add README

Author: Enayaaa

README.md

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+# ChAcc Assembler
+I wanted to write assembly to test on our processor made in VHDL and needed an assembler.
+It was also an exercise to see how functional/combinatorial parsing worked in haskell (see Parser.hs)
+
+## Processor description
+The ChAcc processor, based on the lab processor of HY-120 course in the institute of Computer Science
+in FORTH, Greece, is a simple and slow processor which can run various programs. It is an 8-bit processor,
+i.e., the processor executes operations on 8-bit data but executes instructions
+which are 12-bit long. ChAcc makes use of the accumulator architecture, which has a special register, called
+Accumulator (ACC). The register is so named because it can perform consecutive operations (e.g., additions)
+and accumulate the result. ACC keeps the result of the most recent operation. Almost every instruction
+works on ACC and the content of a memory location.
+
+## Build
+    ghc --make Main.hs
+
+## Run
+    ./Main valid.asm