IMPLEMENTATION OF SYMBOL TABLE
AIM: To write a program for implementing Symbol Table using C.
ALGORITHM:
Step 1: Start the program for performing insert, display, delete, search and modify
option in symbol table
Step 2: Define the structure of the Symbol Table
Step 3: Enter the choice for performing the operations in the symbol Table
Step 4: If the entered choice is 1, search the symbol table for the symbol to be inserted. If
the symbol is already present, it displays “Duplicate Symbol”. Else, insert the
symbol and the corresponding address in the symbol table.
Step 5: If the entered choice is 2, the symbols present in the symbol table are displayed.
Step 6: If the entered choice is 3, the symbol to be deleted is searched in the symbol table.
Step 7: If it is not found in the symbol table it displays “Label Not found”. Else, the symbol is
deleted.
Step 8: If the entered choice is 5, the symbol to be modified is searched in the symbol table.
The label or address or both can be modified.
PROGRAM:
# 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--;
}
}
OUTPUT:
SYMBOL TABLE IMPLEMENTATION
1.INSERT
2.DISPLAY
3.DELETE
4.SEARCH
5.MODIFY
6.END
Enter your option:1
Enter the label: A
Enter the address: 10
LABEL ADDRESS
A 10
SYMBOL TABLE IMPLEMENTATION
1.INSERT
2.DISPLAY
3.DELETE
4.SEARCH
5.MODIFY
6.END
Enter your option:1
Enter the label: B
Enter the address: 11
LABEL ADDRESS
A 10
B 11
SYMBOL TABLE IMPLEMENTATION
1.INSERT
2.DISPLAY
3.DELETE
4.SEARCH
5.MODIFY
6.END
Enter your option:2
LABEL ADDRESS
A 10
B 11
SYMBOL TABLE IMPLEMENTATION
1.INSERT
2.DISPLAY
3.DELETE
4.SEARCH
5.MODIFY
6.END
Enter your option:3
Enter the label to be deleted: A
LABEL ADDRESS
B 11
SYMBOL TABLE IMPLEMENTATION
1.INSERT
2.DISPLAY
3.DELETE
4.SEARCH
5.MODIFY
6.END
Enter your option:4
Enter the label to be searched: A
The label is not found in the symbol table.
SYMBOL TABLE IMPLEMENTATION
1.INSERT
2.DISPLAY
3.DELETE
4.SEARCH
5.MODIFY
6.END
Enter your option:4
Enter the label to be searched: B
The label is already in the symbol table.
SYMBOL TABLE IMPLEMENTATION
1.INSERT
2.DISPLAY
3.DELETE
4.SEARCH
5.MODIFY
6.END
Enter your option:5
what do you want to modify?
1.only the label
2.only the address of a particular label
3.both the label and address
Enter your choice:1
Enter the old label B
Enter the new label A
LABEL ADDRESS
A 11
SYMBOL TABLE IMPLEMENTATION
1.INSERT
2.DISPLAY
3.DELETE
4.SEARCH
5.MODIFY
6.END
Enter your option:6
RESULT:
Thus the program for implementation of Symbol Table is executed and verified.
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