/******************************************************************************/
/* C Program to implement SYMBOL TABLE */
#include<stdio.h>
#include<conio.h>
#include<alloc.h>
#include<string.h>
#define null 0
int size=0;
void insert();
void del();
int search(char lab[]);
void modify();
void display();
struct symbtab
{
char
label[10];
int
addr;
struct
symbtab *next;
};
struct symbtab *first,*last;
void main()
{
int op;
int y;
char
la[10];
clrscr();
do
{
printf("\nSYMBOL
TABLE IMPLEMENTATION\n");
printf("1.INSERT\n");
printf("2.DISPLAY\n");
printf("3.DELETE\n");
printf("4.SEARCH\n");
printf("5.MODIFY\n");
printf("6.END\n");
printf("\nEnter
your option: ");
scanf("%d",&op);
switch(op)
{
case
1:
insert();
display();
break;
case
2:
display();
break;
case
3:
del();
display();
break;
case
4:
printf("Enter
the label to be searched: ");
scanf("%s",la);
y=search(la);
if(y==1)
printf("The
label is already in the symbol table\n");
else
printf("The
label is not found in the symbol tablel\n");
break;
case
5:
modify();
display();
break;
case
6:
break;
}
}
while(op<6);
getch();
}
void insert()
{
int n;
char
l[10];
printf("Enter
the label: ");
scanf("%s",l);
n=search(l);
if(n==1)
printf("The
label is already in the symbol table. Duplicate cant be inserted\n");
else
{
struct
symbtab *p;
p=malloc(sizeof(struct
symbtab));
strcpy(p->label,l);
printf("Enter
the address: ");
scanf("%d",&p->addr);
p->next=null;
if(size==0)
{
first=p;
last=p;
}
else
{
last->next=p;
last=p;
}
size++;
}
}
void display()
{
int i;
struct
symbtab *p;
p=first;
printf("LABEL\tADDRESS\n");
for(i=0;i<size;i++)
{
printf("%s\t%d\n",p->label,p->addr);
p=p->next;
}
}
int search(char lab[])
{
int
i,flag=0;
struct
symbtab *p;
p=first;
for(i=0;i<size;i++)
{
if(strcmp(p->label,lab)==0)
flag=1;
p=p->next;
}
return
flag;
}
void modify()
{
char
l[10],nl[10];
int
add,choice,i,s;
struct
symbtab *p;
p=first;
printf("What
do you want to modify?\n");
printf("1.Only
the label\n");
printf("2.Only
the address of a particular label\n");
printf("3.Both
the label and address\n");
printf("Enter
your choice: ");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("Enter
the old label\n");
scanf("%s",l);
printf("Enter
the new label: ");
scanf("%s",nl);
s=search(l);
if(s==0)
printf("\nNo
such label");
else
{
for(i=0;i<size;i++)
{
if(strcmp(p->label,l)==0)
{
strcpy(p->label,nl);
}
p=p->next;
}
}
break;
case
2:
printf("Enter
the label whose address is to be modified: ");
scanf("%s",l);
printf("Enter
the new address: ");
scanf("%d",&add);
s=search(l);
if(s==0)
printf("\nNo
such label");
else
{
for(i=0;i<size;i++)
{
if(strcmp(p->label,l)==0)
{
p->addr=add;
}
p=p->next;
}
}
break;
case
3:
printf("Enter
the old label: ");
scanf("%s",l);
printf("Enter
the new label: ");
scanf("%s",nl);
printf("Enter
the new address: ");
scanf("%d",&add);
s=search(l);
if(s==0)
printf("\nNo
such label");
else
{
for(i=0;i<size;i++)
{
if(strcmp(p->label,l)==0)
{
strcpy(p->label,nl);
p->addr=add;
}
p=p->next;
}
}
break;
}
}
void del()
{
int a;
char
l[10];
struct
symbtab *p,*q;
p=first;
printf("Enter
the label to be deleted: ");
scanf("%s",l);
a=search(l);
if(a==0)
printf("Label
not found\n");
else
{
if(strcmp(first->label,l)==0)
first=first->next;
else
if(strcmp(last->label,l)==0)
{
q=p->next;
while(strcmp(q->label,l)!=0)
{
p=p->next;
q=q->next;
}
p->next=null;
last=p;
}
else
{
q=p->next;
while(strcmp(q->label,l)!=0)
{
p=p->next;
q=q->next;
}
p->next=q->next;
}
size--;
}
}
/******************************************************************************/
