在这里，我们有一条11位指令，其中前2位用于表示寻址模式，后3位用于操作码，后6位用于两个操作数，每个3位。
我们将使用四种不同的寻址模式执行此11位指令：
- 直接模式：在此模式下，在指令中指定两个操作数的地址。我们可以直接从内存地址接收实际数据。
- 间接模式：在此模式下，指令中提到的地址指向操作数的有效地址。
- 立即模式：在此模式下，实际数据在指令本身中提及。
- 寄存器模式：在此模式下，指令包含包含实际数据的寄存器的地址。
我们将使用前2位以这种方式表示四种不同的寻址模式：
For direct mode- 00
For indirect mode- 01
For immediate mode- 10
For register mode- 11
接下来的3位代表操作码，因此我们最多可以使用8种不同的操作。我们将定义6个操作，而其他两个将以这种方式保留给将来使用：
000- Do nothing
001- Addition
010- Subtraction
011- Multiplication
100-Division
101-Transfer operand2 to operand1
110-Reserve for future
111-Reserve for future
接下来的3位用于操作数1，最后3位用于操作数2，因此在立即模式下，操作数的值范围为0到7。
对于直接，间接和寄存器模式，我们需要定义一个存储器阵列和一个寄存器阵列。由于我们只有3位代表地址，因此这些数组中的最大元素数将为8。
memory=[2,15,40,25,7,36,64,19]
register=[17,20,43,52,None,None,None,None]
此处，存储器包含8个数据，而寄存器包含4个数据。上面讨论的概念将以下列方式工作：
Input: 01001000100
Here, from left to right
Mode-01- Indirect mode
Opcode-001- Addition
Operand1-000- 0
Operand2 – 100- 4
As it is the indirect mode, so these operands gives the addresses of the effective address of the data.
Means, the effective addresses are present in the memory location 0 and 4 , which are 2 and 7.
And the actual data is present in the memory location 2 and 7 which are 40 and 19.
So, the result will be the addition of 40 and 19.
Output: 59
例子：
Python
memory=[2,15,40,25,7,36,64,19]
register=[17,20,43,52,None,None,None,None]
#This function execute the instruction and print the result.
def execute(st):
mode=st[:2]
opcode=st[2:5]
operand1=st[5:8]
operand2=st[8:]
print()
print("Instruction mode:",mode)
print("Opcode:",opcode)
print("operand1:",operand1)
print("operand2:",operand2)
#For direct mode
if mode=='00':
idx1=int(operand1,2)
idx2=int(operand2,2)
if opcode=='000':
print("Do nothing")
elif opcode=='001':
print("RESULT")
print(memory[idx1]+memory[idx2])
elif opcode=='010':
print("RESULT")
print(memory[idx1]-memory[idx2])
elif opcode=='011':
print("RESULT")
print(memory[idx1]*memory[idx2])
elif opcode=='100':
print("RESULT")
print(memory[idx1]/memory[idx2])
elif opcode=='101':
print("RESULT")
print("operand1=:")
print(int(operand2,2))
else:
print("Reserve For Future")
#For indirect mode
elif mode=='01':
idx1=int(operand1,2)
idx2=int(operand2,2)
idx1=memory[idx1]
idx2=memory[idx2]
if opcode=='000':
print("Do nothing")
elif opcode=='001':
print("RESULT")
print(memory[idx1]+memory[idx2])
elif opcode=='010':
print("RESULT")
print(memory[idx1]-memory[idx2])
elif opcode=='011':
print("RESULT")
print(memory[idx1]*memory[idx2])
elif opcode=='100':
print("RESULT")
print(memory[idx1]/memory[idx2])
elif opcode=='101':
print("RESULT")
print("operand1=:")
print(int(operand2,2))
else:
print("Reserve For Future")
#For immediate mode
elif mode=='10':
idx1=int(operand1,2)
idx2=int(operand2,2)
if opcode=='000':
print("Do nothing")
elif opcode=='001':
print("RESULT")
print(idx1+idx2)
elif opcode=='010':
print("RESULT")
print(idx1-idx2)
elif opcode=='011':
print("RESULT")
print(idx1*idx2)
elif opcode=='100':
print("RESULT")
print(idx1/idx2)
elif opcode=='101':
print("RESULT")
print("operand1=:")
print(int(operand2,2))
else:
print("Reserve For Future")
#For register mode
else:
idx1=int(operand1,2)
idx2=int(operand2,2)
if idx1>3 or idx2>3:
print("Invalid")
exit()
if opcode=='000':
print("Do nothing")
elif opcode=='001':
print("RESULT")
print(register[idx1]+register[idx2])
elif opcode=='010':
print("RESULT")
print(register[idx1]-register[idx2])
elif opcode=='011':
print("RESULT")
print(register[idx1]*register[idx2])
elif opcode=='100':
print("RESULT")
print(register[idx1]/register[idx2])
elif opcode=='101':
print("RESULT")
print("operand1=:")
print(int(operand2,2))
else:
print("Reserve For Future")
#driver code
st="00001000001"
execute(st);
st="01001000100"
execute(st);
st="10001000001"
execute(st);
st="11001000001"
execute(st);输出：
Instruction mode: 00
Opcode: 001
operand1: 000
operand2: 001
RESULT
17
Instruction mode: 01
Opcode: 001
operand1: 000
operand2: 100
RESULT
59
Instruction mode: 10
Opcode: 001
operand1: 000
operand2: 001
RESULT
1
Instruction mode: 11
Opcode: 001
operand1: 000
operand2: 001
RESULT
37