IMPLEMENTATION OF PASS TWO OF A TWO PASS ASSEMBLER

IMPLEMENTATION OF PASS TWO OF A TWO PASS ASSEMBLER

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

            FILE *fp1,*fp2,*fp3,*fp4;

            char label[10],opcode[10],operand[10],symbol[10],code[10];

            char mnemonic[5],ch,add[10],objcode[10];

            int flag,flag1,locctr,location,loc;

            clrscr();

            printf("\nImplementation Of pass Two Of A Two Pass Assembler:");

            printf("\n---------------------------------------------------\n\n");

            fp1=fopen("out.txt","r");

            fp2=fopen("twoout.txt","w");

            fp3=fopen("optab.txt","r");

            fp4=fopen("symtb1.txt","r");

            fscanf(fp1,"%s%s%s",label,opcode,operand);

            if(strcmp(opcode,"START")==0)

            {

              fprintf(fp2,"%s\t%s\t%s\n",label,opcode,operand);

              fscanf(fp1,"%d%s%s%s",&locctr,label,opcode,operand);

            }

            while(strcmp(opcode,"END")!=0)

            {

              flag=0;

              fscanf(fp3,"%s%s",code,mnemonic);

              while(strcmp(code,"END")!=0)

              {

                if((strcmp(opcode,code)==0) && (strcmp(mnemonic,"*"))!=0)

                {

                  flag=1; break;

                }

                fscanf(fp3,"%s%s",code,mnemonic);

              }

              if(flag==1)

              {

                flag1=0;

                rewind(fp4);

                while(!feof(fp4))

                {

                  fscanf(fp4,"%s%d",symbol,&loc);

                  if(strcmp(symbol,operand)==0)

                  {

                        flag1=1; break;

                  }

                }

                if(flag1==1)

                {

                  itoa(loc,add,10);

                  strcpy(objcode,strcat(mnemonic,add));

                }

              }

              else if(strcmp(opcode,"BYTE")==0 || strcmp(opcode,"WORD")==0)

              {

                if((operand[0]=='C') || (operand[0]=='X'))

                {

                  ch=operand[2];

                  itoa(ch,add,16);

                  strcpy(objcode,add);

                }

                else

                {

                  itoa(atoi(operand),add,10);

                  strcpy(objcode,add);

                }

              }

              else

              strcpy(objcode,"\0");

              fprintf(fp2,"%s\t%s\t%s\t%d\t%s\n",label,opcode,operand,locctr,objcode);

              fscanf(fp1,"%d%s%s%s",&locctr,label,opcode,operand);

            }

            fprintf(fp2,"%s\t%s\t%s\t%d\n",label,opcode,operand,locctr);

            fclose(fp1);

            fclose(fp2);

            fclose(fp3);

            fclose(fp4);

            printf("Program Completed Successfully...\n");

            getch();

}

OUTPUT:

Implementation Of pass Two Of A Two Pass Assembler:

---------------------------------------------------------------------

Program Completed Successfully...

INPUT FILES:

OUT.TXT

                **           START         1000

1000        **           LDA             VAR1

1003        **           MUL            VAR2

1006       **           STA              ANS

1009        VAR1    WORD         11

1012        VAR2    WORD         12

1015        ANS       RESW          1

1018        **           END             **

OPTAB.TXT

START            *

ADD              18

DIV                24

LDA               00

LDCH            50

MUL              20

STA                0C

STCH             54

SUB               1C

END               *

SYMTB1.TXT

VAR1      1009

VAR2      1012

ANS         1015

OUTPUT FILES:

TWOOUT.TXT

**                START          1000

**                LDA              VAR1       1000       001009

**                MUL             VAR2       1003       201012

**                STA               ANS          1006       0C1015

VAR1         WORD          11               1009       11

VAR2         WORD          12               1012       12

ANS            RESW           1                 1015  

**                END              **               1018