// The C preprocessor introduces an almost fully-featured macro language. It's useful, but
-// it can be confusing (and what's even worse, it can be misused). Read the
-// Wikipedia article on the C preprocessor for further information:
-// http://en.wikipedia.org/wiki/C_preprocessor
-
 // Declare function signatures in advance in a .h file, or at the top of
 // your .c file.
 void function_1();
@@ -50,132 +41,117 @@ int main() {
     // %d is an integer, \n is a newline
     printf("%d\n", 0); // => Prints 0
     // All statements must end with a semicolon
-    
+
     ///////////////////////////////////////
     // Types
     ///////////////////////////////////////
-    
-    // You have to declare variables before using them. A variable declaration
-    // requires you to specify its type; a variable's type determines its size
-    // in bytes.
-    
+
     // ints are usually 4 bytes 
     int x_int = 0;
-    
+
     // shorts are usually 2 bytes
     short x_short = 0;
-    
+
     // chars are guaranteed to be 1 byte
     char x_char = 0;
     char y_char = 'y'; // Char literals are quoted with ''
-    
+
     // longs are often 4 to 8 bytes; long longs are guaranteed to be at least
     // 64 bits
     long x_long = 0;
     long long x_long_long = 0; 
-    
+
     // floats are usually 32-bit floating point numbers
     float x_float = 0.0;
-    
+
     // doubles are usually 64-bit floating-point numbers
     double x_double = 0.0;
-    
-    // Integral types may be unsigned. This means they can't be negative, but
-    // the maximum value of an unsigned variable is greater than the maximum
-    // signed value of the same size.
-    unsigned char ux_char;
+
+    // Integral types may be unsigned.
     unsigned short ux_short;
     unsigned int ux_int;
     unsigned long long ux_long_long;
-    
-    // Other than char, which is always 1 byte (but not necessarily 8 bits!),
-    // these types vary in size depending on your machine and compiler.
-    // sizeof(T) gives you the size of a variable with type T in 
-    // bytes so you can express the size of these types in a portable way.
-    // sizeof(obj) yields the size of an actual expression (variable, literal, etc.).
-    // For example,
+
+    // sizeof(T) gives you the size of a variable with type T in bytes
+    // sizeof(obj) yields the size of the expression (variable, literal, etc.).
     printf("%zu\n", sizeof(int)); // => 4 (on most machines with 4-byte words)
-    
-    
-    // It's worth noting that if the argument of the `sizeof` operator is not a type but an expression,
-    // then its argument is not evaluated except VLAs (see below). Also, `sizeof()` is an operator, not a function,
-    // furthermore, the value it yields is a compile-time constant (except when used on VLAs, again.)
+
+
+    // If the argument of the `sizeof` operator an expression, then its argument
+    // is not evaluated (except VLAs (see below)).
+    // The value it yields in this case is a compile-time constant.
     int a = 1;
     size_t size = sizeof(a++); // a++ is not evaluated
     printf("sizeof(a++) = %zu where a = %d\n", size, a);
-    // the above code prints "sizeof(a++) = 4 where a = 1" (on a usual 32-bit architecture)
-    
+    // prints "sizeof(a++) = 4 where a = 1" (on a 32-bit architecture)
+
     // Arrays must be initialized with a concrete size.
     char my_char_array[20]; // This array occupies 1 * 20 = 20 bytes
     int my_int_array[20]; // This array occupies 4 * 20 = 80 bytes
                           // (assuming 4-byte words)
-    
-    
+
+
     // You can initialize an array to 0 thusly:
     char my_array[20] = {0};
-    
+
     // Indexing an array is like other languages -- or,
     // rather, other languages are like C
     my_array[0]; // => 0
-    
+
     // Arrays are mutable; it's just memory!
     my_array[1] = 2;
     printf("%d\n", my_array[1]); // => 2
-    
-    // In C99 (and as an optional feature in C11), variable-length arrays (VLAs) can be declared as well.
-    // The size of such an array need not be a compile time constant:
+
+    // In C99 (and as an optional feature in C11), variable-length arrays (VLAs)
+    // can be declared as well. The size of such an array need not be a compile
+    // time constant:
     printf("Enter the array size: "); // ask the user for an array size
     char buf[0x100];
     fgets(buf, sizeof buf, stdin);
-    size_t size = strtoul(buf, NULL, 10); // strtoul parses a string to an unsigned integer
+
+    // strtoul parses a string to an unsigned integer
+    size_t size = strtoul(buf, NULL, 10);
     int var_length_array[size]; // declare the VLA
     printf("sizeof array = %zu\n", sizeof var_length_array);
-    
+
     // A possible outcome of this program may be:
-    Enter the array size: 10
-    sizeof array = 40
-    
+    // > Enter the array size: 10
+    // > sizeof array = 40
+
     // Strings are just arrays of chars terminated by a NUL (0x00) byte,
     // represented in strings as the special character '\0'.
     // (We don't have to include the NUL byte in string literals; the compiler
     //  inserts it at the end of the array for us.)
     char a_string[20] = "This is a string";
     printf("%s\n", a_string); // %s formats a string
-    
-    /*
-     You may have noticed that a_string is only 16 chars long.
-     Char #17 is the NUL byte. 
-     Chars #18, 19 and 20 are 0 as well - if an initializer list (in this case, the string literal)
-     has less elements than the array it is initializing, then excess array elements are implicitly
-     initialized to zero. This is why int ar[10] = { 0 } works as expected intuitively.
-    */
-    
+
     printf("%d\n", a_string[16]); // => 0
-    
-    // So string literals are strings enclosed within double quotes, but if we have characters
-    // between single quotes, that's a character literal.
+    // i.e., byte #17 is 0 (as are 18, 19, and 20)
+
+    // If we have characters between single quotes, that's a character literal.
     // It's of type `int`, and *not* `char` (for historical reasons).
     int cha = 'a'; // fine
-    char chb = 'a'; // fine too (implicit conversion from int to char - truncation)
-    
+    char chb = 'a'; // fine too (implicit conversion from int to char)
+
     ///////////////////////////////////////
     // Operators
     ///////////////////////////////////////
-    
+
     int i1 = 1, i2 = 2; // Shorthand for multiple declaration
     float f1 = 1.0, f2 = 2.0;
-    
+
     // Arithmetic is straightforward
     i1 + i2; // => 3
     i2 - i1; // => 1
     i2 * i1; // => 2
     i1 / i2; // => 0 (0.5, but truncated towards 0)
-    
-    f1 / f2; // => 0.5, plus or minus epsilon - floating-point numbers and calculations are not exact
-    
+
+    f1 / f2; // => 0.5, plus or minus epsilon
+    // Floating-point numbers and calculations are not exact
+
     // Modulo is there as well
     11 % 3; // => 2
-    
+
     // Comparison operators are probably familiar, but
     // there is no boolean type in c. We use ints instead.
     // (Or _Bool or bool in C99.)
@@ -187,14 +163,14 @@ int main() {
     3 < 2; // => 0
     2 <= 2; // => 1
     2 >= 2; // => 1
-    
+
     // C is not Python - comparisons don't chain.
     int a = 1;
     // WRONG:
     int between_0_and_2 = 0 < a < 2;
     // Correct:
     int between_0_and_2 = 0 < a && a < 2;
-    
+
     // Logic works on ints
     !3; // => 0 (Logical not)
     !0; // => 1
@@ -202,7 +178,7 @@ int main() {
     0 && 1; // => 0
     0 || 1; // => 1 (Logical or)
     0 || 0; // => 0
-    
+
     // Bitwise operators!
     ~0x0F; // => 0xF0 (bitwise negation, "1's complement")
     0x0F & 0xF0; // => 0x00 (bitwise AND)
@@ -210,17 +186,17 @@ int main() {
     0x04 ^ 0x0F; // => 0x0B (bitwise XOR)
     0x01 << 1; // => 0x02 (bitwise left shift (by 1))
     0x02 >> 1; // => 0x01 (bitwise right shift (by 1))
-    
-    // Be careful when shifting signed integers - the following are all undefined behavior:
+
+    // Be careful when shifting signed integers - the following are undefined:
     // - shifting into the sign bit of a signed integer (int a = 1 << 32)
     // - left-shifting a negative number (int a = -1 << 2)
-    // - shifting by an offset which is more than or equal to the width of the type of the LHS:
+    // - shifting by an offset which is >= the width of the type of the LHS:
     //   int a = 1 << 32; // UB if int is 32 bits wide
-    
+
     ///////////////////////////////////////
     // Control Structures
     ///////////////////////////////////////
-    
+
     if (0) {
       printf("I am never run\n");
     } else if (0) {
@@ -228,36 +204,38 @@ int main() {
     } else {
       printf("I print\n");
     }
-    
+
     // While loops exist
     int ii = 0;
     while (ii < 10) {
-        printf("%d, ", ii++); // ii++ increments ii in-place, after yielding its value ("postincrement").
+        printf("%d, ", ii++); // ii++ increments ii in-place
+                              // after yielding its value ("postincrement").
     } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, "
-    
+
     printf("\n");
-    
+
     int kk = 0;
     do {
         printf("%d, ", kk);
-    } while (++kk < 10); // ++kk increments kk in-place, and yields the already incremented value ("preincrement")
+    } while (++kk < 10); // ++kk increments kk in-place, and yields
+                         // the already incremented value ("preincrement")
     // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, "
-    
+
     printf("\n");
-    
+
     // For loops too
     int jj;
     for (jj=0; jj < 10; jj++) {
         printf("%d, ", jj);
     } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, "
-    
+
     printf("\n");
-    
+
     // branching with multiple choices: switch()
     switch (some_integral_expression) {
     case 0: // labels need to be integral *constant* epxressions
         do_stuff();
-        break; // if you don't break, control flow falls over labels - you usually don't want that.
+        break; // if you don't break, control flow falls over labels
     case 1:
         do_something_else();
         break;
@@ -267,73 +245,74 @@ int main() {
         exit(-1);
         break;
     }
-        
     
+
     ///////////////////////////////////////
     // Typecasting
     ///////////////////////////////////////
-    
+
     // Every value in C has a type, but you can cast one value into another type
     // if you want (with some constraints).
-    
+
     int x_hex = 0x01; // You can assign vars with hex literals
-    
+
     // Casting between types will attempt to preserve their numeric values
     printf("%d\n", x_hex); // => Prints 1
     printf("%d\n", (short) x_hex); // => Prints 1
     printf("%d\n", (char) x_hex); // => Prints 1
-    
+
     // Types will overflow without warning
     printf("%d\n", (unsigned char) 257); // => 1 (Max char = 255 if char is 8 bits long)
-    // printf("%d\n", (unsigned char) 257); would be undefined behavior - `char' is usually signed
-    // on most modern systems, and signed integer overflow invokes UB.
-    // Also, for determining the maximal value of a `char`, a `signed char` and an `unisigned char`,
+
+    // For determining the max value of a `char`, a `signed char` and an `unisigned char`,
     // respectively, use the CHAR_MAX, SCHAR_MAX and UCHAR_MAX macros from <limits.h>
-    
+
     // Integral types can be cast to floating-point types, and vice-versa.
     printf("%f\n", (float)100); // %f formats a float
     printf("%lf\n", (double)100); // %lf formats a double
     printf("%d\n", (char)100.0);
-    
+
     ///////////////////////////////////////
     // Pointers
     ///////////////////////////////////////
-    
+
     // A pointer is a variable declared to store a memory address. Its declaration will
     // also tell you the type of data it points to. You can retrieve the memory address 
     // of your variables, then mess with them.
-    
+
     int x = 0;
     printf("%p\n", (void *)&x); // Use & to retrieve the address of a variable
     // (%p formats an object pointer of type void *)
     // => Prints some address in memory;
-    
-    
+
+
     // Pointers start with * in their declaration
     int *px, not_a_pointer; // px is a pointer to an int
     px = &x; // Stores the address of x in px
     printf("%p\n", (void *)px); // => Prints some address in memory
     printf("%zu, %zu\n", sizeof(px), sizeof(not_a_pointer));
     // => Prints "8, 4" on a typical 64-bit system
-    
+
     // To retreive the value at the address a pointer is pointing to,
     // put * in front to de-reference it.
-    // Note: yes, it may be confusing that '*' is used for _both_ declaring a pointer and dereferencing it.
-    printf("%d\n", *px); // => Prints 0, the value of x, which is what px is pointing to the address of
-    
+    // Note: yes, it may be confusing that '*' is used for _both_ declaring a
+    // pointer and dereferencing it.
+    printf("%d\n", *px); // => Prints 0, the value of x
+
     // You can also change the value the pointer is pointing to.
     // We'll have to wrap the de-reference in parenthesis because
     // ++ has a higher precedence than *.
     (*px)++; // Increment the value px is pointing to by 1
     printf("%d\n", *px); // => Prints 1
     printf("%d\n", x); // => Prints 1
-    
-    int x_array[20]; // Arrays are a good way to allocate a contiguous block of memory
+
+    // Arrays are a good way to allocate a contiguous block of memory
+    int x_array[20];
     int xx;
     for (xx = 0; xx < 20; xx++) {
         x_array[xx] = 20 - xx;
     } // Initialize x_array to 20, 19, 18,... 2, 1
-    
+
     // Declare a pointer of type int and initialize it to point to x_array
     int* x_ptr = x_array;
     // x_ptr now points to the first element in the array (the integer 20). 
@@ -342,50 +321,52 @@ int main() {
     // it decays into (implicitly converted to) a pointer.
     // Exceptions: when the array is the argument of the `&` (address-od) operator:
     int arr[10];
-    int (*ptr_to_arr)[10] = &arr; // &arr is NOT of type `int *`! It's of type "pointer to array" (of ten `int`s).
+    int (*ptr_to_arr)[10] = &arr; // &arr is NOT of type `int *`!
+                                  // It's of type "pointer to array" (of ten `int`s).
     // or when the array is a string literal used for initializing a char array:
     char arr[] = "foobarbazquirk";
     // or when it's the argument of the `sizeof` or `alignof` operator:
     int arr[10];
     int *ptr = arr; // equivalent with int *ptr = &arr[0];
     printf("%zu %zu\n", sizeof arr, sizeof ptr); // probably prints "40, 4" or "40, 8"
-    
+
 
     // Pointers are incremented and decremented based on their type
     // (this is called pointer arithmetic)
     printf("%d\n", *(x_ptr + 1)); // => Prints 19
     printf("%d\n", x_array[1]); // => Prints 19
-    
+
     // You can also dynamically allocate contiguous blocks of memory with the
     // standard library function malloc, which takes one argument of type size_t
     // representing the number of bytes to allocate (usually from the heap, although this
     // may not be true on e. g. embedded systems - the C standard says nothing about it).
     int *my_ptr = malloc(sizeof(*my_ptr) * 20);
     for (xx = 0; xx < 20; xx++) {
-        *(my_ptr + xx) = 20 - xx; // my_ptr[xx] = 20-xx would also work here, and it's also more readable
+        *(my_ptr + xx) = 20 - xx; // my_ptr[xx] = 20-xx
     } // Initialize memory to 20, 19, 18, 17... 2, 1 (as ints)
-    
+
     // Dereferencing memory that you haven't allocated gives
     // "unpredictable results" - the program is said to invoke "undefined behavior"
     printf("%d\n", *(my_ptr + 21)); // => Prints who-knows-what? It may even crash.
-    
+
     // When you're done with a malloc'd block of memory, you need to free it, 
     // or else no one else can use it until your program terminates
     // (this is called a "memory leak"):
     free(my_ptr);
-    
+
     // Strings are arrays of char, but they are usually represented as a
     // pointer-to-char (which is a pointer to the first element of the array).
     // It's good practice to use `const char *' when referring to a string literal,
     // since string literals shall not be modified (i. e. "foo"[0] = 'a' is ILLEGAL.)
     const char *my_str = "This is my very own string literal";
     printf("%c\n", *my_str); // => 'T'
-    
-    // This is not the case if the string is an array (potentially initialized with a string literal)
+
+    // This is not the case if the string is an array
+    // (potentially initialized with a string literal)
     // that resides in writable memory, as in:
     char foo[] = "foo";
     foo[0] = 'a'; // this is legal, foo now contains "aoo"
-    
+
     function_1();
 } // end main function
 
@@ -435,17 +416,17 @@ printf("%s\n", c); // => ".tset a si sihT"
 typedef int my_type;
 my_type my_type_var = 0;
 
-// Structs are just collections of data, the members are allocated sequentially, in the order they are written:
+// Structs are just collections of data, the members are allocated sequentially,
+// in the order they are written:
 struct rectangle {
     int width;
     int height;
 };
 
-// it's generally not true that sizeof(struct rectangle) == sizeof(int) + sizeof(int) due to
-// potential padding between the structure members (this is for alignment reasons. Probably won't
-// happen if all members are of the same type, but watch out!
-// See http://stackoverflow.com/questions/119123/why-isnt-sizeof-for-a-struct-equal-to-the-sum-of-sizeof-of-each-member
-// for further information.
+// It's not generally true that
+// sizeof(struct rectangle) == sizeof(int) + sizeof(int)
+// due to potential padding between the structure members (this is for alignment
+// reasons). [1]
 
 void function_1()
 {
@@ -473,7 +454,8 @@ int area(rect r)
     return r.width * r.height;
 }
 
-// if you have large structs, you can pass them "by pointer" to avoid copying the whole struct:
+// if you have large structs, you can pass them "by pointer" to avoid copying
+// the whole struct:
 int area(const rect *r)
 {
     return r->width * r->height;
@@ -527,3 +509,5 @@ Readable code is better than clever code and fast code. For a good, sane coding
 [Linux kernel coding stlye](https://www.kernel.org/doc/Documentation/CodingStyle).
 
 Other than that, Google is your friend.
+
+[1] http://stackoverflow.com/questions/119123/why-isnt-sizeof-for-a-struct-equal-to-the-sum-of-sizeof-of-each-member