Chapter 4 - Programming In C : Computer Sci NEB Class 12

Chapter 1: Review of C Programming Concepts

Basic Input/Output Functions

Examples of basic programs demonstrating input and output.

WAP to add any two numbers 3 & 5

/*WAP to add any two numbers 3 & 5 */
#include<stdio.h>
#include<conio.h>
void main()
{
    int a,b,sum;
    a=3;
    b=5;
    sum=a+b;
    printf("The sum is %d",sum);
    getch();
}

WAP to input any two numbers and add them

/* WAP to input any two numbers and add them */
#include<stdio.h>
#include<conio.h>
void main()
{
    int a,b,sum;
    printf("Enter first number: ");
    scanf("%d",&a);
    printf("Enter second number: ");
    scanf("%d",&b);
    sum=a+b;
    printf("The sum is %d",sum);
    getch();
}

WAP to find simple interest

/*WAP to find simple interest*/
#include<stdio.h>
#include<conio.h>
void main()
{
    float p,t,r,si;
    printf("Enter the value of principle, rate & time: ");
    scanf("%f%f%f",&p,&r,&t);
    si=(p*r*t)/100;
    printf("\n Simple Interest (SI) = %f",si);
    getch();
}

WAP to find the area & perimeter of circle

/* WAP to find the area & perimeter of circle*/
#include<stdio.h>
#include<conio.h>
#define pi 3.14
void main()
{
    float r;
    printf("Enter the radius of the circle: ");
    scanf("%f",&r);
    printf("The area of the circle is %f ",pi*r*r);
    printf("\n and the perimeter is %f.",2*pi*r);
    getch();
}

WAP to find square root of any number

/* WAP to find square root of any number */
#include<stdio.h>
#include<conio.h>
#include<math.h>
void main()
{
    int a;
    float r;
    printf("Enter any number: ");
    scanf("%d",&a);
    r=sqrt(a);
    printf("The square root of %d is %f.",a,r);
    getch();
}

WAP to convert hours into minute & seconds

/* WAP to convert hours into minute & Seconds*/
#include<stdio.h>
#include<conio.h>
void main()
{
    int h;
    printf("Enter the time in hours: ");
    scanf("%d",&h);
    printf("%d Hours = %d Minutes",h,h*60);
    printf("\n %d Hours = %d Seconds",h,h*60*60);
    getch();
}

WAP to add the first & last digit of any 4 digit number

/* WAP to add the first & last digit of any 4 digit number */
#include<stdio.h>
#include<conio.h>
void main()
{
    int n,a,b,sum=0;
    printf("Enter a four digit number: ");
    scanf("%d",&n);
    a=n/1000;   /* to seperate first digit*/
    b=n%10;     /* to seperate the last digit */
    sum=a+b;
    printf("The sum of first & last digit is %d",sum);
    getch();
}

Control Structures

WAP to check if a given number is odd or even

/* WAP to check the given number is odd or even */
#include<stdio.h>
#include<conio.h>
void main()
{
    int n;
    printf("Enter any number: ");
    scanf("%d",&n);
    if(n%2==0)
    {
        printf("\n The number is even");
    }
    else
    {
        printf("\n The number is odd");
    }
    getch();
}

WAP to find the factorial of a given number

/*WAP to find factorial of a given number*/
#include<stdio.h>
#include<conio.h>
void main()
{
    int n,i,fact=1;
    printf("Enter a number to find factorial: ");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        fact=fact*i;
    }
    printf("\n The factorial is %d",fact);
    getch();
}

WAP to find reverse of a given number & check if it is a palindrome

/*WAP to find reverse of a given number & check if the number is
palindrome or not*/
#include<stdio.h>
#include<conio.h>
void main()
{
    int n,temp,rev=0,pal;
    printf("Enter any number: ");
    scanf("%d",&n);
    pal=n;
    while(n!=0)
    {
        temp=n%10;
        rev=rev*10+temp;
        n=n/10;
    }
    printf("\n Reverse of the given number is %d",rev);
    if(rev==pal)
    {
        printf("\n The number is palindrome");
    }
    else
    {
        printf("\n The number is not palindrome");
    }
    getch();
}

WAP to find fibonacci series up to 'n' terms

/*WAP to find fibonacci series up to 'n' terms*/
#include<stdio.h>
#include<conio.h>
void main()
{
    int a=0,b=1,c,i,n;
    printf("Enter a number for fibonacci series: ");
    scanf("%d",&n);
    printf("%d \t %d",a,b);
    for(i=3;i<=n;i++)
    {
        c=a+b;
        printf("\t%d",c);
        a=b; b=c;
    }
    getch();
}

Chapter 2: Arrays and Strings

Array

An array is a special variable that can store more than one similar type of value under the same name with different index numbers.

Syntax:

datatype arrayName[array-size];
// e.g. -> int a[10];

Q. WAP to ask for 5 numbers and display the same numbers.

#include<stdio.h>
#include<conio.h>
void main()
{
    clrscr();
    int a[5], i;
    for(i=0; i<5; i++)
    {
        printf("enter %d number\n", i+1);
        scanf("%d", &a[i]);
    }
    printf("The numbers you have entered are \n");
    for(i=0; i<5; i++)
    {
        printf("%d ", a[i]);
    }
    getch();
}

Output:

Enter 1 number
5
Enter 2 number
3
Enter 3 number
4
Enter 4 number
2
Enter 5 number
1
The number you have entered are 5 3 4 2 1

Q. WAP to ask for computer marks of 10 students & display the mark which is increased by 2.

#include <stdio.h>
#include <conio.h>
void main()
{
    clrscr();
    int mark[10], i;
    for (i=0; i<10; i++)
    {
        printf("enter mark of %d student \n", i+1);
        scanf("%d", &mark[i]);
    }
    printf("The marks after adding 2 marks on previous mark are\n");
    for (i=0; i<10; i++)
    {
        printf("%d ", mark[i]+2);
    }
    getch();
}

Q. WAP to ask for 2 matrices of order 2x2 and display the matrix addition.

#include <stdio.h>
#include <conio.h>
void main()
{
    clrscr();
    int A[2][2], B[2][2], C[2][2], i, j;
    
    printf("enter matrix A\n");
    for(i=0; i<2; i++)
    {
        for(j=0; j<2; j++)
        {
            scanf("%d", &A[i][j]);
        }
    }

    printf("enter matrix B\n");
    for(i=0; i<2; i++)
    {
        for(j=0; j<2; j++)
        {
            scanf("%d", &B[i][j]);
        }
    }

    for(i=0; i<2; i++)
    {
        for(j=0; j<2; j++)
        {
            C[i][j] = A[i][j] + B[i][j];
        }
    }

    printf("The addition is \n");
    for(i=0; i<2; i++)
    {
        for(j=0; j<2; j++)
        {
            printf("%d ", C[i][j]);
        }
        printf("\n");
    }
    getch();
}

String Functions

String function is a library function which is used to find the length of a given string, reverse the string, copy the string, change into upper case or lower case, compare the two strings, etc.

There are 7 main string functions. They are:

1. strlen()
2. strrev()
3. strcat()
4. strupr()
5. strlwr()
6. strcmp()
7. strcpy()

1. strlen()

This string function is used to find the length of string. Its keyword is strlen().

For example:

#include<stdio.h>
#include <conio.h>
#include<string.h>
void main()
{
    clrscr();
    int x;
    char word[50];
    printf("enter a word ");
    scanf("%s", word);
    x = strlen(word);
    printf("The length of word is %d ", x);
    getch();
}

Output:

enter a word prapti
The length of word is 6 

2. strrev()

This string function is used to reverse the given string.

For example:

#include<stdio.h>
#include<conio.h>
#include <string.h>
void main()
{
    clrscr();
    char word[25];
    printf("enter a word\n");
    scanf("%s", word);
    strrev(word);
    printf("The reversed word is %s", word);
    getch();
}

Output:

Enter a word
prapti
The reversed word is itparp

3. strcat()

This string function is used to join two strings together.

For example:

#include <stdio.h>
#include<conio.h>
#include <string.h>
void main()
{
    clrscr();
    char word1[25], word2[25];
    printf("enter two words\n");
    scanf("%s %s", word1, word2);
    strcat(word1, word2);
    printf("The combined word is %s", word1);
    getch();
}

Output:

Enter two words
gita sita
The combined word is gitasita

4. strupr()

The string function is used to convert lower case into upper case letter.

For example:

#include<stdio.h>
#include<conio.h>
#include <string.h>
void main()
{
    clrscr();
    char word[25];
    printf("enter a word\n");
    scanf("%s", word);
    strupr(word);
    printf("The upper case letter is %s", word);
    getch();
}

Output:

Enter a word
prapti
The upper case letter is PRAPTI

5. strlwr()

The string function is used to convert upper case into lower case letter.

For example:

#include<stdio.h>
#include<conio.h>
#include <string.h>
void main()
{
    clrscr();
    char word[25];
    printf("enter a word\n");
    scanf("%s", word);
    strlwr(word);
    printf("The lower case letter is %s", word);
    getch();
}

Output:

Enter a word
PRAPTI
The lower case letter is prapti

6. strcmp()

This string function is used to compare two strings.

For example:

#include<stdio.h>
#include <conio.h>
#include <string.h>
void main()
{
    clrscr();
    char word1[25], word2[25];
    printf("enter two words\n");
    scanf("%s %s", word1, word2);
    if (strcmp(word1, word2) == 0)
    {
        printf("Both strings are same");
    }
    else
    {
        printf("Both strings are not same");
    }
    getch();
}

Output:

enter two words
prapti prapti
Both strings are same

7. strcpy()

This string function is used to copy a string from one string variable to another variable.

For example:

#include<stdio.h>
#include<conio.h>
#include <string.h>
void main()
{
    clrscr();
    char word1[25], word2[25];
    printf("enter a word\n");
    scanf("%s", word2);
    strcpy(word1, word2);
    printf("The copied word is %s", word1);
    getch();
}

Output:

enter a word
prapti
The copied word is prapti

Q. WAP to check whether the given word is a palindrome or not.

#include <stdio.h>
#include<conio.h>
#include <string.h>
void main()
{
    clrscr();
    char word1[25], word2[25];
    printf("enter a word \n");
    scanf("%s", word1);
    strcpy(word2, word1);
    strrev(word1);
    if(strcmp(word1, word2) == 0)
    {
        printf("palindrome");
    }
    else
    {
        printf("Not palindrome");
    }
    getch();
}

Output:

Enter a word
prapti
Not palindrome

Chapter 3: Functions

Concept of function

A function is a self-contained program segment or the block of statements that perform some specific, well-defined task. Every C program comprises one or more such functions. The execution of any program always begins by executing the instructions in the main() function.

Types of Function

1. Library / Built-in Functions
2. User-defined functions

a. Library / Built-in functions

The library function is defined by the developer of the C-language. It cannot be changed or altered. We can use a library function by simply adding a header file.

For example:

1. printf(), scanf() are defined in header file stdio.h
2. getch(), clrscr() are defined in header file conio.h
3. strlen(), strupr() are defined in header file string.h
4. pow(), sqrt() are defined in header file math.h

b. User-defined Function

This type of function is defined by the user or programmer as per their need. We can use a user-defined function by simply declaring a function.

For example: aor(), vol(), sum(), factorial(), etc.

Components of function

1. Function prototype (Function declaration)
2. Function call
3. Function Definition
4. return and void statements of a function.

Actual argument and Formal Argument

Arguments defined inside the function are called Formal arguments. The argument from which the arguments have been passed to a function is known as actual arguments.

Categories of user-defined function

1. Function without any arguments and return values
2. Function with arguments but no return values
3. Function with arguments and with return values
4. Function without any arguments but with return values

1. Function without any arguments and return values

Here, we simply call a function without passing arguments and the called function doesn't have to return any values to the calling function. If we do not want to return a value, we must use the return type void and miss out on the return statement.

For example: //WAP to find the area of a rectangle using function.

#include<stdio.h>
#include<conio.h>
void AOR();
void main()
{
    clrscr();
    AOR();
    getch();
}
void AOR()
{
    int l, b, area;
    printf("write the length\n");
    scanf("%d", &l);
    printf("write the breadth\n");
    scanf("%d", &b);
    area = l*b;
    printf("The area of rectangle is %d", area);
}

Output:

write the length
5
write the breadth
10
The area of rectangle is 50

2. Function with arguments but no return values

This type of function has one-way communication. Here, an argument is passed from the calling function to the called function, but there is no need for a return statement in the called function.

For example: // WAP to find the area of a rectangle using function.

#include<stdio.h>
#include<conio.h>
void AOR(int, int);
void main()
{
    clrscr();
    int l, b;
    printf("enter length & breadth\n");
    scanf("%d %d", &l, &b);
    AOR(l, b);
    getch();
}
void AOR(int l, int b)
{
    int area;
    area = l*b;
    printf("The area of rectangle is %d", area);
}

3. Function with arguments and with return values

This type of function has two-way communication. Here, an argument is passed from the calling function to the called function, and there will also be a returning statement in the called function.

For example:

#include<stdio.h>
#include<conio.h>
int AOR(int, int);
void main()
{
    clrscr();
    int l, b, x;
    printf("enter length and breadth\n");
    scanf("%d %d", &l, &b);
    x = AOR(l, b);
    printf("The area of rectangle is %d", x);
    getch();
}
int AOR(int l, int b)
{
    int area;
    area = l*b;
    return area;
}

4. Function without any arguments but with return values

This type of function also has one-way communication. Here, an argument is not passed from the calling function to the called function, but there is a need for a return statement in the called function.

For example:

#include <stdio.h>
#include <conio.h>
int AOR();
void main()
{
    clrscr();
    int x;
    x = AOR();
    printf("The area of rectangle is %d", x);
    getch();
}
int AOR()
{
    int l, b, area;
    printf("enter length and breadth\n");
    scanf("%d %d", &l, &b);
    area = l*b;
    return area;
}

Concept of Recursion

A recursive function is one, which calls itself. A recursive function contains the following features:

1. The function should call itself.
2. The function should have a stopping condition.

The concept of using the recursive function to repeat the execution of a statement many times is known as recursion.

For example: WAP to find the factorial of a given number using recursive function.

#include<stdio.h>
#include<conio.h>
int factorial(int);
void main()
{
    clrscr();
    int n, fact;
    printf("enter a number\n");
    scanf("%d", &n);
    fact = factorial(n);
    printf("The factorial of %d is %d", n, fact);
    getch();
}
int factorial(int n)
{
    if (n == 0 || n == 1)
    {
        return 1;
    }
    else
    {
        return (n * factorial(n-1));
    }
}

Output:

enter a number
2
The factorial of 2 is 2

Chapter 4: Structures and Unions

Structure

A structure is the collection of one or more variables of different datatypes (e.g: int, float, char), grouped together under a single name. We can have an array of structure. The keyword struct is used to declare a Structure.

For example: WAP to store five employees records (EID, name, post and department) and display them using structure.

#include<stdio.h>
#include <conio.h>
struct employee
{
    int eid;
    char name[50];
    char post[50];
    char dep[50];
} emp[5];

void main()
{
    clrscr();
    int i;
    for (i=0; i<5; i++)
    {
        printf("Enter eid, name, post and department of %d employee\n", i+1);
        scanf("%d %s %s %s", &emp[i].eid, emp[i].name, emp[i].post, emp[i].dep);
    }
    
    clrscr();
    printf("The records of employees are listed below\n");
    printf("EID\t\tName\t\tpost\t\tDepartment\n");
    for(i=0; i<5; i++)
    {
        printf("%d\t\t%s\t\t%s\t\t%s\n", emp[i].eid, emp[i].name, emp[i].post, emp[i].dep);
    }
    getch();
}

WAP to store 3 students records (grade, rollno, name and faculty) and display them using structure.

#include<stdio.h>
#include<conio.h>
struct students
{
    int grade;
    int rollno;
    char name[50];
    char faculty[50];
} std[3];

void main()
{
    clrscr();
    int i;
    for(i=0; i<3; i++)
    {
        printf("Enter grade, rollno, name and Faculty of %d Student\n", i+1);
        scanf("%d %d %s %s", &std[i].grade, &std[i].rollno, std[i].name, std[i].faculty);
    }
    
    clrscr();
    printf("The records of students are listed below\n");
    printf("Grade\t\tRollno\t\tName\t\tFaculty\n");
    for(i=0; i<3; i++)
    {
        printf("%d\t\t%d\t\t%s\t\t%s\n", std[i].grade, std[i].rollno, std[i].name, std[i].faculty);
    }
    getch();
}

Chapter 5: Pointers

What is a pointer? Why should we use a pointer?

A pointer is a variable that holds the memory location of another variable rather than the actual value. We use a pointer variable because it stores an address or memory location and points to whatever that memory location contains.

Advantages of Pointers:

1. Pointers enable us to access a variable that is defined outside the function.
2. Pointers reduce the length and complexity of the program and increase execution speed.
3. Pointers are more efficient in handling data tables.
4. Pointers are also more efficient in handling the data array.
5. Pointers are used to create complex data structures such as linked lists, trees.

What are the two operators used in pointers?

The two operators used in pointers are as follows:

• a. Address of operator (&) ampersand: Address of operator is the ampersand, i.e., &. It is a unary operator i.e. applied to a variable to assign its memory address.
• b. Indirection or dereference operator (*) Asterisk: It is denoted by "*" sign. This unary operator accesses the values residing at a memory address.

How do you declare a pointer?

Pointer declaration:

data-type *pointer-variable;
i.e. int *p;

Pointer Examples

Find the output of the following program.

// Program 1
int main()
{
    int b = 25;
    // memory location of b is 1234
    int *p;
    p = &b;
    printf("%d %d", &b, p);
    return 0;
}
// Output: 1234 1234

// Program 2
int main()
{
    int a = 5;
    int *q;
    q = &a;
    printf("%d %d", a, *q);
    return 0;
}
// Output: 5 5

// Program 3
int main()
{
    int x = 5;
    // memory address of x is 2000
    int *p;
    p = &x;
    printf("%d %d", p, *p);
    return 0;
}
// Output: 2000 5

// Program 4
int main()
{
    int x = 5, y = 10;
    int *p = &x, *q = &y;
    *q = 5;
    printf("%d", *p + *q);
    return 0;
}
// Output: 10

Chapter 6: Working with Files

File Handling

Why do you need a file?

As we know, while the program is processing, the content of variables are stored in RAM. But the problem is if such values of a variable are needed in the future, then this causes the problem because the value of the variable is only within the program being processed. After a program is over, the content of the RAM is erased. To overcome this problem we can use a data file to save the content into it, so that we can retrieve content from the data file whenever we want.

File Handling Functions and Modes

Operators/Functions that We Use for File Handling in C

Describe file handling modes in C

These are different ways a file is to be opened. The different file opening modes are:

File Handling Examples

Q. WAP to read name & salary of 10 employees and store all the data in a file named "emp.txt" and also display all the records from the file to the output screen.

#include<stdio.h>
#include<conio.h>
void main()
{
    int i, sal;
    char name[50];
    FILE *fp;

    fp = fopen("emp.txt", "w");
    for (i=0; i<10; i++)
    {
        printf("Enter name & salary of %d employee\n", i+1);
        scanf("%s %d", name, &sal);
        fprintf(fp, "%s\t%d\n", name, sal);
    }
    fclose(fp);

    printf("The records of employees are\n");
    printf("Name\t\tSalary\n");
    fp = fopen("emp.txt", "r");
    for(i=0; i<10; i++)
    {
        fscanf(fp, "%s %d", name, &sal);
        printf("%s\t\t%d\n", name, sal);
    }
    fclose(fp);
    getch();
}

Write a program to create and write data into file.

#include <stdio.h>
#include <conio.h>
#include <string.h>
void main()
{
    clrscr();
    int rollno;
    char name[50], address[50], choice[2];
    FILE *fp;
    fp = fopen("std.txt", "w");
    do
    {
        printf("Enter rollno, name and address of a student\n");
        scanf("%d %s %s", &rollno, name, address);
        fprintf(fp, "%d\t%s\t%s\n", rollno, name, address);
        printf("Do you want to enter more data (y/n)\n");
        scanf("%s", choice);
        strupr(choice);
    } while (strcmp(choice, "Y") == 0);
    
    fclose(fp);
    printf("All data are saved successfully");
    getch();
}