Print all digits of a given number in LMC

Question

I need to print all digits of a given number in LMC. I tried with this code who gives me the last digit but I don't know how to keep going with the other digits.

    INP
L0  STA R0
    SUB R1
    BRP L0
    LDA R0
    OUT
    HLT
R0  DAT 000
R1  DAT 010

Answer 1

The code you have will output the least significant digit. To produce the other two digits (knowing that the LMC is limited to 3 digit numbers), first subtract 100 repeatedly and count how many times you could do that: this would be the first digit to output. Then subtract 10 repeatedly and count... and finally output the remainder.

For the repeated subtraction you need a loop. You could consider using self modifying code in order to reuse the same loop for subtracting 100 and later on for subtracting 10. But you might as well write a separate loop for each of these two cases:

#input:321
          INP
          STA input
          LDA zero   ; prepare for finding first digit
          BRA enter1

loop1     STA input
          LDA digit  ; increment digit
          ADD one
enter1    STA digit
          LDA input
          SUB hundred ; output number of 100s
          BRP loop1
          LDA digit
          OUT

          LDA zero   ; prepare for finding second digit
          BRA enter2

loop2     STA input
          LDA digit  ; increment digit
          ADD one
enter2    STA digit
          LDA input
          SUB ten
          BRP loop2
          LDA digit  ; output number of 10s
          OUT
          LDA input  ; output remainder
          OUT
zero      HLT

one       DAT 001
ten       DAT 010
hundred   DAT 100

input     DAT
digit     DAT

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