April 23, 2014
We studied a simple assembler for a hypothetical computer in the two previous exercises. Today we finish our look at the assembler by writing a program that produces neat listings, like this one for our sample program:
# print sum of input numbers (terminated by zero) 000: 03010 ld zero # initialize sum to zero 001: 04011 st sum 002: 01000 loop get # read a number 003: 08007 jz done # no more input if number is zero 004: 05011 add sum # add input to accumulated sum 005: 04011 st sum # store new value back in sum 006: 09002 j loop # go back and read another number 007: 03011 done ld sum # print sum 008: 02000 put 009: 10000 halt 010: 00000 zero const 0 011: 00000 sum const
The listing shows the memory address in the first column, the contents of memory at the beginning of the program in the second column, the mnemonic label in the third column, the opcode in the fourth column, the object of the operation in the fifth column, and the comment in the sixth column.
Your task is to write a program that produces assembler listings. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.