#include<stdio.h>
#include<stdlib.h>
 int MAX=4,count;
 struct student
 {
     char usn[10];
     char name[89];
     char branch[4];
     int sem;
     char phno[10];
     struct student*next;
 };
 typedef struct student NODE;
 NODE*head;
  int countnodes()
  {
      NODE*p;
      count=0;
      p=head;
      while(p!=NULL)
      {
          p=p->next;
          count++;
      }
      return count;
  }
  
  NODE*getnode()
  {
      NODE*newnode;
      newnode=(NODE*)malloc(sizeof(NODE));
       printf("\nenter usn,name,branch,sem,phno\n");
      fflush(stdin);
      gets(newnode->usn);
      fflush(stdin);
         gets(newnode->name);
      fflush(stdin);
         gets(newnode->branch);
      fflush(stdin);
         gets(newnode->sem);
         scanf("%d",&(newnode->sem));
      fflush(stdin);
         gets(newnode->phno);
         newnode->next=NULL;
      return newnode;
  }
  NODE*display()
  {
      NODE*p;
      if(head==NULL)
      printf("\nno student data\n");
      else
      {
          p=head;
          printf("\n____ STUDENT DATA____\n");
          printf("\nusn\ntname\t\tbranch\tsem\tphno");
          while(p!=NULL)
          {
                  printf("\n%s\t%s\t\t%s\t%d\t%s",p->usn,p->name,p->branch,p->sem,p->phno);
                  p=p->next;
          }printf("\nthe no of nodes in list is:%d",countnodes(head));
      }
      return head;
  }
  NODE* create()
  {
      NODE*newnode;
      if(head==NULL)
      {
          newnode=getnode();
          head=newnode;
      }
      else
      {
          newnode=getnode();
          newnode->next=head;
          head=newnode;
          
      }
      return head;
  }
  void insert_front()
  {
      if(countnodes(head)==MAX)
      printf("\nlist is full!");
      else
      head=create();
  }
  void insert_rear()
  {
      NODE*p,*newnode;
      p=head;
      if(countnodes(head)==MAX)
       printf("\nlist is full(QUEUE)!!");
       else
       {
           if(head==NULL)
           {
               newnode=getnode();
               head=newnode;
           }
          
           else
           {
               newnode=getnode(head);
               while(p->next!=NULL)
               {
                   p=p->next;
               }
               p->next=newnode;
           }
       }
      
  }
  void insert()
  {
      int ch;
      do
      {
          printf("\n1.insert at front(first)\t2.insert at END(rear/last)\t3.exit");
          printf("\nenter your choice:");
          scanf("%d",&ch);
          switch(ch)
          {
              case 1:insert_front();break;
              case 2:insert_rear();break;
              case 3:break;
          }
          display();
      }
      while(ch!=3);
     
  }
  void delete_front()
  {
      NODE*p;
      if(head==NULL)
      printf("\nlist is empty/underflow(STACK/QUEUE)");
      else
     {
         p=head;
         head=head->next;
         free(p);
         printf("\nfront(first)node is deleted");
         
     }
  }
  void delete_rear()
  {
      NODE*p,*q;
      p=head;
      if(count==1)
      {
          delete_front();
          return;
      }
      while(p->next!=NULL)
      {
          q=p;
          p=p->next;
      }
      free(p);
      q->next=NULL;
      printf("\nlast(end)entry is deleted");
      
  }
  void del()
  {
      int ch;
      do
      {
          printf("\n1.delete from front(first)\t2.delete from end(rear/last)\t3.exit");
          printf("nenter your choice:");
          scanf("%d",&ch);
          switch(ch)
          {
              case 1: delete_front();
              break;
              case 2:delete_rear();
              break;
              case 3: break;
          }
          display();
      }while(ch!=3);
  }
  NODE*stack()
  {
      int ch;
      do
      {
          printf("\nSSL used as stack...");
          printf("\n1.1.insert at front(PUSH)\t2.delete from front(POP))\t3.exit");
          printf("\nenter your choice:");
          scanf("%d",&ch);
          switch(ch)
          {
              case 1:insert_front();
              break;
              case 2:delete_front();
              break;
              case 3:break;
          }
          display();
      }while(ch!=3);
  }
  void queue()
  {
      int ch;
      do
      {
          printf("\nSSL used as queue...");
          printf("\n 1.insert at rear(insert)\t 2.delete front(delete))\t.exit");
          printf("\nenter your choice:");
          scanf("%d",&ch);
          switch(ch)
          {
             case 1:insert_rear(); break;
             case 2:delete_front();break;
             case 3:break;
          }
          display();
      }while(ch!=3);
  }
  void main()
  {
      int ch,i,n;
      head=NULL;
      printf("\n*----------student database----------*");
      do
      {
          printf("\n 1.create\t 2.display\t 3.insert\t 5.stack\t 6.queue\t 7.exit");
          printf("\nenter your choice:");
          scanf("%d", &ch);
          switch(ch)
          {
              case 1 : printf("\nhow many student data you want to create:");
              scanf("%d",&n);
              for(i=0;i<n;i++)
              create();
              break;
              case 2:display();
              break;
              case 3:insert();
              break;
              case 4:del();
              break;
              case 5:stack();
              break;
              case 6:queue();
              break;
              case 7:exit(0);
          }
      }while(ch!=7);
  }
   

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Read inputs from stdin

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#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
} 

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
} 

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}  

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition); 

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}