fundamentals of C programming

C language Tutorial with programming approach for beginners and professionals, helps you to understand the C language tutorial easily. Our C tutorial explains each topic with programs.

The C Language is developed by Dennis Ritchie in 1972 for creating system applications that directly interact with the hardware devices such as drivers, kernels, etc.

C programming is considered as the base for other programming languages, that is why it is known as mother language.

It can be defined by the following ways:

1. Mother language
2. System programming language
3. Procedure-oriented programming language
4. Structured programming language
5. Mid-level programming language

Learn the Basics:-

• Hello, World!

Most students of programming languages, start from the famous 'Hello World' code. This program prints 'Hello World' when executed. This simple example tries to make understand that how C programs are constructed and executed.

#include <stdio.h>

int main() {
   printf("Hello World!");
   return 0;
}

The output of the program should be −

Hello World!

• Variables and Types

Let’s learn about variables and data types in C Programming. We will first look at Variables in C; Variables are used to store the value during the execution of a program. The name itself means, the value of variable can be changed hence the name “Variable“. The variables are stored in Main Memory i.e. RAM (size depending on the data type). In C Programming we always have to declare variable before we can use them. Note that the space is allocated to variable in memory during execution or run-time.

C is a strongly typed language. What this means it that, the type of a variable cannot be changed. Suppose we declared an integer type variable so we cannot store character or a decimal number in that variable.

There are set of rules to be followed while declaring variables and data types in C Programming:

• The 1st letter should be alphabet.
• Variables can be combination of alphabets and digits.
• Underscore (_) is the only special character allowed.
• Variables can be written in both Uppercase and Lowercase or combination of both.
• Variables are Case Sensitive.
• No Spaces allowed between Characters.
• Variable name should not make use to the C Reserved Keywords.
• Variable name should not start with a number.

Variables and Data Types in C

Data Types in C Programming Language

EXAMPLE 1: Integer Variable in C

#include <stdio.h>

void main()
{
    int i = 10;
    printf("This is my integer: %d \n", i);
}

The %d is to tell printf() function to format the integer i as a decimal number. The output from this program would be This is my integer: 10.

EXAMPLE 2: Float Variable in C

#include <stdio.h>

void main()
{
    float f = 3.1415;
    printf("This is my float: %f \n", f);
}

The %f is to tell printf() function to format the float variable f as a decimal floating number. The output from this program would be This is my float: 3.1415. Now if we want to see only the first 2 numbers after the floating point, we would have to modify printf() function call to be as given below:

 printf("This is my shorter float: %.2f \n", f);

After replacing printf function in a given example. The output from this program would be This is my float: 3.14.

EXAMPLE 3: Character Variable in C

#include <stdio.h>

void main()
{
    char c;
    c = 'b';
    printf("This is my character: %c \n", c);
}

The %c is to tell printf() function to format the variable “c” as a character. The output from this program would be This is my character: b.

Data types in C Programming

All the data types defined by C are made up of units of memory called bytes. On most computer architectures a byte is made up of eight bits, each bit stores a one or a zero. These eight bits with two states give 256 combinations (2⁸). So an integer which takes up four bytes can store a number between 0 to 4,294,967,295 (0 and 2³²). However, integer variables use the first bit to store whether the number is positive or negative so their value will be between -2,147,483,648 and + 2,147,483,647.

As we mentioned, there are eight basic data types defined in the C language. Five types for storing integers of varying sizes and three types for storing floating point values (values with a decimal point). C doesn’t provide a basic data type for text. Text is made up of individual characters and characters are represented by numbers. In the last example we used one of the integer types: int. This is the most commonly used type in the C language.

Data Type	Size	Value Range
char	1 byte	-128 to 127 or 0 to 255
unsigned char	1 byte	0 to 255
signed char	1 byte	-128 to 127
int	2 or 4 bytes	-32,768 to 32,767 or -2,147,483,648 to 2,147,483,647
unsigned int	2 or 4 bytes	0 to 65,535 or 0 to 4,294,967,295
short	2 byte	-32,768 to 32,767
unsigned short	2 byte	0 to 65,535
long	4 byte	-2,147,483,648 to 2,147,483,647
unsigned long	4 byte	0 to 4,294,967,295

The char data type is usually one byte, it is so called because they are commonly used to store single characters. The size of the other types is dependent on machine. Most desktop machines are “32-bit”, this refers to the size of data that they are designed for processing. On “32-bit” machines the int data type takes up 4 bytes (232). The short is usually smaller, the long can be larger or the same size as an int and finally the long long is for handling very large numbers.

The type of variable you use generally doesn’t have a big impact on the speed or memory usage of your application. Unless you have a special need you can just use int variables. We will try to point out the few different cases like. A decade ago, most machines had 16-bit processors, this limited the size of int variables to 2 bytes. At the time, short variables were usually also 2 bytes and long would be 4 bytes. Nowadays, with 32-bit machines, the default type (int) is usually large enough to satisfy what used to require a variable of type long. The long long type was introduced more recently to handle very large numeric values.

EXAMPLE 3: Calculate Size of Data type on Your Machine

To find out the size of each data type on your machine compile and run this program. It uses one new language construct sizeof(). This tells us how many bytes a data type takes up.

#include <stdio.h>

int main()
{
  printf("sizeof(char) == %d\n", sizeof(char));
  printf("sizeof(short) == %d\n", sizeof(short));
  printf("sizeof(int) == %d\n", sizeof(int));
  printf("sizeof(long) == %d\n", sizeof(long));
  printf("sizeof(long long) == %d\n", sizeof(long long));

  return 0;
}

The output from this program would be:

Output of Sizeof Data Types

Some computers are better at handling really big numbers, so the size of the data types will be bigger on these machines. Now we know most basic building blocks i.e. variables and data types in C Programming. In next lesson we will covers Operators in C Programming which allows us to solve many computing issues while programming.

• conditions

Decision Making

In life, we all have to make decisions. In order to make a decision we weigh out our options and so do our programs.

Here is the general form of the decision making structures found in C.

int target = 10;
if (target == 10) {
    printf("Target is equal to 10");
}

The if statement

The if statement allows us to check if an expression is true or false, and execute different code according to the result.

To evaluate whether two variables are equal, the == operator is used, just like in the first example.

Inequality operators can also be used to evaluate expressions. For example:

int foo = 1;
int bar = 2;

if (foo < bar) {
    printf("foo is smaller than bar.");
}

if (foo > bar) {
    printf("foo is greater than bar.");
}

We can use the else keyword to exectue code when our expression evaluates to false.

int foo = 1;
int bar = 2;

if (foo < bar) {
    printf("foo is smaller than bar.");
} else {
    printf("foo is greater than bar.");
}

Sometimes we will have more than two outcomes to choose from. In these cases, we can "chain" multiple if else statements together.

int foo = 1;
int bar = 2;

if (foo < bar) {
    printf("foo is smaller than bar.");
} else if (foo == bar) {
    printf("foo is equal to bar.");
} else {
    printf("foo is greater than bar.");
}

You can also nest if else statements if you like.

int peanuts_eaten = 22;
int peanuts_in_jar = 100;
int max_peanut_limit = 50;

if (peanuts_in_jar > 80) {
    if (peanuts_eaten < max_peanut_limit) {
        printf("Take as many peanuts as you want!\n");
    }
} else {
    if (peanuts_eaten > peanuts_in_jar) {
        printf("You can't have anymore peanuts!\n");
    }
    else {
        printf("Alright, just one more peanut.\n");
    }
}

Two or more expressions can be evaluated together using logical operators to check if two expressions evaluate to true together, or at least one of them. To check if two expressions both evaluate to true, use the AND operator &&. To check if at least one of the expressions evaluate to true, use the OR operator ||.

int foo = 1;
int bar = 2;
int moo = 3;

if (foo < bar && moo > bar) {
    printf("foo is smaller than bar AND moo is larger than bar.");
}

if (foo < bar || moo > bar) {
    printf("foo is smaller than bar OR moo is larger than bar.");
}

The NOT operator ! can also be used likewise:

int target = 9;
if (target != 10) {
    printf("Target is not equal to 10");
}

•  loops

In programming, a loop is used to repeat a block of code until the specified condition is met.

C programming has three types of loops:

1. for loop
2. while loop
3. do...while loop

for loops:-

We will learn about for loop in this tutorial. In the next tutorial, we will learn about while and do...while loop.

The syntax of the for loop is:

for (initializationStatement; testExpression; updateStatement)
{
    // statements inside the body of loop
}

---

How for loop works?

• The initialization statement is executed only once.
• Then, the test expression is evaluated. If the test expression is evaluated to false, the for loop is terminated.
• However, if the test expression is evaluated to true, statements inside the body of for loop are executed, and the update expression is updated.
• Again the test expression is evaluated.

This process goes on until the test expression is false. When the test expression is false, the loop terminates.

Example 1: for loop

// Print numbers from 1 to 10
#include <stdio.h>

int main() {
  int i;

  for (i = 1; i < 11; ++i)
  {
    printf("%d ", i);
  }
  return 0;
}

Output

1 2 3 4 5 6 7 8 9 10

Example 2: for loop
// Program to calculate the sum of first n natural numbers
// Positive integers 1,2,3...n are known as natural numbers

#include <stdio.h>
int main()
{
    int num, count, sum = 0;

    printf("Enter a positive integer: ");
    scanf("%d", &num);

    // for loop terminates when num is less than count
    for(count = 1; count <= num; ++count)
    {
        sum += count;
    }

    printf("Sum = %d", sum);

    return 0;
}

While loops:-

The syntax of the while loop is:

while (testExpression) 
{
    // statements inside the body of the loop 
}

---

How while loop works?

• The while loop evaluates the test expression inside the parenthesis ().
• If the test expression is true, statements inside the body of while loop are executed. Then, the test expression is evaluated again.
• The process goes on until the test expression is evaluated to false.
• If the test expression is false, the loop terminates (ends).

Example 1: while loop

// Print numbers from 1 to 5

#include <stdio.h>
int main()
{
    int i = 1;
    
    while (i <= 5)
    {
        printf("%d\n", i);
        ++i;
    }

    return 0;
}

Output

1
2
3
4
5

do...while loop:

The do..while loop is similar to the while loop with one important difference. The body of do...while loop is executed at least once. Only then, the test expression is evaluated.

The syntax of the do...while loop is:
do
{
   // statements inside the body of the loop
}
while (testExpression);


How do...while loop works?

The body of do...while loop is executed once. Only then, the test expression is evaluated.
If the test expression is true, the body of the loop is executed again and the test expression is evaluated.
This process goes on until the test expression becomes false.
If the test expression is false, the loop ends.



Example 2: do...while loop
// Program to add numbers until the user enters zero

#include <stdio.h>
int main()
{
    double number, sum = 0;

    // the body of the loop is executed at least once
    do
    {
        printf("Enter a number: ");
        scanf("%lf", &number);
        sum += number;
    }
    while(number != 0.0);

    printf("Sum = %.2lf",sum);

    return 0;
}

Output
Enter a number: 1.5
Enter a number: 2.4
Enter a number: -3.4
Enter a number: 4.2
Enter a number: 0
Sum = 4.70

c break & continue statement

C break

The break statement ends the loop immediately when it is encountered. Its syntax is:

break;

The break statement is almost always used with if...else statement inside the loop.

---

How break statement works?

---

Example 1: break statement

// Program to calculate the sum of a maximum of 10 numbers
// If a negative number is entered, the loop terminates

# include <stdio.h>
int main()
{
    int i;
    double number, sum = 0.0;

    for(i=1; i <= 10; ++i)
    {
        printf("Enter a n%d: ",i);
        scanf("%lf",&number);

        // If the user enters a negative number, the loop ends
        if(number < 0.0)
        {
            break;
        }

        sum += number; // sum = sum + number;
    }

    printf("Sum = %.2lf",sum);
    
    return 0;
}

Output

Enter a n1: 2.4
Enter a n2: 4.5
Enter a n3: 3.4
Enter a n4: -3
Sum = 10.30

This program calculates the sum of a maximum of 10 numbers. Why a maximum of 10 numbers? It's because if the user enters a negative number, the break statement is executed. This will end the for loop, and the sum is displayed.

In C, break is also used with the switch statement. This will be discussed in the next tutorial.

---

C continue

The continue statement skips the current iteration of the loop and continues with the next iteration. Its syntax is:

continue;

The continue statement is almost always used with the if...else statement.

---

How continue statement works?

---

Example 2: continue statement

// Program to calculate the sum of a maximum of 10 numbers
// Negative numbers are skipped from the calculation

# include <stdio.h>
int main()
{
    int i;
    double number, sum = 0.0;

    for(i=1; i <= 10; ++i)
    {
        printf("Enter a n%d: ",i);
        scanf("%lf",&number);

        if(number < 0.0)
        {
            continue;
        }

        sum += number; // sum = sum + number;
    }

    printf("Sum = %.2lf",sum);
    
    return 0;
}

Output

Enter a n1: 1.1
Enter a n2: 2.2
Enter a n3: 5.5
Enter a n4: 4.4
Enter a n5: -3.4
Enter a n6: -45.5
Enter a n7: 34.5
Enter a n8: -4.2
Enter a n9: -1000
Enter a n10: 12
Sum = 59.70

C switch Statement

The switch statement allows us to execute one code block among many alternatives.

You can do the same thing with the if...else..if ladder. However, the syntax of the switch statement is much easier to read and write.

---

Syntax of switch...case

switch (expression)
​{
    case constant1:
      // statements
      break;

    case constant2:
      // statements
      break;
    .
    .
    .
    default:
      // default statements
}

How does the switch statement work?

The expression is evaluated once and compared with the values of each case label.

• If there is a match, the corresponding statements after the matching label are executed. For example, if the value of the expression is equal to constant2, statements after case constant2: are executed until break is encountered.
• If there is no match, the default statements are executed.

If we do not use break, all statements after the matching label are executed.

By the way, the default clause inside the switch statement is optional.

---

Example: Simple Calculator

// Program to create a simple calculator
#include <stdio.h>

int main() {
    char operator;
    double n1, n2;

    printf("Enter an operator (+, -, *, /): ");
    scanf("%c", &operator);
    printf("Enter two operands: ");
    scanf("%lf %lf",&n1, &n2);

    switch(operator)
    {
        case '+':
            printf("%.1lf + %.1lf = %.1lf",n1, n2, n1+n2);
            break;

        case '-':
            printf("%.1lf - %.1lf = %.1lf",n1, n2, n1-n2);
            break;

        case '*':
            printf("%.1lf * %.1lf = %.1lf",n1, n2, n1*n2);
            break;

        case '/':
            printf("%.1lf / %.1lf = %.1lf",n1, n2, n1/n2);
            break;

        // operator doesn't match any case constant +, -, *, /
        default:
            printf("Error! operator is not correct");
    }

    return 0;
}

Output

Enter an operator (+, -, *,): -
Enter two operands: 32.5
12.4
32.5 - 12.4 = 20.1

• Arrays

Array is a collection of homogenous data, arranged in sequential format. Learning the concept of arrays in C is very important as it is the basic data structure. Here, in this section, we shall look into some very useful array programs to give you insight of how C programming language deals with arrays.

Single Array Programs

These programs are basic and involves only a single array variable. We shall learn how to handle array variable in different situation.

1.A program to print an array

#include <stdio.h>

int main() {
   int array[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int loop;

   for(loop = 0; loop < 10; loop++)
      printf("%d ", array[loop]);
      
   return 0;
}

The output should look like this −

1 2 3 4 5 6 7 8 9 0

• 
  

2.A program to print an array in reverse order

#include <stdio.h>

int main() {
   int array[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int loop;

   for(loop = 9; loop >= 0; loop--)
      printf("%d ", array[loop]);
      
   return 0;
}

The output should look like this −

0 9 8 7 6 5 4 3 2 1

3.Program to calculate sum of an array

#include <stdio.h>

int main() {
   int array[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int sum, loop;

   sum = 0;
   
   for(loop = 9; loop >= 0; loop--) {
      sum = sum + array[loop];      
   }

   printf("Sum of array is %d.", sum);   

   return 0;
}

The output should look like this −
Average of array values is 4.50

4.Program to calculate average of an array

#include <stdio.h>

int main() {
   int array[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int sum, loop;
   float avg;

   sum = avg = 0;
   
   for(loop = 0; loop < 10; loop++) {
      sum = sum + array[loop];
   }
   
   avg = (float)sum / loop;
   printf("Average of array values is %.2f", avg);   
   
   return 0;
}

The output should look like this −

Average of array values is 4.50

5.Program to find the largest element of an array

• 
  

#include <stdio.h>

int main() {
   int array[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int loop, largest;

   largest = array[0];
   
   for(loop = 1; loop < 10; loop++) {
      if( largest < array[loop] ) 
         largest = array[loop];
   }
   
   printf("Largest element of array is %d", largest);   
   
   return 0;
}

The output should look like this −

Largest element of array is 9

6.Program to find the second largest element of an array

#include <stdio.h>

int main() {
   int array[10] = {101, 11, 3, 4, 50, 69, 7, 8, 9, 0};
   int loop, largest, second;

   if(array[0] > array[1]) {
      largest = array[0];
      second  = array[1];
   } else {
      largest = array[1];
      second  = array[0];
   }

   for(loop = 2; loop < 10; loop++) {
      if( largest < array[loop] ) {
         second = largest;
         largest = array[loop];
      } else if( second < array[loop] ) {
         second =  array[loop];
      }
   }

   printf("Largest - %d \nSecond - %d \n", largest, second);   

   return 0;
}

The output should look like this −

Largest - 101
Second - 69

7.Program to find the smallest element of an array

#include <stdio.h>

int main() {
   int array[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int loop, smallest;

   smallest = array[0];
   
   for(loop = 1; loop < 10; loop++) {
      if( smallest > array[loop] ) 
         smallest = array[loop];
   }
   
   printf("Smallest element of array is %d", smallest);   
   
   return 0;
}

The output should look like this −

Smallest element of array is 0

#include <stdio.h>

int main() {
   int array[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int loop, smallest;

   smallest = array[0];
   
   for(loop = 1; loop < 10; loop++) {
      if( smallest > array[loop] ) 
         smallest = array[loop];
   }
   
   printf("Smallest element of array is %d", smallest);   
   
   return 0;
}

The output should look like this −

Smallest element of array is 0

Multi Array Programs

These programs involve more than one array. This section should give you some easy techniques to handle more than one array variables in a program.

1.Program to copy an array to another array

#include <stdio.h>

int main() {
   int original[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int copied[10];
   int loop;
   
   for(loop = 0; loop < 10; loop++) {
      copied[loop] = original[loop];
   }
   printf("original -> copied \n");
   
   for(loop = 0; loop < 10; loop++) {
      printf("   %2d        %2d\n", original[loop], copied[loop]);
   }

   return 0;
}

The output should look like this −

original -> copied
    1         1
    2         2
    3         3
    4         4
    5         5
    6         6
    7         7
    8         8
    9         9
    0         0

• 
  

2.Program to copy an array to another array in reverse

#include <stdio.h>

int main() {
   int original[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
   int copied[10];
   int loop, count;
   
   count = 9;
   
   for(loop = 0; loop < 10; loop++) {
      copied[count] = original[loop];
      count--;
   }
      
   printf("original -> copied \n");
   
   for(loop = 0; loop < 10; loop++) {
      printf("   %2d        %2d\n", original[loop], copied[loop]);
   }

   return 0;
}

The output should look like this −

original -> copied
    1         0
    2         9
    3         8
    4         7
    5         6
    6         5
    7         4
    8         3
    9         2
    0         1

• 
  

3.Program to divide one array into two arrays

#include <stdio.h>

int main() {
   int array[10] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
   int even[10], odd[10];
   int loop, e, d;
   
   e = d = 0;
   
   for(loop = 0; loop < 10; loop++) {
      if(array[loop]%2 == 0) {
         even[e] = array[loop];
         e++;
      } else {
         odd[d] = array[loop];
         d++;
      }
   }

   printf(" original -> ");
   
   for(loop = 0; loop < 10; loop++)
      printf(" %d", array[loop]);
       
   printf("\n even -> ");
   
   for(loop = 0; loop < e; loop++)
      printf(" %d", even[loop]);   

   printf("\n odd -> ");
   
   for(loop = 0; loop < d; loop++)
      printf(" %d", odd[loop]);   

   return 0;
}

The output should look like this −

 original ->  0 1 2 3 4 5 6 7 8 9
 even ->  0 2 4 6 8
 odd ->  1 3 5 7 9

4.Program to concatenate arrays

#include <stdio.h>

int main() {
   int array[10];
   int even[5] = {0, 2, 4, 6, 8};
   int odd[5]  = {1, 3, 5, 7, 9};
   
   int loop, index, e_len, o_len;
   
   e_len = o_len = 5;
   
   index = 0;
 
   for(loop = 0; loop < e_len; loop++) {
      array[index] = even[loop];
      index++;
   }
 
   for(loop = 0; loop < o_len; loop++) {
      array[index] = odd[loop];
      index++;
   }

   printf("\nEven -> ");
   
   for(loop = 0; loop < e_len; loop++)
      printf(" %d", even[loop]);
   
   printf("\nOdd  -> ");
   
   for(loop = 0; loop < o_len; loop++)
      printf(" %d", odd[loop]);

   printf("\nConcat -> ");
   
   for(loop = 0; loop < 10; loop++)
      printf(" %d", array[loop]);

   return 0;
}

The output should look like this −

Even ->  0 2 4 6 8
Odd  ->  1 3 5 7 9
Concat ->  0 2 4 6 8 1 3 5 7 9

C Multidimensional Arrays:-

In this tutorial, you will learn to work with multidimensional arrays (two-dimensional and three-dimensional arrays) with the help of examples.

In C programming, you can create an array of arrays. These arrays are known as multidimensional arrays. For example,

float x[3][4];

Here, x is a two-dimensional (2d) array. The array can hold 12 elements. You can think the array as a table with 3 rows and each row has 4 columns.

Similarly, you can declare a three-dimensional (3d) array. For example,

float y[2][4][3];

Here, the array y can hold 24 elements.

---

Initializing a multidimensional array

Here is how you can initialize two-dimensional and three-dimensional arrays:

---

Initialization of a 2d array

// Different ways to initialize two-dimensional array

int c[2][3] = {{1, 3, 0}, {-1, 5, 9}};
         
int c[][3] = {{1, 3, 0}, {-1, 5, 9}};
                
int c[2][3] = {1, 3, 0, -1, 5, 9};

---

Initialization of a 3d array

You can initialize a three-dimensional array in a similar way like a two-dimensional array. Here's an example,

int test[2][3][4] = {
    {{3, 4, 2, 3}, {0, -3, 9, 11}, {23, 12, 23, 2}},
    {{13, 4, 56, 3}, {5, 9, 3, 5}, {3, 1, 4, 9}}};

---

Example 1: Two-dimensional array to store and print values

// C program to store temperature of two cities of a week and display it.
#include <stdio.h>
const int CITY = 2;
const int WEEK = 7;
int main()
{
  int temperature[CITY][WEEK];

  // Using nested loop to store values in a 2d array
  for (int i = 0; i < CITY; ++i)
  {
    for (int j = 0; j < WEEK; ++j)
    {
      printf("City %d, Day %d: ", i + 1, j + 1);
      scanf("%d", &temperature[i][j]);
    }
  }
  printf("\nDisplaying values: \n\n");

  // Using nested loop to display vlues of a 2d array
  for (int i = 0; i < CITY; ++i)
  {
    for (int j = 0; j < WEEK; ++j)
    {
      printf("City %d, Day %d = %d\n", i + 1, j + 1, temperature[i][j]);
    }
  }
  return 0;
}

Output

City 1, Day 1: 33
City 1, Day 2: 34
City 1, Day 3: 35
City 1, Day 4: 33
City 1, Day 5: 32
City 1, Day 6: 31
City 1, Day 7: 30
City 2, Day 1: 23
City 2, Day 2: 22
City 2, Day 3: 21
City 2, Day 4: 24
City 2, Day 5: 22
City 2, Day 6: 25
City 2, Day 7: 26

Displaying values: 

City 1, Day 1 = 33
City 1, Day 2 = 34
City 1, Day 3 = 35
City 1, Day 4 = 33
City 1, Day 5 = 32
City 1, Day 6 = 31
City 1, Day 7 = 30
City 2, Day 1 = 23
City 2, Day 2 = 22
City 2, Day 3 = 21
City 2, Day 4 = 24
City 2, Day 5 = 22
City 2, Day 6 = 25
City 2, Day 7 = 26

---

Example 2: Sum of two matrices

// C program to find the sum of two matrices of order 2*2

#include <stdio.h>
int main()
{
  float a[2][2], b[2][2], result[2][2];

  // Taking input using nested for loop
  printf("Enter elements of 1st matrix\n");
  for (int i = 0; i < 2; ++i)
    for (int j = 0; j < 2; ++j)
    {
      printf("Enter a%d%d: ", i + 1, j + 1);
      scanf("%f", &a[i][j]);
    }

  // Taking input using nested for loop
  printf("Enter elements of 2nd matrix\n");
  for (int i = 0; i < 2; ++i)
    for (int j = 0; j < 2; ++j)
    {
      printf("Enter b%d%d: ", i + 1, j + 1);
      scanf("%f", &b[i][j]);
    }

  // adding corresponding elements of two arrays
  for (int i = 0; i < 2; ++i)
    for (int j = 0; j < 2; ++j)
    {
      result[i][j] = a[i][j] + b[i][j];
    }

  // Displaying the sum
  printf("\nSum Of Matrix:");

  for (int i = 0; i < 2; ++i)
    for (int j = 0; j < 2; ++j)
    {
      printf("%.1f\t", result[i][j]);

      if (j == 1)
        printf("\n");
    }
  return 0;
}

Output

Enter elements of 1st matrix
Enter a11: 2;
Enter a12: 0.5;
Enter a21: -1.1;
Enter a22: 2;
Enter elements of 2nd matrix
Enter b11: 0.2;
Enter b12: 0;
Enter b21: 0.23;
Enter b22: 23;

Sum Of Matrix:
2.2     0.5
-0.9    25.0

---

Example 3: Three-dimensional array

// C Program to store and print 12 values entered by the user

#include <stdio.h>
int main()
{
  int test[2][3][2];

  printf("Enter 12 values: \n");

  for (int i = 0; i < 2; ++i)
  {
    for (int j = 0; j < 3; ++j)
    {
      for (int k = 0; k < 2; ++k)
      {
        scanf("%d", &test[i][j][k]);
      }
    }
  }

  // Printing values with proper index.

  printf("\nDisplaying values:\n");
  for (int i = 0; i < 2; ++i)
  {
    for (int j = 0; j < 3; ++j)
    {
      for (int k = 0; k < 2; ++k)
      {
        printf("test[%d][%d][%d] = %d\n", i, j, k, test[i][j][k]);
      }
    }
  }

  return 0;
}

Output

Enter 12 values: 
1
2
3
4
5
6
7
8
9
10
11
12

Displaying Values:
test[0][0][0] = 1
test[0][0][1] = 2
test[0][1][0] = 3
test[0][1][1] = 4
test[0][2][0] = 5
test[0][2][1] = 6
test[1][0][0] = 7
test[1][0][1] = 8
test[1][1][0] = 9
test[1][1][1] = 10
test[1][2][0] = 11
test[1][2][1] = 12

• Strings

Strings are actually one-dimensional array of characters terminated by a null character '\0'. Thus a null-terminated string contains the characters that comprise the string followed by a null.

The following declaration and initialization create a string consisting of the word "Hello". To hold the null character at the end of the array, the size of the character array containing the string is one more than the number of characters in the word "Hello."

char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};

If you follow the rule of array initialization then you can write the above statement as follows −

char greeting[] = "Hello";

In this section, we shall learn how to work with string C programming language. We have divided the examples in multiple sub-sections to have a better understanding of what we are doing −

Basic Programs

These programs made specially to understand the basics of strings in C. These program deals with string as an array of characters.

1.Program to print a string in C

#include <stdio.h>

int main() {
   char str[] = "Hello World";

   printf("%s\n", str);

   return 0;
}

Output

Output of this program should be −

Hello World

• 
  

2.Program to find string length without function in C

#include <stdio.h>

int main() {
   char s1[] = "TajMahal";
   int i = 0;
      
   while(s1[i] != '\0') {
      i++;
   }
   
   printf("Length of string '%s' is %d", s1, i);
   
   return 0;
}

Output

Output of this program should be −

Length of string 'TajMahal' is 8

3.Program to count character occurrent in C

#include<stdio.h>

int main() {
   char s[] = "TajMahal";     // String Given
   char ch = 'a';             // Character to count
 
   int i = 0;
   int count = 0;             // Counter
      
   while(s[i] != '\0') {
      if(s[i] == ch)
         count++;

      i++;
   }
   
   if(count > 0) {
      if(count == 1)
         printf("%c appears %d time in '%s'", ch, count, s);
      else
         printf("%c appears %d times in '%s'", ch, count, s);
   } else
      printf("%c did not appear in %s", ch, s);
   
   return 0;
}

Output

Output of this program should be −

a appears 3 times in 'TajMahal'

4.Program to count vowels occurrent in C

#include <stdio.h>

int main() {
   char s[] = "TajMahal";     // String Given
   int i = 0;
   int vowels = 0;            // Vowels counter
   int consonants = 0;        // Consonants counter

   while(s[i++] != '\0') {
      if(s[i] == 'a' || s[i] == 'e' || s[i] == 'i' || s[i] == 'o' || s[i] == 'u' )
         vowels++;
      else
         consonants++;
   }

   printf("'%s' contains %d vowels and %d consonants.", s, vowels, consonants);

   return 0;
}

Output

Output of this program should be −

'TajMahal' contains 3 vowels and 5 consonants.

5.Program to sort string characters in C

#include <stdio.h>
#include <string.h>

int main (void) {
   char string[] = "simplyeasylearning";
   char temp;

   int i, j;
   int n = strlen(string);

   printf("String before sorting - %s \n", string);

   for (i = 0; i < n-1; i++) {
      for (j = i+1; j < n; j++) {
         if (string[i] > string[j]) {
            temp = string[i];
            string[i] = string[j];
            string[j] = temp;
         }
      }
   }
   
   printf("String after sorting  - %s \n", string);
   return 0;
}

Output

Output of this program should be −

String before sorting - simplyeasylearning
String after sorting  - aaeegiillmnnprssyy

Multi-string Programs

These programs has more than one string variables. These should give you an insight of how to work with multiple string variables in C programming language −

1.Program to copy string in C

#include <stdio.h>

int main() {
   char s1[] = "TajMahal";       // String Given
   char s2[8];                   // Variable to hold value

   int length = 0;

   while(s1[length] != '\0') {
      s2[length] = s1[length];
      length++;
   }

   s2[length] = '\0';           // Terminate the string

   printf("Value in s1 = %s \n", s1);
   printf("Value in s2 = %s \n", s2);

   return 0;
}

Output

Output of this program should be −

Value in s1 = TajMahal
Value in s2 = TajMahal

2.Program to reverse string in C

#include <stdio.h>

int main() {
   char s1[] = "TajMahal";    // String Given
   char s2[8];                // Variable to store reverse string

   int length = 0;
   int loop = 0;

   while(s1[length] != '\0') {
      length++;
   }

   printf("\nPrinting in reverse - ");
   for(loop = --length; loop>=0; loop--)
      printf("%c", s1[loop]);

   loop = 0;
   printf("\nStoring in reverse  - ");

   while(length >= 0) {
      s2[length] = s1[loop];
      length--;
      loop++;
   }

   s1[loop] = '\0';           // Terminates the string

   printf("%s\n", s2);

   return 0;
}

Output

Output of this program should be −

Printing in reverse - lahaMjaT
Storing in reverse  - lahaMjaT

3.Program to search strings in C

#include <stdio.h>
#include <string.h>

int main() {
   char s1[] = "Beauty is in the eye of the beholder";
   char s2[] = "the";

   int n = 0;
   int m = 0;
   int times = 0;
   int len = strlen(s2);      // contains the length of search string

   while(s1[n] != '\0') {

      if(s1[n] == s2[m]) {     // if first character of search string matches

         // keep on searching

         while(s1[n] == s2[m]  && s1[n] !='\0') {
            n++;
            m++;
         }

         // if we sequence of characters matching with the length of searched string
         if(m == len && (s1[n] == ' ' || s1[n] == '\0')) {

            // BINGO!! we find our search string.
            times++;
         }
      } else {            // if first character of search string DOES NOT match
         while(s1[n] != ' ') {        // Skip to next word
            n++;
            if(s1[n] == '\0')
            break;
         }
      }
  
      n++;
      m=0;  // reset the counter to start from first character of the search string.
   }

   if(times > 0) {
      printf("'%s' appears %d time(s)\n", s2, times);
   } else {
      printf("'%s' does not appear in the sentence.\n", s2);
   }

   return 0;
}

Output

Output of this program should be −

'the' appears 2 time(s)

4.Program to swap strings in C

#include <stdio.h>

int main() {
   char s1[] = "TajMahal";     
   char s2[] = "Dazzling";     
   char ch;

   int index = 0;

   //Character by Character approach

   printf("Before Swapping - \n");
   printf("Value of s1 - %s \n", s1);
   printf("Value of s2 - %s \n", s2);

   while(s1[index] != '\0') {
      ch = s1[index];
      s1[index] = s2[index];
      s2[index] = ch;
      index++;
   }

   printf("After Swapping - \n");
   printf("Value of s1 - %s \n", s1);
   printf("Value of s2 - %s \n", s2);

   return 0;
}

Output

Output of this program should be −

Before Swapping -
Value of s1 - TajMahal
Value of s2 - Dazzling
After Swapping -
Value of s1 - Dazzling

5.Program to compare two strings in C

#include <stdio.h>

int main() {
   char s1[] = "advise";     
   char s2[] = "advice";
    
   int n = 0;
   unsigned short flag = 1; 
    
   while (s1[n] != '\0') {
      if(s1[n] != s2[n]) {
         flag = 0;
         break;
      }
      n++;
   }
    
   if(flag == 1) {
      printf("%s and %s are identical\n", s1, s2);
   } else {
      printf("%s and %s are NOT identical\n", s1, s2);
   }

   return 0;
}

Output

Output of this program should be −

advise and advice are NOT identical

6.Program to concatenate two strings in C

#include <stdio.h>
#include <string.h>

int main() {
   char s1[10] = "Taj";
   char s2[] = "Mahal";

   int i, j, n1, n2;

   n1 = strlen(s1);
   n2 = strlen(s2);

   j = 0;
   for(i = n1; i< n1+n2; i++ ) {
      s1[i] = s2[j];
      j++;
   }

   s1[i] = '\0';

   printf("%s", s1);

   return 0;
}

Output

Output of this program should be −

TajMahal

7.String Anagram program in in C

#include <stdio.h>
#include <string.h>

int main (void) {
   char s1[] = "recitals";
   char s2[] = "articles";

   char temp;

   int i, j;
   int n  = strlen(s1);
   int n1 = strlen(s2);

   // If both strings are of different length, then they are not anagrams

   if( n != n1) {    
      printf("%s and %s are not anagrams! \n", s1, s2);
      return 0;
   }
   
   // lets sort both strings first −

   for (i = 0; i < n-1; i++) {
      for (j = i+1; j < n; j++) {
         if (s1[i] > s1[j]) {
            temp  = s1[i];
            s1[i] = s1[j];
            s1[j] = temp;
         }
         if (s2[i] > s2[j]) {
            temp  = s2[i];
            s2[i] = s2[j];
            s2[j] = temp;
         }
      }
   }

   // Compare both strings character by character

   for(i = 0; i<n; i++) {
      if(s1[i] != s2[i]) {    
         printf("Strings are not anagrams! \n", s1, s2);
         return 0;
      }
   }

   printf("Strings are anagrams! \n");
   return 0;
}

Output

Output of this program should be −

Strings are anagrams!

Long String Programs

A sentence or a line can be considered as a long string. The following programs deals with the same concept −

1.C Program to reverse words in a line

• 
  

#include <stdio.h>
#include <string.h>

int string_length(char s[]) {
   int i = 0;

   while(s[i]!='\0')
      i++;

   return i; 
}

void string_reverse(char st[]) {
   int i,j,len;
   char ch;

   j = len = string_length(st) - 1;
   i = 0;

   while(i < j) {
      ch = st[j];
      st[j] = st[i];
      st[i] = ch;
      i++;
      j--;
   }
}

int main (void) {
   char line[] = "Taj Mahal is one of the seven wonders of the world";
   char reverse[100]="",temp[50];
   int i,j,n;

   n = string_length(line);

   for(i = 0; i < n; i++) {

      for(j = 0; i < n && line[i]!=' '; ++i,++j) {
         temp[j] = line[i];
      }
      
      temp[j] = '\0';

      string_reverse(temp);

      strcat(reverse, temp);
      strcat(reverse, " ");
   }
   
   printf("Original - %s\n", line);
   printf("Reversed - %s\n",reverse);
   
   return 0;
}

Output

Output of this program should be −

Original - Taj Mahal is one of the seven wonders of the world
Reversed - jaT lahaM si eno fo eht neves srednow fo eht dlrow

2.C Program to reverse a line

#include <stdio.h>
#include <string.h>

int string_length(char s[]) {
   int i = 0;

   while(s[i]!='\0')
      i++;

   return i; 
}

void string_reverse(char st[]) {
   int i,j,len;
   char ch;

   j = len = string_length(st) - 1;
   i = 0;

   while(i < j) {
      ch = st[j];
      st[j] = st[i];
      st[i] = ch;
      i++;
      j--;
   }
}

int main (void) {
   char line[] = "Taj Mahal is one of the seven wonders of the world";
   char reverse[100] = "", temp[50];
   int i, j, n;

   n = string_length(line);

   for(i = n-1; i >= 0; --i) {

      for(j = 0; i >= 0 && line[i] != ' '; --i,++j)
         temp[j] = line[i];

      temp[j] = '\0';

      string_reverse(temp);
      
      strcat(reverse,temp);
      strcat(reverse," ");
   }

   printf("Original - %s\n", line);
   printf("Reversed - %s\n",reverse);

   return 0;
}

Output

Output of this program should be −

Original - Taj Mahal is one of the seven wonders of the world
Reversed - world the of wonders seven the of one is Mahal Taj

• Functions

A function is a group of statements that together perform a task. Every C program has at least one function, which is main(), and all the most trivial programs can define additional functions.

You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division is such that each function performs a specific task.

A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.

The C standard library provides numerous built-in functions that your program can call. For example, strcat() to concatenate two strings, memcpy() to copy one memory location to another location, and many more functions.

A function can also be referred as a method or a sub-routine or a procedure, etc.

Defining a Function

The general form of a function definition in C programming language is as follows −

return_type function_name( parameter list ) {
   body of the function
}

A function definition in C programming consists of a function header and a function body. Here are all the parts of a function −

• Return Type − A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return_type is the keyword void.
• Function Name − This is the actual name of the function. The function name and the parameter list together constitute the function signature.
• Parameters − A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.
• Function Body − The function body contains a collection of statements that define what the function does.

Example

Given below is the source code for a function called max(). This function takes two parameters num1 and num2 and returns the maximum value between the two −

/* function returning the max between two numbers */
int max(int num1, int num2) {

   /* local variable declaration */
   int result;
 
   if (num1 > num2)
      result = num1;
   else
      result = num2;
 
   return result; 
}

Function Declarations

A function declaration tells the compiler about a function name and how to call the function. The actual body of the function can be defined separately.

A function declaration has the following parts −

return_type function_name( parameter list );

For the above defined function max(), the function declaration is as follows −

int max(int num1, int num2);

Parameter names are not important in function declaration only their type is required, so the following is also a valid declaration −

int max(int, int);

Function declaration is required when you define a function in one source file and you call that function in another file. In such case, you should declare the function at the top of the file calling the function.

Calling a Function

While creating a C function, you give a definition of what the function has to do. To use a function, you will have to call that function to perform the defined task.

When a program calls a function, the program control is transferred to the called function. A called function performs a defined task and when its return statement is executed or when its function-ending closing brace is reached, it returns the program control back to the main program.

To call a function, you simply need to pass the required parameters along with the function name, and if the function returns a value, then you can store the returned value. For example −

#include <stdio.h>
 
/* function declaration */
int max(int num1, int num2);
 
int main () {

   /* local variable definition */
   int a = 100;
   int b = 200;
   int ret;
 
   /* calling a function to get max value */
   ret = max(a, b);
 
   printf( "Max value is : %d\n", ret );
 
   return 0;
}
 
/* function returning the max between two numbers */
int max(int num1, int num2) {

   /* local variable declaration */
   int result;
 
   if (num1 > num2)
      result = num1;
   else
      result = num2;
 
   return result; 
}

We have kept max() along with main() and compiled the source code. While running the final executable, it would produce the following result −

Max value is : 200

Function Arguments

If a function is to use arguments, it must declare variables that accept the values of the arguments. These variables are called the formal parameters of the function.

Formal parameters behave like other local variables inside the function and are created upon entry into the function and destroyed upon exit.

While calling a function, there are two ways in which arguments can be passed to a function −

Sr.No.	Call Type & Description
1	Call by value This method copies the actual value of an argument into the formal parameter of the function. In this case, changes made to the parameter inside the function have no effect on the argument.
2	Call by reference This method copies the address of an argument into the formal parameter. Inside the function, the address is used to access the actual argument used in the call. This means that changes made to the parameter affect the argument.

By default, C uses call by value to pass arguments. In general, it means the code within a function cannot alter the arguments used to call the function.

Advanced

• Pointers
• Structures
• Function arguments by reference
• Dynamic allocation
• Arrays and Pointers
• Recursion
• Linked lists
• Binary trees

note:-Advanced topic will be updated soon