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Added python version of pass 1 and pass 2 assembler (a1).

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K 2024-11-06 15:15:39 +05:30
parent f489de94f7
commit c818e00447
Signed by: notkshitij
GPG Key ID: C5B8BC7530F8F43F
2 changed files with 117 additions and 0 deletions

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# Assignment A1 - Pass 1 and pass 2 assembler
# Example Opcode Table (OPTAB)
OPTAB = {
"LOAD": "01",
"STORE": "02",
"ADD": "03",
"SUB": "04",
"JMP": "05"
}
# Example Assembler Directives
DIRECTIVES = ["START", "END", "WORD", "RESW", "RESB"]
# Symbol Table (SYMTAB) and Intermediate Code
SYMTAB = {}
intermediate_code = []
# Pass-I: Generates the symbol table and intermediate code
def pass1(input_lines):
locctr = 0
start_address = 0
for line in input_lines:
label, opcode, operand = parse_line(line.strip())
if opcode == "START":
start_address = int(operand)
locctr = start_address
intermediate_code.append((locctr, label, opcode, operand))
continue
# Process label
if label:
if label in SYMTAB:
print(f"Error: Duplicate symbol {label}")
SYMTAB[label] = locctr
# Process opcode
if opcode in OPTAB:
intermediate_code.append((locctr, label, opcode, operand))
locctr += 3 # Assume all instructions are 3 bytes
elif opcode in DIRECTIVES:
if opcode == "WORD":
locctr += 3
elif opcode == "RESW":
locctr += 3 * int(operand)
elif opcode == "RESB":
locctr += int(operand)
elif opcode == "END":
intermediate_code.append((locctr, label, opcode, operand))
break
else:
print(f"Error: Invalid opcode {opcode}")
return start_address, intermediate_code
# Parse a line of input (splits line into label, opcode, operand)
def parse_line(line):
parts = line.split()
label = parts[0] if len(parts) == 3 else None
opcode = parts[1] if len(parts) == 3 else parts[0]
operand = parts[2] if len(parts) == 3 else parts[1] if len(parts) == 2 else None
return label, opcode, operand
# Pass-II: Generates the final machine code
def pass2(start_address, intermediate_code):
final_code = []
for locctr, label, opcode, operand in intermediate_code:
if opcode in OPTAB:
machine_code = OPTAB[opcode]
if operand in SYMTAB:
address = format(SYMTAB[operand], '04X') # 4-digit hex address
else:
address = '0000' # Default if symbol not found
final_code.append(f"{locctr:04X} {machine_code} {address}")
elif opcode == "WORD":
final_code.append(f"{locctr:04X} {int(operand):06X}")
elif opcode == "RESW" or opcode == "RESB":
final_code.append(f"{locctr:04X} ----")
elif opcode == "END":
final_code.append(f"{locctr:04X} END")
return final_code
# Main function to read the input file and run both passes
def main():
# Read the assembly code from input.txt
with open("assemblerIP.txt", "r") as file:
input_lines = file.readlines()
# Run Pass-I
start_address, intermediate_code = pass1(input_lines)
# Display Symbol Table and Intermediate Code
print("\nPass-I Output:")
print("Symbol Table (SYMTAB):", SYMTAB)
print("\nIntermediate Code:")
for entry in intermediate_code:
print(entry)
# Run Pass-II
final_code = pass2(start_address, intermediate_code)
# Display Final Machine Code
print("\nPass-II Output (Final Machine Code):")
for code in final_code:
print(code)
# Run the main function
if __name__ == "__main__":
main()

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COPY START 1000
FIRST LOAD ALPHA
ADD BETA
STORE GAMMA
ALPHA WORD 5
BETA RESW 1
GAMMA RESB 1
END FIRST