IMPLEMENTATION OF PASS 2 OF A TWO-PASS ASSEMBLER Using Opcode

Aim
To implement of pass two of pass two assembler in CS1207 SYSTEM SOFTWARE LAB using opcode
Algorithm
Start the program
Initialize all the variables
Open a file by name
fp1=fopen("assmlist.dat","w");
fp2=fopen("symtab.dat","r");

fp3=fopen("intermediate.dat","r");
fp4=fopen("optab.dat","r");
Read the content of the file
If opcode is BYTE
if(strcmp(opcode,"BYTE")==0)
Then
fprintf(fp1,"%d\t%s\t%s\t%s\t",address,label,opcode,operand);
Else if opcode is WORD
else if(strcmp(opcode,"WORD")==0)
then
fprintf(fp1,"%d\t%s\t%s\t%s\t00000%s\n",address,label,opcode,operand,a);
Else perform
else if((strcmp(opcode,"RESB")==0)(strcmp(opcode,"RESW")==0))
fprintf(fp1,"%d\t%s\t%s\t%s\n",address,label,opcode,operand);
if it is not math anything
else
fprintf(fp1,"%d\t%s\t%s\t%s\t%d0000\n",address,label,opcode,operand,code);
Finally terminate the of pass two of pass two assembler


Source code program in c pass two of pass two assembler
#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<stdlib.h>
void main()
{
char a[10],ad[10],label[10],opcode[10],operand[10],mnemonic[10],symbol[10];
int i,address,code,add,len,actual_len;
FILE *fp1,*fp2,*fp3,*fp4;
clrscr();
fp1=fopen("assmlist.dat","w");
fp2=fopen("symtab.dat","r");
fp3=fopen("intermediate.dat","r");
fp4=fopen("optab.dat","r");
fscanf(fp3,"%s%s%s",label,opcode,operand);
if(strcmp(opcode,"START")==0)
{
fprintf(fp1,"\t%s\t%s\t%s\n",label,opcode,operand);
fscanf(fp3,"%d%s%s%s",&address,label,opcode,operand);
}
while(strcmp(opcode,"END")!=0)
{
if(strcmp(opcode,"BYTE")==0)
{
fprintf(fp1,"%d\t%s\t%s\t%s\t",address,label,opcode,operand);
len=strlen(operand);
actual_len=len-3;
for(i=2;i<(actual_len+2);i++)
{
itoa(operand[i],ad,16);
fprintf(fp1,"%s",ad);
}
fprintf(fp1,"\n");
}
else if(strcmp(opcode,"WORD")==0)
{
len=strlen(operand);
itoa(atoi(operand),a,10);
fprintf(fp1,"%d\t%s\t%s\t%s\t00000%s\n",address,label,opcode,operand,a);
}
else if((strcmp(opcode,"RESB")==0)(strcmp(opcode,"RESW")==0))
{
fprintf(fp1,"%d\t%s\t%s\t%s\n",address,label,opcode,operand);
}
else
{
rewind(fp4);
fscanf(fp4,"%s%d",mnemonic,&code);
while(strcmp(opcode,mnemonic)!=0)
fscanf(fp4,"%s%d",mnemonic,&code);
if(strcmp(operand,"**")==0)
{
fprintf(fp1,"%d\t%s\t%s\t%s\t%d0000\n",address,label,opcode,operand,code);

}
else
{
rewind(fp2);
fscanf(fp2,"%s%d",symbol,&add);
while(strcmp(operand,symbol)!=0)
{
fscanf(fp2,"%s%d",symbol,&add);
}
fprintf(fp1,"%d\t%s\t%s\t%s\t%d%d\n",address,label,opcode,operand,code,add);
}
}
fscanf(fp3,"%d%s%s%s",&address,label,opcode,operand);
}
fprintf(fp1,"%d\t%s\t%s\t%s\n",address,label,opcode,operand);
printf("Finished");
fclose(fp1);
fclose(fp2);
fclose(fp3);
fclose(fp4);
getch();
}


INPUT FILES
INTERMEDIATE.DAT

** START 2000
2000 ** LDA FIVE
2003 ** STA ALPHA
2006 ** LDCH CHARZ
2009 ** STCH C1
2012 ALPHA RESW 1
2015 FIVE WORD 5
2018 CHARZ BYTE C'EOF'
2019 C1 RESB 1
2020 ** END **

OPTAB.DAT
LDA 33
STA 44
LDCH 53
STCH 57
END *

SYMTAB.DAT
ALPHA 2012
FIVE 2015
CHARZ 2018
C1 2019

OUTPUT FILE :
ASSMLIST.DAT
** START 2000
2000 ** LDA FIVE 332015
2003 ** STA ALPHA 442012
2006 ** LDCH CHARZ 532018
2009 ** STCH C1 572019
2012 ALPHA RESW 1
2015 FIVE WORD 5 000005
2018 CHARZ BYTE C'EOF' 454f46
2019 C1 RESB 1
2020 ** END **

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