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45 lines
2.5 KiB
Plaintext
45 lines
2.5 KiB
Plaintext
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Comments:
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R1 holds x, value to be found
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R2 holds head, the memory location of the first element
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R3 holds the number END = 16b'0000100000000000'=0x800 (for comparing, this is the end of the linked list)
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R4 holds the current element in the traversed list
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R5 holds the number 0xB (for jumping to the end)
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R6 holds the number 0x5 (for jumping back)
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A linked list pair is stored as men[N]=value and mem[N+1] = address of next element
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(0x0) LDA R1 ##MEMORY_LOCATION_OF_x## (loads the value to be found, x, into R1)
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(0x1) LDA R2 ##MEMORY_LOCATION_OF_head## (loads the address of the first element into R2)
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(0x2) LDA R3 ##MEMORY_LOCATION_OF_END## (loads a number (0x800) to R3 which is our definition of an end of a linked list)
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(0x3) LDA R5 ####MEMORY_LOCATION_CONTAINING_0xB## (loads a number (0xB) to R5 which is used for jumping to STP, when the element is found or no elements left)
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(0x4) LDA R6 ####MEMORY_LOCATION_CONTAINING_0x5## (loads a number (0x5) to R6 which is used for jumping to back, if current element is not the required element and there are still elements left)
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(0x5) LDR R4 R2 (loads R4 using data from the memory address which is the value in R4)
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(0x6) JC3 R5 R4 R1 (jumps to the end ('STP') if R4 (current element) is equal to R1 (required element))
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(0x7) ADO R2 (adds one to R2, which when completed contains the address of the address of next element in the linked list)
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(0x8) LDR R2 R2 (loads the address of the next element into R2, thus updating the current head)
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(0x9) JC3 R5 R2 R3 (jumps to the end ('STP') if R2 (current head) is equal to R3 (end of list)
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(0xA) JMP R6 (jumps to value stored in R4 () which repeats this process)
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(0xB) STP (program end)
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Example that can be used with the instruction generator program:
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LDA R1 0
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LDA R2 1
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LDA R3 2
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LDA R5 3
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LDA R6 4
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LDR R4 R2
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JC3 R5 R4 R1
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ADO R2
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LDR R2 R2
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JC3 R5 R2 R3
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JMP R6
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STP
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Requires setting the following data memory locations:
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Set location '0' to value of x;
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Set location '1' to value of head;
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Set location '2' to value of 0x800 (end of linked list)
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Set location '3' to value of 0xB (end of program, STP);
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Set location '4' to value of 0x5; (going back)
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Create a linked list that starts at 'head' memory location
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