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Chapter 2 Assemblers
-- Basic Assembler Functions
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Outline
∎ Basic assembler functions
∎ A simple SIC assembler
∎ Assembler algorithm and data structure
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Basic assembler functions
∎ Translating mnemonic operation codes to
their machine language equivalents
∎ Assigning machine addresses to symbolic
labels
Source Program
• Mnemonic opcode
• Symbol
Assembler
Object code
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Assembler directive
∎ Assembler directives are pseudo instructions
∎
They provide instructions to the assembler itself
∎
They are not translated into machine operation codes
∎ SIC assembler directive
∎
START : specify name & starting address
∎
END
: end of source program, specify the first
execution instruction
∎
BYTE, WORD, RESB, RESW
∎
End of record
: a null char (00)
∎
End of file
: a zero-length record
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Example program (Figure 2.1 pp. 45)
Forward
reference
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Example program (Figure 2.1 pp. 45)
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Example program (Figure 2.1 pp. 45)
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Example program (Figure 2.1 pp. 45)
∎ Purpose of example program
∎
Reads records from input device (code F1)
∎
Copies them to output device (code 05)
∎
At the end of the file, writes EOF on the output device, then RSUB
