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Simple Computers
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 655 Accepted Submission(s): 260
Problem Description
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.
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
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
For each test case, output on a line the value of the accumulator on termination in binary representation, again highest bits first.
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
Source
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