想用Labels来简化Little Man Computer Program BubbleSort

Want to use Labels to simplify Little Man Computer Program BubbleSort

此代码是一个 Little Man Computer 程序,它对输入、输出进行冒泡排序,并自行排序然后重复。这是程序,但我想对所有常量、变量和分支将到达的分支目标位置使用标签,以帮助简化代码并使其更具可读性。我不确定使用什么标签名称来提高可维护性。不需要数字代码。只有行号、标签、助记词数据和注释。

000 IN      9001      // input count
001 STO 090 3090 // store count
002 LDA 096 5096 // STO
003 ADD 095 1095 // Determine first location
004 STO 011 3011 // Overwrite STO instruction for list
005 ADD 090 1090
006 STO 092 3092 // Store STO + LOC + Count to determine end
007 LDA 011 5013 // Load manipulated instruction (using as counter)
008 SUB 092 2092 //
009 BRZ 016 7016 // If last count, go to END INPUT LIST
010 IN 9001   
011 DAT 0        // manipulated instruction (store input in list)
012 LDA 011 5011
013 ADD 098 1098 // increment store instruction (to next list location)
014 STO 011 3011 // Update STO instruction
015 BR 007 6007 // GOTO INPUT LIST LOOP
016 LDA 098 5098
017 SUB 090 2090 // 1 – count
018 BRP 061 8061 // GO TO END I LOOP
019 LDA 099 5099
020 STO 092 3092 // set I to zero (0)
021 LDA 090 5090
022 SUB 098 2098 // COUNT - 1
023 SUB 092 1092 // COUNT -1 – I
024 BRZ 061 7061 // if(I == count - 1) GOTO END I LOOP
025 LDA 090 5090
026 SUB 098 2098
027 STO 093 3093 // J = Count – 1
028 LDA 092 5092 // I
029 SUB 093 2093 // I - J
030 BRP 057 8057 // If I == j, then GO END J LOOP
031 LDA 097 5097 // load LDA instruction numeric code
032 ADD 095 1095 // set to LDA 500
033 ADD 093 1093 // set to LDA [500 + j] or A[j]
034 STO 039 3039 // reset instruction
035 SUB 098 2098 // set to LDA [500 + j – 1] or A[j-1]
036 STO 037 3037 // reset instruction
037 DAT 0 // load A[j-1] (instruction is manipulated)
038 STO 088 3088
039 DAT 0 // load A[j] (instruction is manipulated)
040 STO 089 3089
041 SUB 088 2088 // A[j] – A[j-1] (swap if not positive)
042 BRP 053 8053 // GOTO DECREMENT J
043 LDA 096 5096 // load STO instruction code
044 ADD 095 1095 // set to STO 500
045 ADD 093 1093 // set to STO [500 + j]
046 STO 052 3052 // reset instruction
047 SUB 098 2098 // set to STO [500 + j – 1]
048 STO 050 3050 // reset instruction
049 LDA 089 5089 // load A[j]
050 DAT 0 // Store in A[j-1] (instruction is manipulated)
051 LDA 088 5088 // load A[j-1]
052 DAT 0 // Store in A[j] (instruction is manipulated)
053 LDA 093 5093
054 SUB 098 2098
055 STO 093 3093 // J = J – 1
056 BR 028 6028 // GOTO START J LOOP
057 LDA 092 5092
058 ADD 098 1098
059 STO 092 3092 // I = I + 1
060 BR 021 6021 // GOTO START I LOOP
061 LDA 090 5090 // Count
062 OUT 9002
063 LDA 097 5097
064 ADD 095 1095 // LDA + LOC
065 STO 071 3071 // set up instruction
066 ADD 090 1090 // LDA + LOC + Count
067 STO 092 3092 // store unreachable instruction
068 LDA 071 5071 // load manipulated instruction (used as counter)
069 SUB 092 2092
070 BRZ 077 7077 // GOTO END OUTPUT LOOP
071 DAT 0 // manipulated output
072 OUT 9002
073 LDA 071 5071
074 ADD 098 1098
075 STO 071 3071 // increment manipulated instruction
076 BR 068 6028 // GOTO OUTPUT LIST LOOP
077 BR 0 6000 // Branch to top of loop (embedded)
078 HLT 0 // (Should never hit this instruction)
088 DAT 0 // A[j-1] value (also used for swapping)
089 DAT 0 // A[j] value (also used for swapping)
090 DAT 0 // count variable (input and output)
091 DAT 0 // unused
092 DAT 0 // ‘I’ counter
093 DAT 0 // ‘j’ counter
094 DAT 0 // unused
095 DAT 500 // initial list location
096 DAT 3000 // STO instruction
097 DAT 5000 // LDA instruction
098 DAT 1 // one (constant)
099 DAT 0 // zero (constant)

只需使用评论作为标签的灵感。不是任何操作目标的行可以没有标签。例如:

start          IN                  // input count
               STO count           // store count
               LDA stoInstruction  // STO
               ADD location        // Determine first location
               STO storeInput      // Overwrite STO instruction for list
               ADD count 
               STO i               // Store STO + LOC + Count to determine end
loopInput      LDA storeInput      // Load manipulated instruction (using as counter)
               SUB i               //
               BRZ exitInputLoop   // If last count, go to END INPUT LIST
               IN    
storeInput     DAT                 // manipulated instruction (store input in list)
               LDA storeInput 
               ADD one             // increment store instruction (to next list location)
               STO storeInput      // Update STO instruction
               BR loopInput        // GOTO INPUT LIST LOOP
exitInputLoop  LDA one 
               SUB count           // 1 – count
               BRP exitLoopI       // GO TO END I LOOP
               LDA zero 
               STO i               // set I to zero (0)
loopI          LDA count 
               SUB one             // COUNT - 1
               SUB i               // COUNT -1 – I
               BRZ exitLoopI       // if(I == count - 1) GOTO END I LOOP
               LDA count 
               SUB one 
               STO j               // J = Count – 1
loopJ          LDA i               // I
               SUB j               // I - J
               BRP exitLoopJ       // If I == j, then GO END J LOOP
               LDA ldaInstruction  // load LDA instruction numeric code
               ADD location        // set to LDA 500
               ADD j               // set to LDA [500 + j] or A[j]
               STO loadCurrent     // reset instruction
               SUB one             // set to LDA [500 + j – 1] or A[j-1]
               STO loadPrevious    // reset instruction
loadPrevious   DAT                 // load A[j-1] (instruction is manipulated)
               STO previous 
loadCurrent    DAT                 // load A[j] (instruction is manipulated)
               STO current 
               SUB previous        // A[j] – A[j-1] (swap if not positive)
               BRP decrementJ      // GOTO DECREMENT J
               LDA stoInstruction  // load STO instruction code
               ADD location        // set to STO 500
               ADD j               // set to STO [500 + j]
               STO storeCurrent    // reset instruction
               SUB one             // set to STO [500 + j – 1]
               STO storePrevious   // reset instruction
               LDA current         // load A[j]
storePrevious  DAT                 // Store in A[j-1] (instruction is manipulated)
               LDA previous        // load A[j-1]
storeCurrent   DAT                 // Store in A[j] (instruction is manipulated)
decrementJ     LDA j 
               SUB one 
               STO j               // J = J – 1
               BR loopJ            // GOTO START J LOOP
exitLoopJ      LDA i 
               ADD one 
               STO i               // I = I + 1
               BR loopI            // GOTO START I LOOP
exitLoopI      LDA count           // Count
               OUT 
               LDA ldaInstruction
               ADD location        // LDA + LOC
               STO instruction     // set up instruction
               ADD count           // LDA + LOC + Count
               STO i               // store unreachable instruction
loopOutput     LDA instruction     // load manipulated instruction (used as counter)
               SUB i 
               BRZ exitLoopOutput  // GOTO END OUTPUT LOOP
instruction    DAT                 // manipulated output
               OUT 
               LDA instruction 
               ADD one 
               STO instruction     // increment manipulated instruction
               BR loopOutput       // GOTO OUTPUT LIST LOOP
exitLoopOutput BR start            // Branch to top of loop (embedded)
               HLT                 // (Should never hit this instruction)

previous       DAT                 // A[j-1] value (also used for swapping)
current        DAT                 // A[j] value (also used for swapping)
count          DAT                 // count variable (input and output)
               DAT                 // unused
i              DAT                 // ‘I’ counter
j              DAT                 // ‘j’ counter
               DAT                 // unused
location       DAT  500            // initial list location
stoInstruction DAT 3000            // STO instruction
ldaInstruction DAT 5000            // LDA instruction
one            DAT    1            // one (constant)
zero           DAT    0            // zero (constant)

备注:

  • 这个 LMC 是原始 LMC 的一个变体,它有 3 位数字,而你似乎正在使用一个使用 4 位数字的 LMC。

  • 代码不是很简洁:用了98个邮箱,不包括输入数据需要的存储空间。它可以用更少的东西来完成。在使用 75 个邮箱的 中查找实例。

  • 你写的是需要行号,但是当你使用标签时,行号(即邮箱号)变得无关紧要:LMC-assembler 可以在汇编期间分配它们。

运行 在标准的 100 邮箱 LMC 上

根据您的意见,我在这里提供了一个适用于标准 LMC 的代码版本。这意味着没有太多 space 留给实际输入数据:只有 11 个邮箱留给数据。

我必须替换以下部分:

location       DAT  500            // initial list location
stoInstruction DAT 3000            // STO instruction
ldaInstruction DAT 5000            // LDA instruction

...有了这个:

location       DAT list            // initial list location
stoInstruction DAT 300             // STO instruction
ldaInstruction DAT 500             // LDA instruction
list           DAT                 // start of the list

这是必要的,因为在标准 LMC 中:

  • 操作码是3位,不是4位;
  • 邮箱地址是 2 位数字,而不是 3 位(因此 500 是不可接受的);
  • 最好只使用下一个可用地址作为列表的位置,而不是硬编码的邮箱地址。

我还删除了定义未使用邮箱的两行。

最后,我会用 BRP 指令更改两个 BRZ 指令,因为理论上无法保证前一个 SUB 给出负结果时累加器的值是多少.在那种情况下,不能依赖累加器的值(因为它只能有非负值——参见维基百科)。因此,对未定义的值执行 BRZ 是有风险的。 BRP 是一条安全指令,因为它检查标志——而不是累加器。

#input: 3 44 22 99
start          IN                  // input count
               STO count           // store count
               LDA stoInstruction  // STO
               ADD location        // Determine first location
               STO storeInput      // Overwrite STO instruction for list
               ADD count 
               STO i               // Store STO + LOC + Count to determine end
loopInput      LDA storeInput      // Load manipulated instruction (using as counter)
               SUB i               //
               BRP exitInputLoop   // If last count, go to END INPUT LIST
               IN    
storeInput     DAT                 // manipulated instruction (store input in list)
               LDA storeInput 
               ADD one             // increment store instruction (to next list location)
               STO storeInput      // Update STO instruction
               BR loopInput        // GOTO INPUT LIST LOOP
exitInputLoop  LDA one 
               SUB count           // 1 – count
               BRP exitLoopI       // GO TO END I LOOP
               LDA zero 
               STO i               // set I to zero (0)
loopI          LDA count 
               SUB one             // COUNT - 1
               SUB i               // COUNT -1 – I
               BRZ exitLoopI       // if(I == count - 1) GOTO END I LOOP
               LDA count 
               SUB one 
               STO j               // J = Count – 1
loopJ          LDA i               // I
               SUB j               // I - J
               BRP exitLoopJ       // If I == j, then GO END J LOOP
               LDA ldaInstruction  // load LDA instruction numeric code
               ADD location        // set to LDA 500
               ADD j               // set to LDA [500 + j] or A[j]
               STO loadCurrent     // reset instruction
               SUB one             // set to LDA [500 + j – 1] or A[j-1]
               STO loadPrevious    // reset instruction
loadPrevious   DAT                 // load A[j-1] (instruction is manipulated)
               STO previous 
loadCurrent    DAT                 // load A[j] (instruction is manipulated)
               STO current 
               SUB previous        // A[j] – A[j-1] (swap if not positive)
               BRP decrementJ      // GOTO DECREMENT J
               LDA stoInstruction  // load STO instruction code
               ADD location        // set to STO 500
               ADD j               // set to STO [500 + j]
               STO storeCurrent    // reset instruction
               SUB one             // set to STO [500 + j – 1]
               STO storePrevious   // reset instruction
               LDA current         // load A[j]
storePrevious  DAT                 // Store in A[j-1] (instruction is manipulated)
               LDA previous        // load A[j-1]
storeCurrent   DAT                 // Store in A[j] (instruction is manipulated)
decrementJ     LDA j 
               SUB one 
               STO j               // J = J – 1
               BR loopJ            // GOTO START J LOOP
exitLoopJ      LDA i 
               ADD one 
               STO i               // I = I + 1
               BR loopI            // GOTO START I LOOP
exitLoopI      LDA count           // Count
               OUT 
               LDA ldaInstruction
               ADD location        // LDA + LOC
               STO instruction     // set up instruction
               ADD count           // LDA + LOC + Count
               STO i               // store unreachable instruction
loopOutput     LDA instruction     // load manipulated instruction (used as counter)
               SUB i 
               BRP exitLoopOutput  // GOTO END OUTPUT LOOP
instruction    DAT                 // manipulated output
               OUT 
               LDA instruction 
               ADD one 
               STO instruction     // increment manipulated instruction
               BR loopOutput       // GOTO OUTPUT LIST LOOP
exitLoopOutput BR start            // Branch to top of loop (embedded)
               HLT                 // (Should never hit this instruction)

previous       DAT                 // A[j-1] value (also used for swapping)
current        DAT                 // A[j] value (also used for swapping)
count          DAT                 // count variable (input and output)
i              DAT                 // ‘I’ counter
j              DAT                 // ‘j’ counter
location       DAT list            // initial list location
stoInstruction DAT 300             // STO instruction
ldaInstruction DAT 500             // LDA instruction
one            DAT   1             // one (constant)
zero           DAT   0             // zero (constant)
list           DAT

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