This is how stack and queue works in C programming language

queue.c

#include <stdio.h>


struct QueueNode{
    char value;
    struct QueueNode* next;
};

int main()
{
    char str[] = "Queue is working like FIFO";
    
    //pointer to the head
    struct QueueNode* first;
    
    //allocating memory for head of the queue
    first = malloc(sizeof(struct QueueNode));
    
    //pushing char sequence in queue
    
    struct QueueNode * prev;
    struct QueueNode * curr=first;
    
    printf("Starting to push all of the elements to queue: \n");
    
    int i;
    for(i=0;i<sizeof(str);i++){
        curr->value = str[i];
        printf("Pushing to queue %c \n",curr->value);
        
        //saving pointer to current curr before rewriting curr with new value
        prev = curr;
        
        //rewriting curr with adress to new free portion of memory
        curr = malloc(sizeof(struct QueueNode));
    
        prev->next = curr;
        //NULL next pointer means the end of the Queue
        curr->next = NULL;
    }
    
    //setting current pointer to he HEAD
    curr=first;
    printf("\n\nPoping all element from queue:\n");
    
    while(curr->next!=NULL){
        printf("Poping from queue %c \n",curr->value);
        
        //deleting node
        struct QueueNode* temp = curr;
        curr = curr->next;
        free(temp);
    }
    
   return 0;
}

stack.c

#include <stdio.h>


struct StackNode{
    char value;
    struct StackNode* prev;
};

int main()
{
    char str[] = "Stack is working like FILO";
    
    //pointer we will working with
    struct StackNode* node;
    
    //Creating first node in StackNode
    //it will be newer used
    node = malloc(sizeof(struct StackNode));
    node->prev = NULL;
    
    //pushing char sequence in stack
    int i;
    printf("Starting to push all of the elements to stack: \n");
    for(i=0;i<sizeof(str);i++){
        struct StackNode * temp = node;
        node = malloc(sizeof(struct StackNode));
        node->value = str[i];
        node->prev = temp;
        printf("Pushing to stack %c \n",node->value);
    }
    printf("\n\nPoping all element from stack:\n");
    while(node->prev!=NULL){
        printf("Poping from stack %c \n",node->value);
        
        //deleting node
        struct StackNode* temp = node;
        node = node->prev;
        free(temp);
    }
    
   return 0;
}