INPUT FILE:
START 100
READ A
A READ BREG, A
ADD BREG, B
LOOP MOVEM AREG, C
STOP
A DS 1
B DS 1
END
PROGRAM:
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
typedef struct node
{
char symb[20];
int decl,used;
struct node *next;
}NODE;
NODE *first, *last;
void add_symb1(char *s)
{
NODE *p;
p=(NODE*)malloc(sizeof(NODE));
strcpy(p->symb,s);
p->decl = 1;
p->used = 0;
p->next = NULL;
if(first==NULL)
first = p;
else
last->next = p;
last = p;
}
void add_symb2(char *s)
{
NODE *p;
p = (NODE*)malloc(sizeof(NODE));
strcpy(p->symb,s);
p->decl = 0;
p->used = 1;
p->next = NULL;
if(first==NULL)
first=p;
else
last->next = p;
last=p;
}
NODE * search(char *s)
{
NODE *p;
p = first;
while(p!=NULL)
{
if(strcmp(p->symb,s)==0)
return p;
p=p->next;
}
return NULL;
}
char optab[][6]={"STOP","ADD","SUB","MULT",
"MOVER","MOVEM","COMP","BC",
"DIV","READ","PRINT"};
int search_op(char *s)
{
int i;
for(i=0;i<11;i++)
if(strcmp(optab[i],s)==0)
return i;
return -1;
}
int main()
{
NODE *p;
FILE *fp;
char buff[80],t1[20],t2[20],
t3[20],t4[20],fname[40];
int n,i;
printf("Enter source file name:");
scanf("%s",fname);
fp = fopen(fname,"r");
if(fp==NULL)
{
printf("File %s not found.\n",fname);
exit(1);
}
while(fgets(buff,80,fp)!=NULL)
{
n = sscanf(buff,"%s %s %s %s",t1,t2,t3,t4);
switch(n)
{
case 2:
if(strcmp(t1,"START")==0)
break;
i = search_op(t1);
if(i==9 || i==10) // READ or PRINT
{
p=search(t2);
if(p==NULL)
add_symb2(t2);
else
p->used=1;
break;
}
p = search(t1);
if(p==NULL)
add_symb1(t1);
else
p->decl++;
break;
case 3:
i = search_op(t1);
if(i>=1 && i<=8) // ADD to DIV
{
p = search(t3);
if(p==NULL)
add_symb2(t3);
else
p->used=1;
break;
}
if(strcmp(t2,"DS")==0 ||
strcmp(t2,"DC")==0)
{
p=search(t1);
if(p==NULL)
add_symb1(t1);
else
p->decl++;
break;
}
p=search(t1);
if(p==NULL)
add_symb1(t1);
else
p->decl++;
p=search(t3);
if(p==NULL)
add_symb2(t3);
else
p->used = 1;
break;
case 4:
p = search(t1);
if(p==NULL)
add_symb1(t1);
else
p->decl++;
p = search(t4);
if(p==NULL)
add_symb2(t4);
else
p->used =1;
} // switch
} // while
fclose(fp);
p = first;
while(p!=NULL)
{
if(p->decl!=0 && p->used==0)
printf("Symb %s declared but not used.\n",p->symb);
if(p->used==1 && p->decl==0)
printf("Symb %s used but not declared.\n",p->symb);
if(p->decl>1)
printf("Symb %s redeclared.\n",p->symb);
p=p->next;
}
return 0;
}
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