SIC assembler pass 1 C program?

Answer 1

#include<stdio.h>

#include<string.h>

#include<stdlib.h>

void chk_label();

void chk_opcode();

void READ_LINE();

struct optab

{

char code[10],objcode[10];

}myoptab[3]={

{"LDA","00"},

{"JMP","01"},

{"STA","02"}

};

struct symtab{

char symbol[10];

int addr;

}mysymtab[10];

int startaddr,locctr,symcount=0,length;

char line[20],label[8],opcode[8],operand[8],programname[10];

void PASS1()

{

FILE *input,*inter;

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

inter=fopen("inter.txt","w");

printf("LOCATION LABEL\tOPERAND\tOPCODE\n");

printf("_____________________________________");

fgets(line,20,input);

READ_LINE();

if(!strcmp(opcode,"START"))

{

startaddr=atoi(operand);

locctr=startaddr;

strcpy(programname,label);

fprintf(inter,"%s",line);

fgets(line,20,input);

}

else

{

programname[0]='\0';

startaddr=0;

locctr=0;

}

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

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

{

READ_LINE();

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

if(label[0]!='\0')

chk_label();

chk_opcode();

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

fgets(line,20,input);

}

printf("\n %d\t\t%s",locctr,line);

fprintf(inter,"%s",line);

fclose(inter);

fclose(input);

}

void READ_LINE()

{

char buff[8],word1[8],word2[8],word3[8];

int i,j=0,count=0;

label[0]=opcode[0]=operand[0]=word1[0]=word2[0]=word3[0]='\0';

for(i=0;line[i]!='\0';i++)

{

if(line[i]!=' ')

buff[j++]=line[i];

else

{

buff[j]='\0';

strcpy(word3,word2);

strcpy(word2,word1);

strcpy(word1,buff);

j=0;

count++;

}

}

buff[j-1]='\0';

strcpy(word3,word2);

strcpy(word2,word1);

strcpy(word1,buff);

switch(count)

{

case 0:strcpy(opcode,word1);

break;

case 1:strcpy(opcode,word2);

strcpy(operand,word1);

break;

case 2:strcpy(label,word3);

strcpy(opcode,word2);

strcpy(operand,word1);

break;

}

}

void chk_label()

{

int k,dupsym=0;

for(k=0;k<symcount;k++)

if(!strcmp(label,mysymtab[k].symbol))

{

mysymtab[k].addr=-1;

dupsym=1;

break;

}

if(!dupsym)

{

strcpy(mysymtab[symcount].symbol,label);

mysymtab[symcount++].addr=locctr;

}

}

void chk_opcode()

{

int k=0,found=0;

for(k=0;k<3;k++)

if(!strcmp(opcode,myoptab[k].code))

{

locctr+=3;

found=1;

break;

}

if(!found)

{

if(!strcmp( opcode,"WORD"))

locctr+=3;

else if (!strcmp(opcode,"RESW"))

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

else if(!strcmp(opcode,"RESB"))

locctr+=atoi(operand);

}

}

int main()

{

PASS1();

length=locctr-startaddr;

}