C Tutorial

C Tutorial C Language Environment Setup Execution flow of C program C printf and Scanf C Data type C Token Variable in C Operators in C Comments in C Escape Sequence in C C – Storage Classes C Decision control statement Loop Statement in C Break, continue and goto statement in C Type Casting in C Function in C Recursion in C String in C C Array Pointer in C Dynamic memory allocation C –Structure Nested Structure in C Union in C File Handling in C C pre-processor Static Function In C Sizeof In C Selection Sort In C Scope Of Variables In C Runtime Vs Compile Time In C Random Access Lseek In C Queue Implementation In C Pseudo Code In C Prototype In C Pointer To Pointer In C Pointer Arithmetic In C Passing Array To Function In C Null Character In C Merge Sort In C Macros In C Library Functions In C Memory Leak In C Int In C Goto And Labels In C Fibonacci Series In C Fflush In C Derived Data Types In C Data Types In C Const Vs Volatile In C Character Set In C Character Class Tests In C Calloc In C C Pointers Arrays In C Include In C Clrscr In C C Vs Java String Literals In C Types Of Pointers In C Variables In C Volatile In C Why C Is A Middle Level Language Infix To Postfix Program In C Ceil function in C LCM of two numbers in C Quick sort in C Static in C function pointer as argument in C Top Array Keywords in C Add two numbers using the function in C Armstrong program in C using function Array, Declaring Arrays and Array Initialization Limitations of Inline Function in C Merge and Merge sort with example in C Do-While Loop in C For Loop in C While-Loop in C Difference between while and do-while loop in C Array Of Structures in C Data Structures And Algorithms in C Types Of Structures In C How to Avoid Structure Padding in C Use of Structure in C Do WHILE LOOP in C Programming Examples For Loop in C Programming Examples Entry Control Loop in C Exit control loop in C Infinite loop in C Nested loop in C pow() function in C String Handling functions in C Prime Number code in C Factorial Program in C using For Loop Factorial Program in C Using While Loop Fibonacci Series in C Using For Loop Fibonacci series in C using while loop Prime Number Program in C using for Loop While Loop in C programming examples Built-in functions in C Assert() Function C vs Java Strings Call Back Function in Embedded C Else If Ladder fgets() function Ftell() Function getc() function getch() function gets() function Heap Sort Nested if-else statement Pi() Function Positioning of file Write() function abs() function in C Attributes in C C program to find factorial of a number using Recursion Ferror() in c fopen() function in C Fibonacci series program in C using Recursion Formatted Input and output function in C Snake Game in C User Defined Functions in C Beep() function in C Cbrt() function in C Hook() function in C Isalnum() function in C C Program to find the Roots of a Quadratic Equation C Switch Statements Difference between rand() and srand() function in C Difference between while and for loop in C Doubly Linked list in C Example of Iteration in C How to use atoi() function in C How to use floor() function in C How to use sine() function in C How to use Typedef Struct in C Integer Promotions in C C Program Swap Numbers in cyclic order Using Call by Reference C Program to Find Largest Number Using Dynamic Memory Allocation C Program to Find the Largest Number using Ternary Operator C/C++ Program to Find the Size of int, float, double and char Find the Largest Three Distinct Elements in an Array using C/C++ Loop Questions in C Modulus on Negative Numbers in C Multiplication table program in C using For loop Nested Loops in C Programming Examples C Program for Mean and Median of an Unsorted Array Results of Comparison Operations in C and C++ Reverse a Stack using Recursion in C Simple hash() function in C strcat() Function in C Sum of N numbers in C using For loop Use of free() function in C Write a program that produces different results in C and C++ C Function Argument and Return Values Keywords in C Bank management system in C Calendar application in C Floor() Function in C Free() Function in C How to delete a file in C How to move a text in C Remove an element from an array in C Unformatted input() and output() function in C What are linker and loader in C SJF Scheduling Program in C Socket Programming in C Structure in C Tower of Hanoi in C Union Program in C Variable Declaration in C What is Linked List in C While Loop Syntax in C fork() in C GCD program in C Branching Statements in C Comma Operator in C Control statement in C Double Specifier in C How to create a binary file in C Long int in C Palindrome Number in C Pure Virtual Function in C Run Time Polymorphism in C Types of Array in C Types of Function in C What is a buffer in C What is required in each C Program Associativity of Operators in C Bit Stuffing Program in C Actual and Formal Parameters Addition of two Numbers in C Advantages of function in C Arithmetic Progression Program in C Binomial Coefficient Program in C Difference between Array and List in C Diffie-Hellman Algorithm in C How to convert a number to words in C How to convert a string to hexadecimal in C Difference between If and Switch Statement in C C and C++ Binary Files C program that does not Suspend when Ctrl+Z is Pressed Different ways to Declare the Variable as Constant in C Range of Int in C C Program to find the size of a File FIFO Example in the C Language For loop in C Programming GCD program of two numbers in C GPA Calculator in C How to Calculate Time Complexity in C How to include graphics.h in C How to measure time taken by a function in C How to return a Pointer from a Function in C What is the main in C Addition of Matrix in C Booleans in C C Program for Extended Euclidean algorithms C Program of Fencing the Ground Ceil and Floor in C Compound Interest Program in C Displaying Array in C Distance Vector Routing Protocol Program in c Dos.h Header File in C Language DSA Program in C Explain the two-way selection in C Fee Management System in C File Operations in C Malloc function in C Multiplication Table in C Simple Programs in C Language tolower() Function in C Type Conversion in the C Why does sizeof(x++) not Increment x in C Advantages of Dynamic Memory Allocation in C Armstrong Number in C Assignment Operator Program in C Banker’s Algorithm in C Binary Search in C with Best and Worst Time Complexity Caesar Cipher Program in C Call by Value and Call by Reference in C Conditional Operator in C CRC Program in C Deadlock Detection Program in C Decimal to Binary in C Difference between If Else and Nested If Else in C Difference between Pre-increment and Post-increment in C Difference between Scope and Lifetime in C Evaluation of Arithmetic Expression in C Explain the Increment and Decrement Operators in C Fseek Function in C Functions in C How to Find Square Free Numbers in C Length of an Array Function in C OpenGL in C Projects on C language in 2023 Purpose of a Function Prototype in C Stdio.h in C Two-Dimensional array in C What is String Comparison in C C Compilers for Windows Functions and Recursion in C How to Declare Boolean in C How to Declare Character in C How to Round up a number in C How to use strlen() in C Pointer Declaration in C Algorithm for String Palindrome in C C Program to find ASCII value of a character Constant Pointer in C How to find string length in C using strlen() function Implicit and Explicit in C Indirect Recursion in C Input and Output functions in C isupper() in C Jump Statement in C Lifetime of a Variable in C Linker Error in C Language Numeric Constant in C Size of Pointer in C Square Root in C Language Static and Dynamic Memory allocation String Declaration in C Strong Number in C Symmetric Matrix in C Types of C Tokens What is a Size of Pointer in C What is Increment and Decrement Operator in C 1 2 3 4 Series Program in C Advantages and Disadvantages of C Language C Program for Polynomial Addition C Program to Count the Number of Vowels in a String C Programming Errors and Solutions Compilation Errors in C Complex C Programs Difference between Argument and Parameter in C Difference between char s[] and char *s in C Evaluation of Postfix Expression Using Stack in C Find Leftmost and Rightmost Set Bit of a Number fprintf and fscanf in C Introduction to Dynamic Array in C Print Address in C Realloc function in C Ternary Operators in C Types of Tokens in C with Examples Difference between Static and Dynamic Memory Allocation in C Addition Program in C Array Definition in C Array of Pointers in C Arrow Operator in C Average of Two Numbers in C Binary to Decimal in C Binary to Octal in C BREAK STATEMENT in C C Programming Operators Questions C Programs Asked in Interview Calculator Program in C C Program to Read and Print an Employee's Detail Using Structure Bubble Sort Algorithm in C C Program to Find Area and Perimeter of Circle C Program to Check Whether a Given Number is Even or Odd C in Roman Numerals C Program to Make a Simple Calculator Using Switch Case Insertion Sort Program in C How to take input in string in C GCC Conflicting Types in C Function Definition in C Format Specifier for Hexadecimal in C Flowchart in C Float in C Fizzbuzz Implementation in C Conditional Statement in C Conio.h functions list in C Constants in C Dynamic Array in C Decision Making Statements in C Continue Statement in C Creation of Thread in C DFS Algorithm in C Difference between parameter and arguments in C Dijkstra's Algorithm in C Leap Year Program in C Jump Statements in C Modulus Operator in C Memory Allocation in C Simple Interest Program in C Reverse Array in C Recursive Function in C Queue in C Printing Pascal’s Triangle in C Preprocessor Directives in C Perror() in C Perfect Number in C Programming Language Parameter Passing Techniques in C Pascal Triangle in C Patterm Program in C Affine cipher in C Dereferencing pointer in C Internal static variable vs External static variables in C Difference between exit(0) and exit(1) in C Booth's Algorithm in C Condition Control Statements in C Double Specifier in C Dynamic variables in C How to print alphabets in C How to print char array in c Order of Evaluation in C Order of Operations in C Semantic Error in C Size of String Variable in C SJF PREEMPTIVE SCHEDULING PROGRAM C: Tree in C Arithmetic Progression Program in C Array, Declaring Arrays, and Array Initialization ARRAYS IN C Assert() Function in c Atoi in C Banker’s Algorithm in C Bar3d() function in C Graphics Beep function in c Bigint (BIG INTEGERS) in C with Example Builtin functions of GCC compiler Fibonacci series in C Priority Queue in C 2D ARRAY IN C 7 Best IDEs for C/C++ Developers in 2022 Addition of Two Numbers in C Advantages and Disadvantages of C Language Advantages of Function in C Algorithm for String Palindrome in C

Calendar application in C

Introduction to the calendar application

We all are familiar with the calendar. It plays a crucial role in our daily life. We run toward the calendar whenever we want to know today's date or what day it is. We also run towards the calendar when we want to check holidays and vacations. Nowadays, everything has been digitalized. We barely use physical calendars, but we all have at least one calendar at home. We use our mobile phone to check the date and days, and nowadays it is also visible on the lock screen. Mobile phones and desktops consist of the calendar application from the very beginning. When everything was not digitalized as there were still calendar applications, today we will understand how calendar apps can be made by just using the c language. Let us understand the features and the blueprint of the whole application.

Features of the calendar application: here, we will make a calendar for any specific year, and the year will be taken as per the user's choice. Suppose the user enters 2000, then we will make a calendar for 2000.

We have to specify months and days accordingly, which should be in proper calendar format. So we have to take care of the user interface and the logic behind it. So let's code.

Code for the calendar application

calender_app.c

#include<stdio.h>
#define TRUE    1
#define FALSE   0


int days_in_months[]={0,31,28,31,30,31,30,31,31,30,31,30,31};
char *months[]=
{
	" ",
	"\n\n\nJanuary( jan)", // this will show the januray month name at the top of the dates
	"\n\n\nFebruary (feb)",// this will show the February month name at the top of the dates
	"\n\n\nMarch (march) ",// this will show the march month name at the top of the dates
	"\n\n\nApril (april)",// this will show the april month name at the top of the dates
	"\n\n\nMay(may)",// this will show the may month name at the top of the dates
	"\n\n\nJune (june)",// this will show the June month name at the top of the dates.
	"\n\n\nJuly ( july) ",// this will show the July month name at the top of the dates.
	"\n\n\nAugust (august)",// this will show the august month name at the top of the dates
	"\n\n\nSeptember (sept)",// this will show the september month name at the top of the dates
	"\n\n\nOctober (October) ",// this will show the October month name at the top of the dates.
	"\n\n\nNovember ( nov)",// this will show the November month name at the top of the dates
	"\n\n\nDecember (dec )"// this will show the December month name at the top of the dates.
};




int inputyear(void)
{
	int year_entered;
	
	printf("Please enter a year (example: 2000 ) : "); 
	scanf("%d", &year_entered);// this is for taking the year input from the user
	return year_entered;
}


int determine_day_code(int year_entered)
{
	int day_code;
	int d1, d2, d;
	
	d = (year_entered - 1.)/ 4.0;
	d1 = (year_entered - 1.)/ 100.;
	d2 = (year_entered - 1.)/ 400.;
	day_code = (year_entered + d - d1 + d2) %7; //this is for the calculations of proper day code
	return day_code;
}




int determine_leap_year(int year_entered)
{
	if(year_entered% 4 == FALSE && year_entered%100 != FALSE || year_entered%400 == FALSE)
	{
		days_in_months[2] = 29;
		return TRUE;
	}
	else
	{
		days_in_months[2] = 28;
		return FALSE;
	}
}


void calendar_application(int year_entered, int daycode)
{
	int month, day;
	for ( month = 1; month <= 12; month++ )
	{
		printf("%s", months[month]);
		printf("\n\nSun  Mon  Tue  Wed  Thu  Fri  Sat\n" );
		
		// this is to Correct the position for the first date of the calendar_application
		for ( day = 1; day <= 1 + daycode * 5; day++ )
		{
			printf(" ");
		}
		
		// this is for Printing all the dates for one month of the calendar_application
		for ( day = 1; day <= days_in_months[month]; day++ )
		{
			printf("%2d", day );
			
			//this is for checking. Is the day before Sat? If yes, then executed Else, start next line Sun will be executed
			if ( ( day + daycode ) % 7 > 0 )
				printf("   " );
			else
				printf("\n " );
		}
			//this is for Setting a position for next month in the application
			daycode = ( daycode + days_in_months[month] ) % 7;
	}
}


int main(void)
{
	int year_entered, daycode, leapyear;
	
	year_entered = inputyear();
	daycode = determine_day_code(year_entered);
	determine_leap_year(year_entered);
	calendar_application(year_entered, daycode);
	printf("\n");
}

Output: here, only a few months are shown in the output. If you run the code above, you can witness that it will show you the calendar from January to December, which will be in proper format as shown below. Please check the output attached below.

Calendar application in c

Explanation: Let us understand the code part by part for better understanding.

Declaring the total number of days as it stays fix

int days_in_months[]={0,31,28,31,30,31,30,31,31,30,31,30,31};

Here we have provided the total number of days for each month, we know no matter what this will remain fixed for every year, but there is a problem as you know February is different from the rest of the month, there are two reasons first it has mostly 28 days second sometimes it has 29 days if the year is a leap year, we need to check whether the year entered by the user is a leap year or not, if yes then we have to add 29 days in February instead of 28, but here we have given 28 as most of the times it remains 28.

Checking for leap year :

int determine_leap_year(int year_entered)
{
	if(year_entered% 4 == FALSE && year_entered%100 != FALSE || year_entered%400 == FALSE)
	{
		days_in_months[2] = 29;
		return TRUE;
	}
	else
	{
		days_in_months[2] = 28;
		return FALSE;
	}
}

So once the user enters the year's value, we call for this function, and then we check whether the year is divisible by particular values. If it results true, we manipulate the second value of the days_in_months array, and if it turns out to be false, then we let it be 28 as the year is not a leap year. So this is how we deal with the problem of the total number of days in the leap year, and we produce a calendar for the leap year.

Printing the day code( name of weekdays )

// this is for Printing all the dates for one month of the calendar_application
		for ( day = 1; day <= days_in_months[month]; day++ )
		{
			printf("%2d", day );
			
			//this is for checking. Is the day before Sat? If yes, then executed Else, start next line Sun will be executed
			if ( ( day + daycode ) % 7 > 0 )
				printf("   " );
			else
				printf("\n " );
		}
			//this is for setting a position for next month in the application
			daycode = ( daycode + days_in_months[month] ) % 7;
	}

So we all know there are a total of 7 days in a week. They follow from Sunday to Saturday, and we must manage proper day codes for each day. It is also a crucial step that must be done carefully. We check the last day of the previous month, and then it is divided by 7 to get day codes for the next month. It is a conventional method to produce the correct day code; this same method is used in various aptitude problems to find the correct day code of that particular day. It is a mathematical calculation.

Lastly, we call every function and thus, it produces the required calendar.

year_entered = inputyear();
	daycode = determine_day_code(year_entered);
	determine_leap_year(year_entered);
	calendar_application(year_entered, daycode);
	printf("\n");

We ask for the year from the user, and when a user enters it, we pass the year's value in our functions, and the calendar is produced.

So, this was brief about our calendar application, which can also be added to the resume to show proficiency in the C language. We can even build an app by this logic of calendar generation by improving the user interface and adding a few more functionalities to this project.