diff --git a/src/r6502/instructions.rs b/src/r6502/instructions.rs
index a30e8d7..5a9d77e 100644
--- a/src/r6502/instructions.rs
+++ b/src/r6502/instructions.rs
@@ -361,22 +361,60 @@ impl Instructions
 
     pub fn STX(cpu: &mut R6502, bus: &mut dyn Bus)
     {
-
+        bus.write(cpu.working_addr, cpu.x);
     }
 
     pub fn LDX(cpu: &mut R6502, bus: &mut dyn Bus)
     {
+        let data = cpu.working_data as u8;
+        cpu.x = data;
 
+        if cpu.x == 0
+        {
+            cpu.set_flag(Flags::Z);
+        }
+
+        if cpu.x & 0x80 != 0
+        {
+            cpu.set_flag(Flags::N);
+        }
     }
 
     pub fn DEC(cpu: &mut R6502, bus: &mut dyn Bus)
     {
+        let dec_val = bus.read(cpu.working_addr) - 1;
+        bus.write(cpu.working_addr, dec_val);
+
+        cpu.clear_flag(Flags::Z);
+        if dec_val == 0
+        {
+            cpu.set_flag(Flags::Z);
+        }
+
+        cpu.clear_flag(Flags::N);
+        if dec_val & 0x80 > 0
+        {
+            cpu.set_flag(Flags::N);
+        }
 
     }
 
     pub fn INC(cpu: &mut R6502, bus: &mut dyn Bus)
     {
+        let dec_val = bus.read(cpu.working_addr) + 1;
+        bus.write(cpu.working_addr, dec_val);
+
+        cpu.clear_flag(Flags::Z);
+        if dec_val == 0
+        {
+            cpu.set_flag(Flags::Z);
+        }
 
+        cpu.clear_flag(Flags::N);
+        if dec_val & 0x80 > 0
+        {
+            cpu.set_flag(Flags::N);
+        }
     }
 
     ///////////////////////////////////////////////////////////
diff --git a/src/tests/instructions/mod.rs b/src/tests/instructions/mod.rs
index b768f41..6132451 100644
--- a/src/tests/instructions/mod.rs
+++ b/src/tests/instructions/mod.rs
@@ -337,4 +337,124 @@ fn ROR()
     assert_eq!(0, cpu.check_flag(Flags::Z), "Zero flag should not be set");
     assert_eq!(1, cpu.check_flag(Flags::C), "Carry flag should be set");
     assert_eq!(1, cpu.check_flag(Flags::N), "Negative flag should be set");
+}
+
+#[test]
+fn STX()
+{
+    let mut cpu = R6502::new();
+    let mut bus = RAMBus::new();
+
+    // program address
+    let addr = 0x0020 as u16;
+
+    // Set the program counter address
+    bus.write(0xFFFC, (addr & 0x00FF) as u8);  // low byte
+    bus.write(0xFFFD, ((addr & 0xFF00) >> 8) as u8);  // high byte
+
+
+    // STX $0A
+    bus.write(addr, 0x86); // STX - Zero Page mode
+    bus.write(addr + 1, 0x0A);  // Argument
+
+    // Restart cpu
+    cpu.reset(&mut bus);
+
+    // manually setup the cpu registers
+    cpu.debug_set_reg(Registers::X, 0x0F);
+
+    // Clock the cpu to run the program (Clock essentially runs one full instruction)
+    cpu.clock(&mut bus);
+
+    // Is 0x0F at memory address 0x0A?
+    assert_eq!(0x0F, bus.read(0x0A));
+
+}
+
+#[test]
+fn LDX() 
+{
+    let mut cpu = R6502::new();
+    let mut bus = RAMBus::new();
+
+    // program address
+    let addr = 0x0020 as u16;
+
+    // Set the program counter address
+    bus.write(0xFFFC, (addr & 0x00FF) as u8);  // low byte
+    bus.write(0xFFFD, ((addr & 0xFF00) >> 8) as u8);  // high byte
+
+    // Program to load 0x08 into the accumulator
+    bus.write(addr, 0xA2); // LDX - Immediate mode
+    bus.write(addr + 1, 0x08);  // Argument
+
+     // Restart cpu
+    cpu.reset(&mut bus);
+
+    // Clock the cpu to run the program (Clock essentially runs one full instruction)
+    cpu.clock(&mut bus);
+
+    // Is 0x08 in the X register?
+    assert_eq!(0x08, cpu.debug_get_reg(Registers::X));
+}
+
+#[test]
+fn DEC()
+{
+    let mut cpu = R6502::new();
+    let mut bus = RAMBus::new();
+
+    // program address
+    let addr = 0x0020 as u16;
+
+    // Set the program counter address
+    bus.write(0xFFFC, (addr & 0x00FF) as u8);  // low byte
+    bus.write(0xFFFD, ((addr & 0xFF00) >> 8) as u8);  // high byte
+
+    // put value to decrement into memory
+
+    bus.write(0x08, 0x10);
+
+    // Program to load 0x08 into the accumulator
+    bus.write(addr, 0xC6); // DEC - Zero Page
+    bus.write(addr + 1, 0x08);  // Argument
+
+     // Restart cpu
+    cpu.reset(&mut bus);
+
+    // Clock the cpu to run the program (Clock essentially runs one full instruction)
+    cpu.clock(&mut bus);
+
+    // Is 0x0F in memory at 0x08?
+    assert_eq!(0x0F, bus.read(0x08));
+}
+
+#[test]
+fn INC()
+{
+    let mut cpu = R6502::new();
+    let mut bus = RAMBus::new();
+
+    // program address
+    let addr = 0x0020 as u16;
+
+    // Set the program counter address
+    bus.write(0xFFFC, (addr & 0x00FF) as u8);  // low byte
+    bus.write(0xFFFD, ((addr & 0xFF00) >> 8) as u8);  // high byte
+
+    // Put value to decrement into memory
+    bus.write(0x08, 0x10);
+
+    // Program to load 0x08 into the accumulator
+    bus.write(addr, 0xE6); // INC - Zero Page
+    bus.write(addr + 1, 0x08);  // Argument
+
+     // Restart cpu
+    cpu.reset(&mut bus);
+
+    // Clock the cpu to run the program (Clock essentially runs one full instruction)
+    cpu.clock(&mut bus);
+
+    // Is 0x11 in memory at 0x08?
+    assert_eq!(0x11, bus.read(0x08));
 }
\ No newline at end of file
diff --git a/todo/todo.todo b/todo/todo.todo
index e4929c5..1820346 100644
--- a/todo/todo.todo
+++ b/todo/todo.todo
@@ -44,10 +44,10 @@ Instructions:
         ✔ 001	ROL @done(23-11-30 17:49)
         ✔ 010	LSR @done(23-11-30 18:12)
         ✔ 011	ROR @done(23-11-30 18:12)
-        ☐ 100	STX
-        ☐ 101	LDX
-        ☐ 110	DEC
-        ☐ 111	INC
+        ✔ 100	STX @done(24-01-08 13:46)
+        ✔ 101	LDX @done(24-01-08 14:21)
+        ✔ 110	DEC @done(24-01-08 15:59)
+        ✔ 111	INC @done(24-01-08 16:01)
 
     GROUP THREE:
         ☐ 001	BIT