Some docs improvements (#552)

* Some improvements

docs/basics/basicconcepts.md

@@ -1,33 +1,37 @@
 @page concepts Basic Concepts
-See terminology for explanations of terms.  
+See [terminology](terminology.html) for explanations of terms.  
 
-## Addresses
-Computers use addresses to jump through code. This works similar to finding a house using its address. Except, that reaching the house is nearly instantaneous and it only contains more instructions and jumps or some data such as a texture or a text string. Also, when finished with the house, you travel back to the previous destination which may have some left-over instructions or more jumps. You can imagine this quickly becoming a spaghetti monster jumping all over the place.
+# Addresses
+Computers use addresses to jump through code. This works similar to a house number.
+* A house contains a series of instructions or some data (ex. a texture).
+* A house can contain more jumps.
+* When business in a house completes, the computer jumps to the last house it was in.
+* The program execution completes when there are no more branches left.
+* Programs run in a big infinite loop so it cannot run out of branches.
+* A program may be imagined as a big spaghetti monster.
+* Note that n64 only runs one command/thread at a time.
 
-A typical N64 address: `0x8029E158`
+A typical N64 address: `0x80160158`
 
 In an N64 program, addresses begin at `0x80000000`. As you create code, data, and the like, the compiler will add onto this base number and assign variables to an address.
 ```
-s32 a_value = 2; // Note that a_value can be any name: fox, pig, siodfj, etc.
-s32 b_value = 7;
+s32 a = 2; // 0x80000004
+s32 b = 7; // 0x80000008
+s32 c = 5; // 0x8000000C
+s32 d = 1; // 0x80000010
+s32 e = 3; // 0x80000014
 ```
-Might compile a_value to `0x80000004` and b_value to `0x80000008`. At anytime if you manually wrote:
+Replacing a variable with a hard-coded address grabs the value at that address.
 ```
 print(0x80000004); // or
-print(a_value);
-```
-Both would output `2`. This allows some trickery. Such as pointer math: `print(0x800000004 + 0x80000004)` would output `7`.
-
-Addresses generally count up by fours: `0x4, 0x8, 0xC, 0x10, 0x14, etc.`
-
-It does not when working with s8 and s16 integer types. An s32 or int always takes up eight digits: `00000001`
-```
-s32 a = 1;
 print(a);
 ```
-Will output `1` but if you opened the program in a hexadecimal file you will notice that its written to disc as `0x00000001`
+Both would output `2`. This allows some trickery. Such as pointer math: `print(0x800000004 + 0x80000004)` would output `7`.
+Pointers may be similarily influenced: `&a + 4` results in `0x800000008` thus printing the value at `b`.
 
-An s16 looks like: `0x0001` an s8 looks like: `0x01`.
+The compiler may `align` or offset variables to certain addresses. Generally, certain types of data is aligned to 0x10.
+
+If `c` were placed in a new file, the compiler would place `c` at `0x80000010` and `e` would be placed at `0x80000020`.
 
 Data can take up tonnes of space:
 ```
@@ -35,18 +39,42 @@ Texture a_texture[] = {
   0x01, 0x0A, 0xAA, 0x34, 0x23, // Imagine five-hundred lines of this
 };
 ```
-The address of this could extend from `0x80000100` to `0x800000534`. However, you would not see `0x80000533`. The compiler generally aligns objects to 4, 8, 0xC, or 0x10 (Note that files are generally aligned to 0x10). With the exception being when you're working with s16 and s8. If you have:
+The address of this could extend from `0x80000100` to `0x800000534`. However, you would not see data begin at `0x80000533`. The compiler generally aligns objects to 4, 8, 0xC, or 0x10. With the exception being when you're working with s16 and s8. If you have:
 ```
-s16 a = 3;
-s32 b = 5;
+s16 a = 3; // Value compiled to 0x0003
+s32 b = 5; // Value compiled to 0x00000005
 ```
-You might expect to see this: `000300000005` or `0x0003 0x00000005` But actually, it will be this:
+In a hexadecimal editor you may expect to see this: `000300000005` or `0x0003 0x00000005` But actually, it will be this:
 ```
 0003000000000005 or 0x0003 0x0000 0x00000005
 ```
-This is called alignment. The compiler *aligned* `b` to the next 'major' address. Of course, if you program two s16's then the blank `0x0000` will be used. The max size of an s8 is 0xFF (255). Trying to write a number higher than 255 to an s8 type may crash the program as it might try to write onto the next variable.  
+The compiler aligned `b` to the nearest 0x4. If there were two s16's then the blank `0x0000` will be used.
 
-### Code
+# How Errors Happen
+The maximum value of an s8 (0x00) is 0xFF or 255. `0xFF + 1 = 0x100` imagine this scenario:
+```
+s8 a = 1;
+s8 b = 2;
+s8 c = 3;
+s8 d = 255;
+f32 e = 5.0f;
+```
+If `d` was set to 0x100, the final `0` would be written to the first bit of `e`. This could result in an invalid float value or perhaps flipping the signedness of an s32 (from negative to positive and vice-versa).
+
+Issues such as this could result in glitches or crashes. Once humble math calculating to immeasurable values.
+
+## Array Overflows
+In the below example, my_func writes a value at the fifth index which does not exist. This results in writing 5.0f into the next variable lkely resulting in a crash. Array overflows may be easy to miss in complex programs and sometimes only crash on rare occasion.
+```
+f32 myArray[4] = {8.0f, 3.0f, 9.0f, 1.0f};
+
+void my_func(index) {
+    myArray[index] = 5.0f;
+}
+my_func(5);
+```
+
+# Code
 Code contains addresses too. Lets take a look at some example assembly:
 ```
 glabel entry_point
@@ -65,13 +93,13 @@ The `lui, addiu, ori, etc.` are just representations of the machine-code. For ex
 `op-code, parameters`
 0x3C is the op-code (lui or load-upper-immediate) this command loads an address. The `08` tells the CPU to use the register `t0` and the `0x800F` is the first-half of the address to load. So, in the register t0 (which is the size of an int: 0x00000000) the value `0x800F0000` is written.
 
-Note that one machine-code command is the size of an int/s32/word. How do we load an address (which is the size of an int). There isn't enough room when you include the op-code and register: `0x3C08800F6990`. That no worky. So we have to do this with two commands called a hi and a lo:
+Note that one machine-code command is the size of an int/s32/word. How do we load an address (which is the size of an int). There isn't enough room when you include the op-code and register: `0x3C08800F6990`. That no worky. As such, loading data at an address requires two commands. The first half of the address is called a hi and the second half is called a lo:
 ```
 /* 001008 80000408 25086910 */  addiu $t0, %lo(_mainSegmentEnd) # addiu $t0, $t0, 0x6910
 ```
 Now, we're going to *add* the *offset*: `t0: 0x800F0000 + 0x6910 = 0x800F6910`.
-If you run the game and use a memory viewer at this location. You will quickly realize this region of data (it's actually .bss but lets not get into that), is the controller data. The data alters to reflect which controller buttons are pressed. So if I just wanted to read one of these values, the assembly will do two commands to put the address in the register. Then another command can read the address in that register to receive the value at that location. This value can be compared to see if the button is active. Ex. zero might mean not pressed, whereas one might mean pressed.
+If you run the game and use a memory viewer at this location. You will quickly realize this region of data (it's actually .bss but lets not get into that), is the controller data. The data alters to reflect which controller buttons are pressed. So if I just wanted to read one of these values, the cpu will run two commands to put the address into the register. Then another command can read the address in that register to receive the value at that location. This value can be compared to see if the button is active. Ex. zero might mean not pressed, whereas one might mean pressed.
 
-Now, earlier it was mentioned that code contains addresses. If I wanted to, I could do this: `Jump to: 0x80000410`. Which would make the CPU start running code at that location. Or I could read the value that exists there: `0x2129FFF8`. Not sure what I might do with that number, but it does act like a normal number. In decimal it is: `556,400,632`. I could add and subtract to it (Which would likely crash the game if it tried to run that command after). Now, jumping to any code address in the middle of a function would almost certainly crash the game or result in strange behaviour. The purpose of this explanation is really to show that everything is just a bunch of numbers or values, represented by an address. Even code itself.
+Now, earlier it was mentioned that code contains addresses. If I wanted to, I could do this: `Jump to: 0x80000410`. Which would make the CPU start running code at that location. Or I could read the value that exists there: `0x2129FFF8`. Not sure what I might do with that number, but it does act like a normal number. In decimal it is: `556,400,632`. I could add and subtract to it (Which would likely crash the game if it tried to run that command after). Now, jumping to any code address in the middle of a function would almost certainly crash the game or result in strange behaviour. The purpose of this explanation is really to show that everything is just a bunch of numbers or values, represented by an address. Even the code itself.
 
 For a more refined explanation of addresses and pointers its suggested to use the Googles. However, this explanation was written with the N64 in-mind.