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C Program Code for Stack Data Structure
Storage of data in the memory unit of a computer system affects the speed of program execution by the CPU. If virtual memory and cache memory can manage large volume of data and provide faster access to them, stacks are memory areas that store function attributes in a Last In First Out manner (LIFO). Whenever a function is called, its parameters and local variables get pushed to the top of the stack for faster execution. After the function exits returning values, it gets removed and the next function is being pushed to the top. The main operations push and pop in a stack are best illustrated through the abstract data structure using pointers.
C program for implementing stack operations takes function code as the data item in the structure. Functions are identified using this code and the stack is built in the order of Last in First out manner. Different steps involved are creation, pushing and removal.
1. Stack creation
Data structure stack contains function code, funcode as the main data item and a pointer to the next function in the stack. Global pointer top always refers to the top of the stack that gets linked to the next element. Recursive function create_stack() is responsible for creating the stack that reads the function codes of each for execution. The temporary variable ptr holds its value and it gets linked to the top pointer.As top always points to the last entered function in a stack, it is made to point to ptr. Recursion of the function builds the stack and whenever the code becomes -999, this process stops.
Flowchart for the function create_stack()
Output
2. Push operation
Push operation accommodates the newly entered function making it the top. This operation is carried out by the function push(sta *ptr) which takes the new function node ptr as the parameter. The function starts by reading the funcode of ptr and assigns values
ptr->next=top;
top=ptr;
The top pointer is made to point to ptr.
Flowchart for the function push(sta *)
Output of push operation
3. Pop operation
Functions are removed from stack after they are executed. This is done by the pop operation that removes the last entered ones first. Function pop() does this task that refers pointer ptr to top first and makes top to point to the function next to it. Then ptr is freed from the memory using the free() operator.
Flowchart for the function pop()
Output of pop operation
4. Displaying a stack
Displaying the stack is another important part of the program. Just like we display nodes in the linked list, stack elements also can be displayed. Pointer cur is made to point to top and the value cur->funcode is displayed each time the loop is executed. Pointer cur is incremented to point to the next element of the stack and the loop exits when the value of cur becomes NULL.
Flowchart for the function display()
A stack can be said to be a restricted data structure, on account of the lesser operations performed on it. Stack elements follow a natural order as they are removed from the stack in the reverse order to the order of their addition. Therefore, the lower elements are those that have been on the stack for the longest.
#include<stdio.h>
#include<conio.h>
#include<alloc.h>
struct stack
{
int funccode;
struct stack *next;
};
typedef struct stack sta;
sta *top;
void main()
{
int ch=1;
sta *ptr;
void create_stack();
void push(sta *);
void pop(void);
void display(void);
clrscr();
printf("\n\n\tCreate stack(-999 to end):\n\n");
create_stack();
printf("\n\n\n\t\t\tCreated stack is:");
printf("\n\t\t\t----------------\n\n\t");
display();
clrscr();
display();
while(ch!=3)
{
printf("\n\n\t\tStack operations:");
printf("\n\t\t------------------");
printf("\n\n\t\t1. Push");
printf("\n\n\t\t2. Pop");
printf("\n\n\t\t3. Exit");
printf("\n\n\tEnter your choice:");
scanf("%d", &ch);
switch(ch)
{
case 1: ptr=(sta *)malloc(sizeof(sta *));
push(ptr);
printf("\n\n\n\t\t\tStack after push operation is:");
display();
clrscr();
break;
case 2: pop();
printf("\n\n\n\t\t\tStack after pop operation is:");
display();
break;
case 3: exit(1);
break;
}
clrscr();
display();
}
getch();
}
void create_stack()
{
sta *ptr;
ptr=(sta *)malloc(sizeof(sta *));
printf("\n\tEnter each function code:");
scanf("%d", &ptr->funccode);
if(ptr->funccode!=-999)
{
ptr->next=top;
top=ptr;
create_stack();
}
else
ptr->next=NULL;
}
void push(sta *ptr)
{
printf("\n\tEnter the function code:");
scanf("%d", &ptr->funccode);
ptr->next=top;
top=ptr;
}
void pop()
{
sta *ptr;
ptr=top;
top=top->next;
free(ptr);
}
void display()
{
sta *cur;
printf("\n\n\t");
cur=top;
while(cur)
{
printf("%d----------->", cur->funccode);
cur=cur->next;
}
getch();
}
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© 2013 Radhika Sreekanth
