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+---
+language: c
+author: Adam Bard
+author_url: http://adambard.com/
+---
+
+Ah, C. Still the language of modern high-performance computing.
+
+C is the lowest-level language most programmers will ever use, but
+it more than makes up for it with raw speed. Just be aware of its manual
+memory management and C will take you as far as you need to go.
+
+```c
+// Single-line comments start with //
+/*
+Multi-line comments look like this.
+*/
+
+// Import headers with #include
+#include <stdlib.h>
+#include <stdio.h>
+
+// Declare function signatures in advance in a .h file, or at the top of
+// your .c file.
+void function_1();
+void function_2();
+
+// Your program's entry point is a function called
+// main with an integer return type.
+int main(){
+
+// print output using printf, for "print formatted"
+// %d is an integer, \n is a newline
+printf("%d\n", 0); // => Prints 0
+// All statements must end with a semicolon
+
+///////////////////////////////////////
+// Types
+///////////////////////////////////////
+
+// Variables must always be declared with a type.
+
+// 32-bit integer
+int x_int = 0;
+
+// 16-bit integer
+short x_short = 0;
+
+// 8-bit integer, aka 1 byte
+char x_char = 0;
+char y_char = 'y'; // Char literals are quoted with ''
+
+long x_long = 0; // Still 32 bytes for historical reasons
+long long x_long_long = 0; // Guaranteed to be at least 64 bytes
+
+// 32-bit floating-point decimal
+float x_float = 0.0;
+
+// 64-bit floating-point decimal
+double x_double = 0.0;
+
+// Integer types may be unsigned
+unsigned char ux_char;
+unsigned short ux_short;
+unsigned int ux_int;
+unsigned long long ux_long_long;
+
+// 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
+
+
+// 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
+
+// Strings are just lists of chars terminated by a null (0x00) byte.
+char a_string[20] = "This is a string";
+
+/*
+You may have noticed that a_string is only 16 chars long.
+Char #17 is a null byte, 0x00 aka \0. 
+Chars #18, 19 and 20 have undefined values.
+*/
+
+printf("%d\n", a_string[16]);
+
+///////////////////////////////////////
+// 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
+
+// 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.
+// 0 is false, anything else is true
+3 == 2; // => 0 (false)
+3 != 2; // => 1 (true)
+3 > 2; // => 1
+3 < 2; // => 0
+2 <= 2; // => 1
+2 >= 2; // => 1
+
+// Logic works on ints
+!3; // => 0 (Logical not)
+!0; // => 1
+1 && 1; // => 1 (Logical and)
+0 && 1; // => 0
+0 || 1; // => 1 (Logical or)
+0 || 0; // => 0
+
+// Bitwise operators!
+~0x0F; // => 0xF0 (bitwise negation)
+0x0F & 0xF0; // => 0x00 (bitwise AND)
+0x0F | 0xF0; // => 0xFF (bitwise OR)
+0x04 ^ 0x0F; // => 0x0B (bitwise XOR)
+0x01 << 1; // => 0x02 (bitwise left shift (by 1))
+0x02 >> 1; // => 0x01 (bitwise right shift (by 1))
+
+///////////////////////////////////////
+// Control Structures
+///////////////////////////////////////
+
+if(0){
+  printf("I am never run\n");
+}else if(0){
+  printf("I am also never run\n");
+}else{
+  printf("I print\n");
+}
+
+// While loops exist
+int ii = 0;
+while(ii < 10){
+    printf("%d, ", ii++); // ii++ increments ii in-place, after using its value.
+} // => 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, before using its value
+// => 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");
+
+///////////////////////////////////////
+// Typecasting
+///////////////////////////////////////
+
+// Everything in C is stored somewhere in memory. You can change
+// the type of a variable to choose how to read its data
+
+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", (char) 257); // => 1 (Max char = 255)
+printf("%d\n", (short) 65537); // => 1 (Max short = 65535)
+
+///////////////////////////////////////
+// Pointers
+///////////////////////////////////////
+
+// You can retrieve the memory address of your variables,
+// then mess with them.
+
+int x = 0;
+printf("%p\n", &x); // Use & to retrieve the address of a variable
+// (%p formats a pointer)
+// => Prints some address in memory;
+
+int x_array[20]; // Arrays are a good way to allocate a contiguous block of memory
+int xx;
+for(xx=0; xx<20; xx++){
+    x_array[xx] = 20 - xx;
+} // Initialize x_array to 20, 19, 18,... 2, 1
+
+// Pointer types end with *
+int* x_ptr = x_array;
+// This works because arrays are pointers to their first element.
+
+// Put a * in front to de-reference a pointer and retrieve the value,
+// of the same type as the pointer, that the pointer is pointing at.
+printf("%d\n", *(x_ptr)); // => Prints 20
+printf("%d\n", x_array[0]); // => Prints 20
+
+// Pointers are incremented and decremented based on their type
+printf("%d\n", *(x_ptr + 1)); // => Prints 19
+printf("%d\n", x_array[1]); // => Prints 19
+
+// Array indexes are such a thin wrapper around pointer
+// arithmetic that the following works:
+printf("%d\n", 0[x_array]); // => Prints 20;
+printf("%d\n", 2[x_array]); // => Prints 18;
+
+// The above is equivalent to:
+printf("%d\n", *(0 + x_ptr));
+printf("%d\n", *(2 + x_ptr));
+
+// You can give a pointer a block of memory to use with malloc
+int* my_ptr = (int*) malloc(sizeof(int) * 20);
+for(xx=0; 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
+printf("%d\n", *(my_ptr + 21)); // => Prints who-knows-what?
+
+// When you're done with a malloc'd block, you need to free it
+free(my_ptr);
+
+// Strings can be char arrays, but are usually represented as char
+// pointers:
+char* my_str = "This is my very own string";
+
+printf("%d\n", *my_str); // 84 (The ascii value of 'T')
+
+function_1();
+} // end main function
+
+///////////////////////////////////////
+// Functions
+///////////////////////////////////////
+
+// Function declaration syntax:
+// <return type> <function name>(<args>)
+
+int add_two_ints(int x1, int x2){
+    return x1 + x2; // Use return a return a value
+}
+
+/*
+Pointers are passed-by-reference (duh), so functions
+can mutate their values.
+
+Example: in-place string reversal
+*/
+
+// A void function returns no value
+void str_reverse(char* str_in){
+    char tmp;
+    int ii=0, len = strlen(str_in); // Strlen is part of the c standard library
+    for(ii=0; ii<len/2; ii++){
+        tmp = str_in[ii];
+        str_in[ii] = str_in[len - ii - 1]; // ii-th char from end
+        str_in[len - ii - 1] = tmp;
+    }
+}
+
+/*
+char c[] = "This is a test.";
+str_reverse(c);
+printf("%s\n", c); // => ".tset a si sihT"
+*/
+
+///////////////////////////////////////
+// User-defined types and structs
+///////////////////////////////////////
+
+// Typedefs can be used to create type aliases
+typedef int my_type;
+my_type my_type_var = 0;
+
+// Structs are just collections of data
+struct rectangle {
+    int width;
+    int height;
+};
+
+
+void function_1(){
+
+    struct rectangle my_rec;
+
+    // Access struct members with .
+    my_rec.width = 10;
+    my_rec.height = 20;
+
+    // You can declare pointers to structs
+    struct rectangle* my_rec_ptr = &my_rec;
+
+    // Use dereferencing to set struct pointer members...
+    (*my_rec_ptr).width = 30;
+
+    // ... or use the -> shorthand
+    my_rec_ptr->height = 10; // Same as (*my_rec_ptr).height = 10;
+}
+
+// You can apply a typedef to a struct for convenience
+typedef struct rectangle rect;
+
+int area(rect r){
+    return r.width * r.height;
+}
+
+```
+
+## 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)
+
+Another good resource is [Learn C the hard way](http://c.learncodethehardway.org/book/)
+
+Other than that, Google is your friend.