110 lines
3.3 KiB
Python
Executable File
110 lines
3.3 KiB
Python
Executable File
# Assignment-A1
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try:
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source = open('source.txt','r')
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data = source.read()
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print('File read successfully\n\n')
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source.seek(0)
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except FileNotFoundError: #A little bit of exception handling
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print('\n\n\nFile Not found. Create a source.txt first.\n\n\n ')
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except IOError:
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print('There was an IO error')
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LT_index = 0 #index of LT table
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ST_index = 0 #index of ST table
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add = 0 # address in source code
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MOT = {'STOP': '00','ADD': '01','SUB': '02','MULT': '03','MOVER': '04','MOVEM': '05','COMP': '06','BC': '07','DIV': '08','READ': '09','PRINT': '10','START': '01','END': '02','ORIGIN': '03','LTORG': '05','DS': '01','DC': '02','AREG,': '01','BREG,': '02','EQ':'01'}
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ST = []
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code=[]
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LT=[]
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MC = []
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# LT, ST are lists of lists. code= intermediate code table
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def classy(text):
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'''This function will return the class of the word to be inputted in the Intermediate table'''
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text = text.upper()
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if text in ['STOP','ADD','SUB', 'MULT','MOVER','MOVEM','COMP','BC','DIV','READ', 'PRINT']:
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return 'IS'
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elif text in ['START','END','ORIGIN','LTORG']:
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return 'AD'
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elif text in ['DS','DC']:
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return 'DL'
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elif text in ['AREG,','BREG,']: return 'RG'
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elif text in ['EQ']: return 'CC'
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else: return 'None'
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def handle_start():
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'''This function gives you the starting address of the code'''
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line= source.readline()
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words=line.split()
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if words[0].upper()=='START':
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return int(words[1])
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else:
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print("No Start Statement! Abort!\n")
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return 0
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def pass1():
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add=handle_start()
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if not add:
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print("Ending Pass 1 due to Above error.")
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return
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global ST_index, LT_index # to modify global variables, use global keyword
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while True:
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line=source.readline()# handlestart function reads line 1 and we start from the second line.
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if not line:
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break
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words= line.split()
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for w in words:
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w=w.upper()
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if w[0]=='=':
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entry=[LT_index,w, add]
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LT.append(entry)
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LT_index +=1
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elif classy(w)== 'None':
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for term in ST:
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if w== term[1]: break # I check if the label is already present in ST.
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else:
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entry=[ST_index,w, add]
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ST.append(entry)
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ST_index +=1
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add+=1
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print('LT:')
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for a in LT:
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print(a)
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print('\n\n\nST:')
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for a in ST:
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print(a)
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def intermediate():
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source.seek(0)
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while True:
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entry=[]
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ind = 0
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line=source.readline()
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if not line:
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break
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words=line.split()
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for w in words:
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w=w.upper()
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if classy(w)!='None': #it is a directive
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entry.append((classy(w),MOT[w]))
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elif w[0]== '=': #it is a literal.
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for a in LT:
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if a[1]==w:
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ind = a[0]
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break
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entry.append(('L',ind))
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else: #it is a symbol
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for a in ST:
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if a[1]==w:
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ind = a[0]
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break
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entry.append(('S',ind))
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code.append(entry)
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print("\nThe Intermediate code is:")
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for entry in code:
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print(entry)
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pass1()
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intermediate()
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