# 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 symtab *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("Enter 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");
else{
printf("The label is not found in the symbol table");
}
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 already exists. 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\n");
scanf("%s",nl);
s=search(l);
if(s==0){
printf("NO 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 modified\n");
scanf("%s",l);
printf("Enter the new address\n");
scanf("%d",&add);
s=search(l);
if(s==0){
printf("NO 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("NO 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\n");
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--;
}}
