#include<stdio.h>
# define MAX 5
int cqueue_arr[MAX];
int front = -1;
int rear = -1;
void insert(int item)
{
   if((front == 0 && rear == MAX-1) || (front == rear+1))
   {
     printf("Queue Overflow n");
     return;
   }
   if(front == -1)
   {
     front = 0;
     rear = 0;
   }
   else
   {
     if(rear == MAX-1)
        rear = 0;
     else
       rear = rear+1;
   }
   cqueue_arr[rear] = item ;
}
void deletion()
{
   if(front == -1)
   {
     printf("Queue Underflown");
     return ;
   }
   printf("Element deleted from queue is : %dn",cqueue_arr[front]);
   if(front == rear)
   {
     front = -1;
     rear=-1;
   }
   else
   {
     if(front == MAX-1)
       front = 0;
     else
       front = front+1;
   }
}
void display()
{
   int front_pos = front,rear_pos = rear;
   if(front == -1)
   {
     printf("Queue is emptyn");
     return;
   }
   printf("Queue elements :n");
   if( front_pos <= rear_pos )
   while(front_pos <= rear_pos)
   {
     printf("%d ",cqueue_arr[front_pos]);
     front_pos++;
   }
   else
   {
     while(front_pos <= MAX-1)
     {
       printf("%d ",cqueue_arr[front_pos])
       front_pos++;
     }
     front_pos = 0;
     while(front_pos <= rear_pos)
     {
       printf("%d ",cqueue_arr[front_pos]);
       front_pos++;
     }
   }
   printf("n");
}
int main()
{
   int choice,item;
do
{
   printf("1.Insertn");
   printf("2.Deleten");
   printf("3.Displayn");
   printf("4.Quitn");
   printf("Enter your choice : ");
  scanf("%d",&choice);
switch(choice)
{
case 1 :
printf("Input the element for insertion in queue : ");
scanf("%d", &item);
insert(item);
break;
case 2 :
deletion();
break;
case 3:
display();
break;
case 4:
break;
default:
printf("Wrong choicen");
}
}while(choice!=4);
return 0;
}
by

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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
}