| 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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很好的題，很容易錯(cuò)。
需要計(jì)算機(jī)組成原理的一點(diǎn)知識(shí)，沒學(xué)過也能做。
指令譯碼，（將二進(jìn)制轉(zhuǎn)化為十進(jìn)制并從中獲得操作類型和立即數(shù)x）可以用位運(yùn)算，
指令執(zhí)行 pc,accu,立即數(shù)x都可以用int表示且是全局變量，memory用數(shù)組表示。
有很多注意的地方，
pc不能超過32;不能小于0.
accu不能超過256.不能小于0.
自己都沒有注意到。
pc,accu,
posted on 2009-07-24 10:59
luis 閱讀(305)
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