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uses a octal label such as F , the assembler identifies the specific occurrence of label
1 by comparing all local labels 1 to the current value of the LC. The first such instruction in our example is the ‘JMP Fat LC=17.Clearly,the assembler should look fora octal label with the name ‘1 and a value The smallest such label
has value In the second case, LC and the assembler is looking fora B It needs the label with name ‘1 ’ and a value which is the largest among all values <24.It therefore identifies the label as the ‘1 ’at 13.
EXERCISE If we modify the instruction at 24 above to read 1:LOD RF would the F refer to address 31 or 24?
Ina one-pass assembler, again the labels are recognized and put into the symbol table in the single pass. An instruction using a octal label iB is no problem, since is needs the most recent occurrence of the local label ‘1 in the table. An instruction using an iF is handled like any other future symbol case. An entry is opened in the symbol table with the name iF a type of U and a value which is a pointer to the instruction. In the example above, a snapshot
of the symbol table at LC is Share with your friends: