| You are to write an interpreter for a simple computer. This computer uses a processor with a small number of machine instructions. Furthermore, it is equipped with 32 byte of memory, one 8-bit accumulator (accu) and a 5-bit program counter (pc). The memory contains data as well as code, which is the usual von Neumann architecture.
The program counter holds the address of the instruction to be executed next. Each instruction has a length of 1 byte - the highest 3 bits define the type of instruction and the lowest 5 bits define an optional operand which is always a memory address (xxxxx). For instructions that don't need an operand the lowest 5 bits have no meaning (-----). Here is a list of the machine instructions and their semantics:
000xxxxx STA x store the value of the accu into memory byte x
001xxxxx LDA x load the value of memory byte x into the accu
010xxxxx BEQ x if the value of the accu is 0 load the value x into the pc
011----- NOP no operation
100----- DEC subtract 1 from the accu
101----- INC add 1 to the accu
110xxxxx JMP x load the value x into the pc
111----- HLT terminate program
In the beginning, program counter and accumulator are set to 0. After fetching an instruction but before its execution, the program counter is incremented. You can assume that programs will terminate.
Input Specification
The input file contains several test cases. Each test case specifies the contents of the memory prior to execution of the program. Byte 0 through 31 are given on separate lines in binary representation. A byte is denoted by its highest-to-lowest bits. Input is terminated by EOF.
Output Specification
For each test case, output on a line the value of the accumulator on termination in binary representation, again highest bits first. |
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Sample Input
00111110
10100000
01010000
11100000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00111111
10000000
00000010
11000010
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
11111111
10001001
Sample Output
10000111
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很好的题，很容易错。
需要计算机组成原理的一点知识，没学过也能做。
指令译码，（将二进制转化为十进制并从中获得操作类型和立即数x）可以用位运算，
指令执行 pc,accu,立即数x都可以用int表示且是全局变量，memory用数组表示。
有很多注意的地方，
pc不能超过32;不能小于0.
accu不能超过256.不能小于0.
自己都没有注意到。
pc,accu,
posted on 2009-07-24 10:59
luis 阅读(295)
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