PASS ONE OF A TWO PASS ASSEMBLER

PASS ONE OF A TWO PASS ASSEMBLER

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

            char opcode[10],mnemonic[3],operand[10],label[10],code[10];

            int locctr,start,length;

            FILE *fp1,*fp2,*fp3,*fp4;

            clrscr();

            printf("\nPass One Of A Two Pass Assembler:");

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

            fp1=fopen("input.txt","r");

            fp2=fopen("symtb1.txt","w");

            fp3=fopen("out.txt","w");

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

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

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

            {

              start=atoi(operand);

              locctr=start;

              fprintf(fp3,"\t%s\t%s\t%s\n",label,opcode,operand);

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

            }

            else

              locctr=0;

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

            {

              fprintf(fp3,"%d\t",locctr);

              if(strcmp(label,"**")!=0)

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

              fscanf(fp4,"%s%s",code,mnemonic);

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

              {

                if(strcmp(opcode,code)==0)

                {

                  locctr+=3;  break;

                }

                fscanf(fp4,"%s%s",code,mnemonic);

              }

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

                locctr+=3;

              else if(strcmp(opcode,"RESW")==0)

                locctr+=(3*(atoi(operand)));

              else if(strcmp(opcode,"RESB")==0)

                locctr+=(atoi(operand));

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

                ++locctr;

              fprintf(fp3,"%s\t%s\t%s\n",label,opcode,operand);

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

            }

            fprintf(fp3,"%d\t%s\t%s\t%s\n",locctr,label,opcode,operand);

            length=locctr-start;

            printf("\nThe Length Of The Program Is...%d",length);

            fclose(fp1);

            fclose(fp2);

            fclose(fp3);

            fclose(fp4);

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

            getch();

}

OUTPUT:

Pass One Of A Two Pass Assembler:

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

The Length Of The Program Is...18

Program Completed Successfully...

INPUT FILES:

INPUT.TXT

**            START           1000

**            LDA               VAR1

**            MUL              VAR2

**            STA                ANS

VAR1     WORD           11

VAR2     WORD           12

ANS        RESW            1

**            END               **

OPTAB.TXT

START            *

ADD              18

DIV                24

LDA               00

LDCH            50

MUL              20

STA                0C

STCH             54

SUB               1C

END               *

OUTPUT FILES:

SYMTB1.TXT

VAR1      1009

VAR2      1012

ANS         1015

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             **