Question

Write and explain the algorithm for pass 1 of a linking loader.

Answer 1

Hey dear,


Source code in c program performing passes one linking loader 
# include <stdio.h>
# include <conio.h>
# include <string.h>
# define MAX 20
struct estab
{
char csname[10];
char extsym[10];
int address;
int length;
}es[MAX];
void main()
{
char input[10],name[10],symbol[10];
int count=0,progaddr,csaddr,add,len;
FILE *fp1,*fp2;
clrscr();
fp1=fopen("linkinput.dat","r");
fp2=fopen("loadmap.dat","w");
printf("Enter the location where the program has to be loaded : ");
scanf("%d",&progaddr);
csaddr=progaddr;
fprintf(fp2,"CS_NAME\tEXT_SYM_NAME\tADDRESS\tLENGTH\n");
fprintf(fp2,"--------------------------------------\n");
fscanf(fp1,"%s",input);
while(strcmp(input,"END")!=0)
{
if(strcmp(input,"H")==0)
{
fscanf(fp1,"%s",name);
strcpy(es[count].csname,name);
strcpy(es[count].extsym,"**");
fscanf(fp1,"%d",&add);
es[count].address=add+csaddr;
fscanf(fp1,"%d",&len);
es[count].length=len;
fprintf(fp2,"%s\t%s\t\t%d\t%d\n",es[count].csname,es[count].extsym,es[count].address,es[count].length);
count++;
}
else if(strcmp(input,"D")==0)
{
fscanf(fp1,"%s",input);
while(strcmp(input,"R")!=0)
{
strcpy(es[count].csname,"**");
strcpy(es[count].extsym,input);
fscanf(fp1,"%d",&add);
// printf("CSADDR = %d",csaddr);
es[count].address=add+csaddr;
es[count].length=0;
fprintf(fp2,"%s\t%s\t\t%d\t%d\n",es[count].csname,es[count].extsym,es[count].address,es[count].length);
count++;
fscanf(fp1,"%s",input);
}
csaddr=csaddr+len;
}
else if(strcmp(input,"T")==0)
{
while(strcmp(input,"E")!=0)
fscanf(fp1,"%s",input);
}
fscanf(fp1,"%s",input);
}
fprintf(fp2,"--------------------------------------\n");
fclose(fp1);
fclose(fp2);
printf("FINISHED\n");
getch();
}
Hope it will help u...