Added registers.md

registers.md

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+
+# Intel
+
+  General 32-bit registers:
+
+  __EAX__ - Accumulator Register
+  __EBX__ - Base Register
+  __ECX__ - Counter Register
+  __EDX__ - Data Register
+  __ESI__ - Source Index
+  __EDI__ - Destination Index
+  __EBP__ - Base Pointer
+  __ESP__ - Stack Pointer
+
+## Descriptions
+
+  __EAX__ - All major calculations take place in EAX,
+  making it similar to a dedicated accumulator register.
+
+  __EDX__ - The data register is the an extension to the accumulator.
+  It is most useful for storing data related to the accumulator's current calculation.
+
+  __ECX__ - Like the variable i in high-level languages,
+  the count register is the universal loop counter.
+
+  __EDI__ - Every loop must store its result somewhere, and the
+  destination index points to that place. With a single-byte STOS
+  instruction to write data out of the accumulator, this register
+  makes data operations much more size-efficient.
+
+  __ESI__ - In loops that process data, the source index holds
+  the location of the input data stream. Like the destination index,
+  EDI had a convenient one-byte instruction for loading data out of
+  memory into the accumulator.
+
+  __ESP__ - ESP is the sacred stack pointer. With the important PUSH,
+  POP, CALL, and RET instructions requiring it's value, there is never
+  a good reason to use the stack pointer for anything else.
+
+  __EBP__ - In functions that store parameters or variables on the
+  stack, the base pointer holds the location of the current stack
+  frame. In other situations, however, EBP is a free data-storage register.
+
+  __EBX__ - In 16-bit mode, the base register was useful as a pointer.
+  Now it is completely free for extra storage space.
+