Write a C program to implement relocatable loader?

Answer 1

#include<stdio.h>

#include<conio.h>

#include<string.h>

#include<stdlib.h>

struct object_code

{

int locctr;

char add[10];

}obcode[300];

void main()

{

char input[100][16],output[100][16],binary[20],address[20],stloc[10];

int len,bitmask,loc,tlen=0,tloc,textloc,i=0,location,j,k,count=0,start,n,num=0,inc=0;

FILE *fp1,*fp2;

clrscr();

fp1=fopen("linput.dat","r");

fp2=fopen("reloadout.dat","w");

printf("Enter the location where the program has to be loaded:");

scanf("%s",stloc);

start=atoi(stloc);

location=start;

tloc=start;

fscanf(fp1,"%s",input[i]);

while(strcmp(input[i],"T")!=0)

{

strcpy(output[i],input[i]);

i++;

fscanf(fp1,"%s",input[i]);

strcpy(output[i],input[i]);

}

itoa(start,output[2],10);

while(strcmp(input[i],"E")!=0)

{

strcpy(output[i],input[i]);

if(strcmp(input[i],"T")==0)

{

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

{

i++;

fscanf(fp1,"%s",input[i]);

strcpy(output[i],input[i]);

}

bitmask=atoi(output[i]);

itoa(bitmask,binary,2);

strcpy(output[i],NULL);

textloc=atoi(output[i-2]);

textloc=textloc+start;

itoa(textloc,output[i-2],10);

for(n=0;n<(textloc-(tloc+tlen));n++)

{

strcpy(obcode[inc].add,"xx");

obcode[inc++].locctr=location++;

}

tlen=atoi(output[i-1]);

tloc=textloc;

k=0;

}

else

{

if(binary[k]==1)

{

num=0;

len=strlen(output[i]);

strcpy(address,NULL);

for(j=2;j<len;j++)

{

address[num]=output[i][j];

output[i][j]='\0';

num++;

}

loc=atoi(address);

loc=loc+start;

itoa(loc,address,10);

strcat(output[i],address);

}

k++;

len=strlen(output[i]);

num=0;

for(n=0;n<len;n++)

{

obcode[inc].add[num++]=output[i][n];

if(num>1)

{

obcode[inc++].locctr=location++;

num=0;

}

}

}

i++;

fscanf(fp1,"%s",input[i]);

}

strcpy(output[i],input[i]);

i++;

fscanf(fp1,"%s",input[i]);

loc=atoi(input[i]);

loc=loc+start;

strcpy(output[i],itoa(loc,address,10));

count=0;

i=0;

n=0;

fprintf(fp2,"%d\t",obcode[n].locctr);

for(n=0;n<inc;n++)

{

fprintf(fp2,"%s",obcode[n].add);

i++;

if(i>3)

{

fprintf(fp2,"\t");

i=0;

count++;

}

if(count>3)

{

fprintf(fp2,"\n%d\t",obcode[n+1].locctr);

count=0;

}

}

getch();

}