diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..1e08526
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "burritos"
+version = "0.1.0"
diff --git a/src/decode.rs b/src/decode.rs
new file mode 100644
index 0000000..80ac041
--- /dev/null
+++ b/src/decode.rs
@@ -0,0 +1,90 @@
+pub struct Instruction {
+    pub value : u64,
+
+    pub opcode : u8, 
+    pub rs1 : u8, 
+    pub rs2 : u8, 
+    pub rs3 : u8, 
+    pub rd : u8, 
+    pub funct7 : u8, 
+    pub funct7_smaller : u8, 
+    pub funct3 : u8, 
+    pub shamt : u8,
+
+    pub imm12_I : u16,
+    pub imm12_S : u16,
+
+    pub imm12_I_signed : i16, 
+    pub imm12_S_signed : i16, 
+    pub imm13 : i16, 
+    pub imm13_signed : i16,
+
+    pub imm31_12 : u32, 
+    pub imm21_1 : u32,
+
+    pub imm31_12_signed : i32, 
+    pub imm21_1_signed : i32,
+}
+
+pub fn decode(val : u64) -> Instruction {
+
+    let value = val;
+
+    let opcode          = (val & 0x7f) as u8;
+    let rs1             = ((val >> 15) & 0x1f) as u8;
+    let rs2             = ((val >> 20) & 0x1f) as u8;
+    let rs3             = ((val >> 27) & 0x1f) as u8;
+    let rd              = ((val >> 7) & 0x1f) as u8;
+    let funct7          = ((val >> 25) & 0x7f) as u8;
+    let funct7_smaller  = (funct7 & 0x3e) as u8;
+    
+    let funct3          = ((val >> 12) & 0x7) as u8;
+    let imm12_I         = ((val >> 20) & 0xfff) as u16;
+    let imm12_S         = (((val >> 20) & 0xfe0) + ((val >> 7) & 0x1f)) as u16;
+    
+    let imm12_I_signed  = if imm12_I >= 2048 { imm12_I - 4096 } else { imm12_I } as i16;
+    let imm12_S_signed  = if imm12_S >= 2048 { imm12_S - 4096 } else { imm12_S } as i16;
+    
+    let imm13           = (((val >> 19) & 0x1000) + ((val >> 20) & 0x7e0) +
+                        ((val >> 7) & 0x1e) + ((val << 4) & 0x800)) as i16;
+    let imm13_signed    = if imm13 >= 4096 { imm13 - 8192 } else { imm13 } as i16;
+    
+    let imm31_12        = (val & 0xfffff000) as u32;
+    let imm31_12_signed = imm31_12 as i32;
+    
+    let imm21_1         = ((val & 0xff000) + ((val >> 9) & 0x800) +
+                        ((val >> 20) & 0x7fe) + ((val >> 11) & 0x100000)) as u32;
+    let imm21_1_signed  = if imm21_1 >= 1048576 { imm21_1 - 2097152 } else { imm21_1 } as i32;
+    
+    let shamt           = ((val >> 20) & 0x3f) as u8;
+    
+    Instruction {
+        value : value,
+
+        opcode : opcode,
+        rs1 : rs1,
+        rs2 : rs2,
+        rs3 : rs3,
+        rd  : rd,
+        funct7 : funct7,
+        funct7_smaller : funct7_smaller,
+    
+        funct3 : funct3,
+        imm12_I : imm12_I,
+        imm12_S : imm12_S,
+    
+        imm12_I_signed : imm12_I_signed,
+        imm12_S_signed : imm12_S_signed,
+    
+        imm13 : imm13,
+        imm13_signed : imm13_signed,
+    
+        imm31_12 : imm31_12,
+        imm31_12_signed : imm31_12_signed,
+    
+        imm21_1 : imm21_1,
+        imm21_1_signed : imm21_1_signed,
+    
+        shamt : shamt
+    }
+}
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..16cda16 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,6 @@
+mod decode;
+
 fn main() {
-    println!("Hello, world!");
+    let instr = decode::decode(98);
+    println!("Hello, world! opcode : {}", instr.opcode);
 }