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Thread: Important C Programs With Solutions

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    Important C Programs With Solutions

    Programs


    1. Write a program to find factorial of the given number....
    2. Write a program to check whether the given number is even or odd.
    3. Write a program to swap two numbers using a temporary variable.
    4. Write a program to swap two numbers without using a temporary variable.
    5. Write a program to swap two numbers using bitwise operators.
    6. Write a program to find the greatest of three numbers.
    7. Write a program to find the greatest among ten numbers.
    8. Write a program to check whether the given number is a prime.
    9. Write a program to check whether the given number is a palindromic number.
    10.Write a program to check whether the given string is a palindrome.
    11.Write a program to generate the Fibonacci series.
    12.Write a program to print "Hello World" without using semicolon anywhere in the code.
    13.Write a program to print a semicolon without using a semicolon anywhere in the code.
    14.Write a program to compare two strings without using strcmp() function.
    15.Write a program to concatenate two strings without using strcat() function.
    16.Write a program to delete a specified line from a text file.
    17.Write a program to replace a specified line in a text file.
    18.Write a program to find the number of lines in a text file..
    19.Write a C program which asks the user for a number between 1 to 9 and shows the number. If the user
    inputs a number out of the specified range, the program should show an error and prompt the user for a
    valid input.
    20.Write a program to display the multiplication table of a given number..

    The above 20 codes are collected and posted here by : Shrihari,,Since there are many codes asked in interviews,and those are a bit complex than them,i tried to solved them in my level,and posted here..so,,
    Some of my codes that i solved(except WORLD MAP),that i think are important,,i wanna share with you all..I tried my best to make them good,but If there is any bug,let me know..
    "Amit Aru"

    21.WAP to check a string is Caliondrome or not. //Maventic question.
    22.WAP to print DONE,without using any loop. // asked to my frnd in any company.
    23.WAP to print DONE,without using any loop and any conditonal clause or operators. // asked to me as a cross question of 22th question by the person i asked 22th ques.
    24. WAP to find out the longest word in a string.
    25.Prog of WORLD MAP. // this code was written by someone,i forgot his name,he won award for this code as short and best c code. JUST FOR FUN //
    26.WAP to print the triangle of letters in increasing order of lines..
    27.WAP to print 'xay' in place of every 'a' in a string.//DOC Update on 24-jan-12.
    28.Count the Total Number of 7 comming between 1 to 100.
    /* I made this code in a way that u can give Upper limit i.e. 100,Lower limit i.e. 1 and the specific number u wants to count in between i.e. 7 */ // asked by: Vishwa Pratap Rana..
    29. Code for duplicate's removal,by Amit Aru.. // Similar question was asked in Maventic 2nd round to me,,
    30. WAP to find out if a given number is a power series of 2 or not,without any loop and without using % modulo operator..// asked by someone on BJS..

    TO BE CONTINUED...!!!



    ANSWERS
    1. Write a program to find factorial of the given number.

    Recursion: A function is called 'recursive' if a statement within the body of a function calls the same function. It
    is also called 'circular definition'. Recursion is thus a process of defining something in terms of itself.
    Program: To calculate the factorial value using recursion.
    #include <stdio.h>
    int fact(int n);
    int main() {
    int x, i;
    printf("Enter a value for x: \n");
    scanf("%d", &x);
    i = fact(x);
    printf("\nFactorial of %d is %d", x, i);
    return 0;
    } int fact(int n) {
    /* n=0 indicates a terminating condition */
    if (n <= 0) {
    return (1);
    } else {
    /* function calling itself */
    return (n * fact(n - 1));
    /*n*fact(n-1) is a recursive expression */
    }
    }
    Output:
    Enter a value for x:
    4
    Factorial of 4 is 24
    Explanation:
    fact(n) = n * fact(n-1)
    If n=4
    fact(4) = 4 * fact(3) there is a call to fact(3)
    fact(3) = 3 * fact(2)
    fact(2) = 2 * fact(1)
    fact(1) = 1 * fact(0)
    fact(0) = 1
    fact(1) = 1 * 1 = 1
    fact(2) = 2 * 1 = 2
    fact(3) = 3 * 2 = 6
    Thus fact(4) = 4 * 6 = 24
    Terminating condition(n <= 0 here;) is a must for a recursive program. Otherwise the program enters into an
    infinite loop.


    2. Write a program to check whether the given number is even or odd.
    Program:
    #include <stdio.h>
    int main() {
    int a;
    printf("Enter a: \n");
    scanf("%d", &a);
    /* logic */
    if (a % 2 == 0) {
    printf("The given number is EVEN\n");
    }
    else {
    printf("The given number is ODD\n");
    }
    return 0;
    }
    Output:
    Enter a: 2
    The given number is EVEN
    Explanation with examples:
    Example 1: If entered number is an even number
    Let value of 'a' entered is 4
    if(a%2==0) then a is an even number, else odd.
    i.e. if(4%2==0) then 4 is an even number, else odd.
    To check whether 4 is even or odd, we need to calculate (4%2).
    /* % (modulus) implies remainder value. */
    /* Therefore if the remainder obtained when 4 is divided by 2 is 0, then 4 is even. */
    4%2==0 is true
    Thus 4 is an even number.
    Example 2: If entered number is an odd number.
    Let value of 'a' entered is 7
    if(a%2==0) then a is an even number, else odd.
    i.e. if(7%2==0) then 4 is an even number, else odd.
    To check whether 7 is even or odd, we need to calculate (7%2).
    7%2==0 is false /* 7%2==1 condition fails and else part is executed */
    Thus 7 is an odd number.


    3. Write a program to swap two numbers using a temporary variable.
    Swapping interchanges the values of two given variables.
    Logic:
    step1: temp=x;
    step2: x=y;
    step3: y=temp;
    Example:
    if x=5 and y=8, consider a temporary variable temp.
    step1: temp=x=5;
    step2: x=y=8;
    step3: y=temp=5;
    Thus the values of the variables x and y are interchanged.
    Program:
    #include <stdio.h>
    int main() {
    int a, b, temp;
    printf("Enter the value of a and b: \n");
    scanf("%d %d", &a, &b);
    printf("Before swapping a=%d, b=%d \n", a, b);
    /*Swapping logic */
    temp = a;
    a = b;
    b = temp;
    printf("After swapping a=%d, b=%d", a, b);
    return 0;
    }
    Output:
    Enter the values of a and b: 2 3
    Before swapping a=2, b=3
    After swapping a=3, b=2
    4. Write a program to swap two numbers without using a temporary variable.
    Swapping interchanges the values of two given variables.
    Logic:
    step1: x=x+y;
    step2: y=x-y;
    step3: x=x-y;
    Example:
    if x=7 and y=4
    step1: x=7+4=11;
    step2: y=11-4=7;
    step3: x=11-7=4;
    Thus the values of the variables x and y are interchanged.
    Program:
    #include <stdio.h>
    int main() {
    int a, b;
    printf("Enter values of a and b: \n");
    scanf("%d %d", &a, &b);
    printf("Before swapping a=%d, b=%d\n", a,b);
    /*Swapping logic */
    a = a + b;
    b = a - b;
    a = a - b;
    printf("After swapping a=%d b=%d\n", a, b);
    return 0;
    }
    Output:
    Enter values of a and b: 2 3
    Before swapping a=2, b=3
    The values after swapping are a=3 b=2


    5. Write a program to swap two numbers using bitwise operators.
    Program:
    #include <stdio.h>
    int main() {
    int i = 65;
    int k = 120;
    printf("\n value of i=%d k=%d before swapping", i, k);
    i = i ^ k;
    k = i ^ k;
    i = i ^ k;
    printf("\n value of i=%d k=%d after swapping", i, k);
    return 0;
    }
    Explanation:
    i = 65; binary equivalent of 65 is 0100 0001
    k = 120; binary equivalent of 120 is 0111 1000
    i = i^k;
    i...0100 0001
    k...0111 1000
    ---------
    val of i = 0011 1001
    ---------
    k = i^k
    i...0011 1001
    k...0111 1000
    ---------
    val of k = 0100 0001 binary equivalent of this is 65
    ---------(that is the initial value of i)
    i = i^k
    i...0011 1001
    k...0100 0001
    ---------
    val of i = 0111 1000 binary equivalent of this is 120
    --------- (that is the initial value of k)


    6. Write a program to find the greatest of three numbers.
    Program:
    #include <stdio.h>
    int main(){
    int a, b, c;
    printf("Enter a,b,c: \n");
    scanf("%d %d %d", &a, &b, &c);
    if (a > b && a > c) {
    printf("a is Greater than b and c");
    }
    else if (b > a && b > c) {
    printf("b is Greater than a and c");
    }
    else if (c > a && c > b) {
    printf("c is Greater than a and b");
    }
    else {
    printf("all are equal or any two values are equal");
    }
    return 0;
    }
    Output:
    Enter a,b,c: 3 5 8
    c is Greater than a and b
    Explanation with examples:
    Consider three numbers a=5,b=4,c=8
    if(a>b && a>c) then a is greater than b and c
    now check this condition for the three numbers 5,4,8 i.e.
    if(5>4 && 5>8) /* 5>4 is true but 5>8 fails */
    so the control shifts to else if condition
    else if(b>a && b>c) then b is greater than a and c
    now checking this condition for 5,4,8 i.e.
    else if(4>5 && 4>8) /* both the conditions fail */
    now the control shifts to the next else if condition
    else if(c>a && c>b) then c is greater than a and b
    now checking this condition for 5,4,8 i.e.
    else if(8>5 && 8>4) /* both conditions are satisfied */
    Thus c is greater than a and b.


    7. Write a program to find the greatest among ten numbers.
    Program:
    #include <stdio.h>
    int main() {
    int a[10];
    int i;
    int greatest;
    printf("Enter ten values:");
    //Store 10 numbers in an array
    for (i = 0; i < 10; i++) {
    scanf("%d", &a[i]);
    }
    //Assume that a[0] is greatest
    greatest = a[0];
    for (i = 0; i < 10; i++) {
    if (a[i] > greatest) {
    greatest = a[i];
    }
    }
    printf("\nGreatest of ten numbers is %d", greatest);
    return 0;
    }
    Output:
    Enter ten values: 2 53 65 3 88 8 14 5 77 64 Greatest of ten numbers is 88
    Explanation with example:
    Entered values are 2, 53, 65, 3, 88, 8, 14, 5, 77, 64
    They are stored in an array of size 10. let a[] be an array holding these values.
    /* how the greatest among ten numbers is found */
    Let us consider a variable 'greatest'. At the beginning of the loop, variable 'greatest' is assinged with the value of
    first element in the array greatest=a[0]. Here variable 'greatest' is assigned 2 as a[0]=2.
    Below loop is executed until end of the array 'a[]';.
    for(i=0; i<10; i++)
    {
    if(a[i]>greatest)
    {
    greatest= a[i];
    }
    }
    For each value of 'i', value of a[i] is compared with value of variable 'greatest'. If any value greater than the value
    of 'greatest' is encountered, it would be replaced by a[i]. After completion of 'for' loop, the value of variable
    'greatest' holds the greatest number in the array. In this case 88 is the greatest of all the numbers.


    8. Write a program to check whether the given number is a prime.
    A prime number is a natural number that has only one and itself as factors. Examples: 2, 3, 13 are prime
    numbers.
    Program:
    #include <stdio.h>
    main() {
    int n, i, c = 0;
    printf("Enter any number n: \n");
    scanf("%d", &n);
    /*logic*/
    for (i = 1; i <= n; i++) {
    if (n % i == 0) {
    c++;
    }
    }
    if (c == 2) {
    printf("n is a Prime number");
    }
    else {
    printf("n is not a Prime number");
    }
    return 0;
    }
    Output:
    Enter any number n: 7
    n is Prime
    Explanation with examples:
    consider a number n=5
    for(i=0;i<=n;i++) /* for loop is executed until the n value equals i */
    i.e. for(i=0;i<=5;i++) /* here the for loop is executed until i is equal to n */
    1st iteration: i=1;i<=5;i++
    here i is incremented i.e. i value for next iteration is 2
    now if(n%i==0) then c is incremented
    i.e.if(5%1==0)then c is incremented, here 5%1=0 thus c is incremented.
    now c=1;
    2nd iteration: i=2;i<=5;i++
    here i is incremented i.e. i value for next iteration is 3
    now if(n%i==0) then c is incremented
    i.e.if(5%2==0) then c is incremented, but 5%2!=0 and so c is not incremented, c remains 1
    c=1;
    3rd iteration: i=3;i<=5;i++
    here i is incremented i.e. i value for next iteration is 4
    now if(n%i==0) then c is incremented
    i.e.if(5%3==0) then c ic incremented, but 5%3!=0 and so c is not incremented, c remains 1
    c=1;
    4th iteration: i=4;i<=5;i++
    here i is incremented i.e. i value for next iteration is 5
    now if(n%i==0) then c is incremented
    i.e. if(5%4==0) then c is incremented, but 5%4!=0 and so c is not incremented, c remains 1
    c=1;
    5th iteration: i=5;i<=5;i++
    here i is incremented i.e. i value for next iteration is 6
    now if(n%i==0) then c is incremented
    i.e. if(5%5==0) then c is incremented, 5%5=0 and so c is incremented.
    i.e. c=2
    6th iteration: i=6;i<=5;i++
    here i value is 6 and 6<=5 is false thus the condition fails and control leaves the for loop.
    now if(c==2) then n is a prime number
    we have c=2 from the 5th iteration and thus n=5 is a Prime number.


    9. Write a program to check whether the given number is a palindromic number.
    If a number, which when read in both forward and backward way is same, then such a number is called a
    palindrome number.
    Program:
    #include <stdio.h>
    int main() {
    int n, n1, rev = 0, rem;
    printf("Enter any number: \n");
    scanf("%d", &n);
    n1 = n;
    /* logic */
    while (n > 0){
    rem = n % 10;
    rev = rev * 10 + rem;
    n = n / 10;
    }
    if (n1 == rev){
    printf("Given number is a palindromic number");
    }
    else{
    printf("Given number is not a palindromic number");
    }
    return 0;
    }
    Output:
    Enter any number: 121
    Given number is a palindrome
    Explanation with an example:
    Consider a number n=121, reverse=0, remainder;
    number=121
    now the while loop is executed /* the condition (n>0) is satisfied */
    /* calculate remainder */
    remainder of 121 divided by 10121%10)=1;
    now reversereverse*10)+remainder
    0*10)+1 /* we have initialized reverse=0 */
    =1
    number=number/10
    =121/10
    =12
    now the number is 12, greater than 0. The above process is repeated for number=12.
    remainder=12%10=2;
    reverse1*10)+2=12;
    number=12/10=1;
    now the number is 1, greater than 0. The above process is repeated for number=1.
    remainder=1%10=1;
    reverse12*10)+1=121;
    number=1/10 /* the condition n>0 is not satisfied,control leaves the while loop */
    Program stops here. The given number=121 equals the reverse of the number. Thus the given number is a
    palindrome number.


    10.Write a program to check whether the given string is a palindrome.
    Palindrome is a string, which when read in both forward and backward way is same.
    Example: radar, madam, pop, lol, rubber, etc.,
    Program:
    #include <stdio.h>
    #include <string.h>
    int main() {
    char string1[20];
    int i, length;
    int flag = 0;
    printf("Enter a string: \n");
    scanf("%s", string1);
    length = strlen(string1);
    for(i=0;i < length ;i++){
    if(string1[i] != string1[length-i-1]){
    flag = 1;
    break;
    }
    }
    if (flag) {
    printf("%s is not a palindrome\n", string1);
    }
    else {
    printf("%s is a palindrome\n", string1);
    }
    return 0;
    }
    Output:
    Enter a string: radar
    "radar" is a palindrome
    Explanation with example:
    To check if a string is a palindrome or not, a string needs to be compared with the reverse of itself.
    Consider a palindrome string: "radar",
    ---------------------------
    index: 0 1 2 3 4
    value: r a d a r
    ---------------------------
    To compare it with the reverse of itself, the following logic is used:
    0th character in the char array, string1 is same as 4th character in the same string.
    1st character is same as 3rd character.
    2nd character is same as 2nd character.
    . . . .
    ith character is same as 'length-i-1'th character.
    If any one of the above condition fails, flag is set to true(1), which implies that the string is not a palindrome.
    By default, the value of flag is false(0). Hence, if all the conditions are satisfied, the string is a palindrome.


    11.Write a program to generate the Fibonacci series.
    Fibonacci series: Any number in the series is obtained by adding the previous two numbers of the series.
    Let f(n) be n'th term.
    f(0)=0;
    f(1)=1;
    f(n)=f(n-1)+f(n-2); (for n>=2)
    Series is as follows
    011
    (1+0)
    2 (1+1)
    3 (1+2)
    5 (2+3)
    8 (3+5)
    13 (5+8)
    21 (8+13)
    34 (13+21)
    ...and so on
    Program: to generate Fibonacci Series(10 terms)
    #include<stdio.h>
    int main() {
    //array fib stores numbers of fibonacci series
    int i, fib[25];
    //initialized first element to 0
    fib[0] = 0;
    //initialized second element to 1
    fib[1] = 1;
    //loop to generate ten elements
    for (i = 2; i < 10; i++) {
    //i'th element of series is equal to the sum of i-1'th element and i-2'th element.
    fib[i] = fib[i - 1] + fib[i - 2];
    }
    printf("The fibonacci series is as follows \n");
    //print all numbers in the series
    for (i = 0; i < 10; i++) {
    printf("%d \n", fib[i]);
    }
    return 0;
    }
    Output:
    The fibonacci series is as follows
    01123581
    3
    21
    34
    Explanation:
    The first two elements are initialized to 0, 1 respectively. Other elements in the series are generated by looping
    and adding previous two numbes. These numbers are stored in an array and ten elements of the series are
    printed as output.


    12.Write a program to print "Hello World" without using semicolon anywhere in the code.
    Generally when we use printf("") statement, we have to use a semicolon at the end. If printf is used inside an if
    Condition, semicolon can be avoided.
    Program: Program to print something without using semicolon (;)
    #include <stdio.h>
    int main() {
    //printf returns the length of string being printed
    if (printf("Hello World\n")) //prints Hello World and returns 11
    {
    //do nothing
    }
    return 0;
    }
    Output:
    Hello World
    Explanation:
    The if statement checks for condition whether the return value of printf("Hello World") is greater than 0. printf
    function returns the length of the string printed. Hence the statement if (printf("Hello World")) prints the string
    "Hello World".


    13.Write a program to print a semicolon without using a semicolon anywhere in the code.
    Generally when use printf("") statement we have to use semicolon at the end.
    If we want to print a semicolon, we use the statement: printf(";");
    In above statement, we are using two semicolons. The task of printing a semicolon without using semicolon anywhere in the code can be accomplished by using the ascii value of ' ; ' which is equal to 59.
    Program: Program to print a semicolon without using semicolon in the code.
    #include <stdio.h>
    int main(void) {
    //prints the character with ascii value 59, i.e., semicolon
    if (printf("%c\n", 59)) {
    //prints semicolon
    }
    return 0;
    }
    Output:
    ;
    Explanation:
    If statement checks whether return value of printf function is greater than zero or not. The return value of function
    call printf("%c",59) is 1. As printf returns the length of the string printed. printf("%c",59) prints ascii value that
    corresponds to 59, that is semicolon(;).


    14.Write a program to compare two strings without using strcmp() function.
    strcmp() function compares two strings lexicographically. strcmp is declared in stdio.h
    Case 1: when the strings are equal, it returns zero.
    Case 2: when the strings are unequal, it returns the difference between ascii values of the characters that differ.
    a) When string1 is greater than string2, it returns positive value.
    b) When string1 is lesser than string2, it returns negative value.
    Syntax:
    int strcmp (const char *s1, const char *s2);
    Program: to compare two strings.
    #include<stdio.h>
    #include<string.h>
    int cmpstr(char s1[10], char s2[10]);
    int main() {
    char arr1[10] = "Nodalo";
    char arr2[10] = "nodalo";
    printf(" %d", cmpstr(arr1, arr2));
    //cmpstr() is equivalent of strcmp()
    return 0;
    }/
    /s1, s2 are strings to be compared
    int cmpstr(char s1[10], char s2[10]) {
    //strlen function returns the length of argument string passed
    int i = strlen(s1);
    int k = strlen(s2);
    int bigger;
    if (i < k) {
    bigger = k;
    }
    else if (i > k) {
    bigger = i;
    }
    else {
    bigger = i;
    }
    //loops 'bigger' times
    for (i = 0; i < bigger; i++) {
    //if ascii values of characters s1[i], s2[i] are equal do nothing
    if (s1[i] == s2[i]) {
    }
    //else return the ascii difference
    else {
    return (s1[i] - s2[i]);
    }
    }
    //return 0 when both strings are same
    //This statement is executed only when both strings are equal
    return (0);
    }
    Output:
    -32
    Explanation:
    cmpstr() is a function that illustrates C standard function strcmp(). Strings to be compared are sent as arguments
    to cmpstr().
    Each character in string1 is compared to its corresponding character in string2. Once the loop encounters a
    differing character in the strings, it would return the ascii difference of the differing characters and exit.


    15.Write a program to concatenate two strings without using strcat() function.
    strcat(string1,string2) is a C standard function declared in the header file string.h
    The strcat() function concatenates string2, string1 and returns string1.
    Program: Program to concatenate two strings
    #include<stdio.h>
    #include<string.h>
    char *strct(char *c1, char *c2);
    char *strct(char *c1, char *c2) {
    //strlen function returns length of argument string
    int i = strlen(c1);
    int k = 0;
    //loops until null is encountered and appends string c2 to c1
    while (c2[k] != '\0') {
    c1[i + k] = c2[k];
    k++;
    }
    return c1;
    }
    int main() {
    char string1[15] = "first";
    char string2[15] = "second";
    char *finalstr;
    printf("Before concatenation:"
    " \n string1 = %s \n string2 = %s", string1, string2);
    //addresses of string1, string2 are passed to strct()
    finalstr = strcat(string1, string2);
    printf("\nAfter concatenation:");
    //prints the contents of string whose address is in finalstr
    printf("\n finalstr = %s", finalstr);
    //prints the contents of string1
    printf("\n string1 = %s", string1);
    //prints the contents of string2
    printf("\n string2 = %s", string2);
    return 0;
    }
    Output:
    Before concatenation:
    string1 = first
    string2 = second
    After concatenation:
    finalstr = firstsecond
    string1 = firstsecond
    string2 = second
    Explanation:
    string2 is appended at the end of string1 and contents of string2 are unchanged.
    In strct() function, using a for loop, all the characters of string 'c2' are copied at the end of c1. return (c1) is
    equivalent to return &c1[0] and it returns the base address of 'c1'. 'finalstr' stores that address returned by the
    function strct().


    16.Write a program to delete a specified line from a text file.
    In this program, user is asked for a filename he needs to change. User is also asked for the line number that is
    to be deleted. The filename is stored in 'filename'. The file is opened and all the data is transferred to another file
    except that one line the user specifies to delete.
    Program: Program to delete a specific line.
    #include <stdio.h>
    int main() {
    FILE *fp1, *fp2;
    //consider 40 character string to store filename
    char filename[40];
    char c;
    int del_line, temp = 1;
    //asks user for file name
    printf("Enter file name: ");
    //receives file name from user and stores in 'filename'
    scanf("%s", filename);
    //open file in read mode
    fp1 = fopen(filename, "r");
    c = getc(fp1);
    //until the last character of file is obtained
    while (c != EOF)
    {
    printf("%c", c);
    //print current character and read next character
    c = getc(fp1);
    }
    //rewind
    rewind(fp1);
    printf(" \n Enter line number of the line to be deleted:");
    //accept number from user.
    scanf("%d", &del_line);
    //open new file in write mode
    fp2 = fopen("copy.c", "w");
    c = getc(fp1);
    while (c != EOF) {
    c = getc(fp1);
    if (c == '\n')
    temp++;
    //except the line to be deleted
    if (temp != del_line)
    {
    //copy all lines in file copy.c
    putc(c, fp2);
    }
    }
    //close both the files.
    fclose(fp1);
    fclose(fp2);
    //remove original file
    remove(filename);
    //rename the file copy.c to original name
    rename("copy.c", filename);
    printf("\n The contents of file after being modified are as follows:\n");
    fp1 = fopen(filename, "r");
    c = getc(fp1);
    while (c != EOF) {
    printf("%c", c);
    c = getc(fp1);
    }
    fclose(fp1);
    return 0;
    }
    Output:
    Enter file name:abc.txt
    hi.
    Hello
    how are you?
    I am fine
    hope the same
    Enter line number of the line to be deleted:4
    The contents of file after being modified are as follows:
    hi.
    hello
    how are you?
    hope the same
    Explanation:
    In this program, user is asked for a filename that needs to be modified. Entered file name is stored in a char
    array 'filename'. This file is opened in read mode using file pointer 'fp1'. Character 'c' is used to read characters
    from the file and print them to the output. User is asked for the line number in the file to be deleted. The file
    pointer is rewinded back and all the lines of the file except for the line to be deleted are copied into another file
    "copy.c". Now "copy.c" is renamed to the original filename. The original file is opened in read mode and the
    modified contents of the file are displayed on the screen.





    17.Write a program to replace a specified line in a text file.
    Program: Program to replace a specified line in a text file.
    #include <stdio.h>
    int main(void) {
    FILE *fp1, *fp2;
    //'filename'is a 40 character string to store filename
    char filename[40];
    char c;
    int del_line, temp = 1;
    //asks user for file name
    printf("Enter file name: ");
    //receives file name from user and stores in 'filename'
    scanf("%s", filename);
    fp1 = fopen(filename, "r");
    //open file in read mode
    c = getc(fp1);
    //print the contents of file .
    while (c != EOF) {
    printf("%c", c);
    c = getc(fp1);
    }
    //ask user for line number to be deleted.
    printf(" \n Enter line number to be deleted and replaced");
    scanf("%d", &del_line);
    //take fp1 to start point.
    rewind(fp1);
    //open copy.c in write mode
    fp2 = fopen("copy.c", "w");
    c = getc(fp1);
    while (c != EOF) {
    if (c == '\n') {
    temp++;
    }
    //till the line to be deleted comes,copy the content from one file to other
    if (temp != del_line){
    putc(c, fp2);
    }
    else //when the line to be deleted comes
    {
    while ((c = getc(fp1)) != '\n') {
    }
    //read and skip the line ask for new text
    printf("Enter new text");
    //flush the input stream
    fflush(stdin);
    putc('\n', fp2);
    //put '\n' in new file
    while ((c = getchar()) != '\n')
    putc(c, fp2);
    //take the data from user and place it in new file
    fputs("\n", fp2);
    temp++;
    }
    //continue this till EOF is encountered
    c = getc(fp1);
    }
    //close both files
    fclose(fp1);
    fclose(fp2);
    //remove original file
    remove(filename);
    //rename new file with old name opens the file in read mode
    rename("copy.c", filename);
    fp1 = fopen(filename, "r");
    //reads the character from file
    c = getc(fp1);
    //until last character of file is encountered
    while (c != EOF){
    printf("%c", c);
    //all characters are printed
    c = getc(fp1);
    }
    //close the file pointer
    fclose(fp1);
    return 0;
    }
    Output:
    Enter file name:abc.txt
    hi.
    hello
    how are you?
    hope the same
    Enter line number of the line to be deleted and replaced:4
    Enter new text: sayonara see you soon
    hi.
    hello
    how are you?
    sayonara see you soon
    Explanation:
    In this program, the user is asked to type the name of the file. The File by name entered by user is opened in
    read mode. The line number of the line to be replaced is asked as input. Next the data to be replaced is asked. A
    new file is opened in write mode named "copy.c". Now the contents of original file are transferred into new file
    and the line to be modified is deleted. New data is stored in its place and remaining lines of the original file are
    also transferred. The copied file with modified contents is replaced with the original file's name. Both the file
    pointers are closed and the original file is again opened in read mode and the contents of the original file is
    printed as output.


    18.Write a program to find the number of lines in a text file.
    Number of lines in a file can be determined by counting the number of new line characters present.
    Program: Program to count number of lines in a file.
    #include <stdio.h>
    int main()
    /* Ask for a filename and count number of lines in the file*/
    {
    //a pointer to a FILE structure
    FILE *fp;
    int no_lines = 0;
    //consider 40 character string to store filename
    char filename[40], sample_chr;
    //asks user for file name
    printf("Enter file name: ");
    //receives file name from user and stores in a string named 'filename'
    scanf("%s", filename);
    //open file in read mode
    fp = fopen(filename, "r");
    //get character from file and store in sample_chr
    sample_chr = getc(fp);
    while (sample_chr != EOF) {
    //Count whenever sample_chr is '\n'(new line) is encountered
    if (sample_chr == '\n')
    {
    //increment variable 'no_lines' by 1
    no_lines=no_lines+1;
    }
    //take next character from file.
    sample_chr = getc(fp);
    }
    fclose(fp); //close file.
    printf("There are %d lines in %s \n", no_lines, filename);
    return 0;
    }
    Output:
    Enter file name:abc.txt
    There are 4 lines in abc.txt
    Explanation:
    In this program, name of the file to be read is taken as input. A file by the given name is opened in read-mode
    using a File pointer 'fp'. Characters from the file are read into a char variable 'sample_chr' with the help of getc
    function. If a new line character('\n') is encountered, the integer variable 'no_lines' is incremented. If the
    character read into 'sample_char' is not a new line character, next character is read from the file. This process is
    continued until the last character of the file(EOF) is encountered. The file pointer is then closed and the total
    number of lines is shown as output.





    19.Write a C program which asks the user for a number between 1 to 9 and shows the number. If the
    user inputs a number out of the specified range, the program should show an error and prompt
    the user for a valid input.
    Program: Program for accepting a number in a given range.
    #include<stdio.h>
    int getnumber();
    int main() {
    int input = 0;
    //call a function to input number from key board
    input = getnumber();
    //when input is not in the range of 1 to 9,print error message
    while (!((input <= 9) && (input >= 1))) {
    printf("[ERROR] The number you entered is out of range");
    //input another number
    input = getnumber();
    }
    //this function is repeated until a valid input is given by user.
    printf("\nThe number you entered is %d", input);
    return 0;
    }/
    /this function returns the number given by user
    int getnumber() {
    int number;
    //asks user for a input in given range
    printf("\nEnter a number between 1 to 9 \n");
    scanf("%d", &number);
    return (number);
    }
    Output:
    Enter a number between 1 to 9
    45
    [ERROR] The number you entered is out of range
    Enter a number between 1 to 9
    4
    The number you entered is 4
    Explanation:
    getfunction() function accepts input from user. 'while' loop checks whether the number falls within range or not
    and accordingly either prints the number(If the number falls in desired range) or shows error message(number is
    out of range).
    20.Write a program to display the multiplication table of a given number.
    Program: Multiplication table of a given number
    #include <stdio.h>
    int main() {
    int num, i = 1;
    printf("\n Enter any Number:");
    scanf("%d", &num);
    printf("Multiplication table of %d: \n", num);
    while (i <= 10) {
    printf("\n %d x %d = %d", num, i, num * i);
    i++;
    }
    return 0;
    }
    Output:
    Enter any Number:5
    5 x 1 = 5
    5 x 2 = 10
    5 x 3 = 15
    5 x 4 = 20
    5 x 5 = 25
    5 x 6 = 30
    5 x 7 = 35
    5 x 8 = 40
    5 x 9 = 45
    5 x 10 = 50
    Explanation:
    We need to multiply the given number (i.e. the number for which we want the multiplication table)
    with value of 'i' which increments from 1 to 10.

    21. .WAP to check a string is Caliondrome or not. //Maventic question.
    #include<stdio.h>
    #include<conio.h>
    void main()
    {
    int i,j=0; char a[100];
    clrscr();
    printf("\nEnter the string to check for caliondrome:\n");
    gets(a);

    if(strlen(a)%6)
    {
    printf("\n%s: is Not a caliondrome..",a);
    getch();
    exit(0);
    }
    for (i=0;a[i]!='\0';)
    {
    if((a[i]==a[i+5])&&(a[i+1]==a[i+4])&&(a[i+2]==a[i+3]))
    i=i+6;

    else
    {
    j=1;
    break;
    }
    }
    if(j)
    printf("\n%s: is Not a caliondrome..",a);
    else
    printf("\n%s: is a caliondrome..",a);
    getch();
    }

    22.WAP to print DONE,without using any loop. // asked to my frnd in any company.
    #include<conio.h>
    void main()
    {
    static int i=0;
    printf("\n%d. DONE ",i);
    if(i++<100)
    main();
    getch();
    exit(0); /* I used exit(0) to terminate the program after 100 DONE,,i dunno why it was not terminating without using it,may be just at my system,try without it at ur sustem,it sud work */
    }

    23.WAP to print DONE,without using any loop and any conditonal clause or operators.

    /* This code is just in purpose to solve the above question,,but its not a good code in programming,as its terminating at divide error,,if anyone have a better code,let me know */

    main()
    {
    static int i=100;
    printf("%d. DONE\n",101-i);
    main(1/--i);
    }

    /* use "ctrl+f9" ,then "alt+f5" to see the result */


    24. WAP to find out the longest word in a string.
    #include<stdio.h>
    #include<string.h>
    #include<conio.h>
    void main()
    {
    int i,max=0,count=0,j;
    char str[100]; /* ={"INDIA IS DEMOCRATIC COUNTRY"}; u can use a string inside,in place of user input */

    printf("\nEnter the string\n:");
    gets(str);
    for(i=0;i<strlen(str);i++)
    {
    if(!(str[i]==32))
    {
    count++;
    }
    else
    {
    if(max<count)
    {
    j=i-count;
    max=count;
    }
    count=0;
    }
    }
    for(i=j;i<(j+max);i++)
    printf("%c",str[i]);
    getch();
    }

    25.Prog of WORLD MAP.
    #include<conio.h> main(l ,a,n,d)char**a;{ for(d=atoi(a[1])/10*80- atoi(a[2])/5-596;n="@NKA\CLCCGZAAQBEAADAFaISADJABBA^\SNLGAQABDA XIMBAACTBATAHDBAN\ZcEMMCCCCAAhEIJFAEAAABAfHJE\TBdF LDAANEfDNBPHdBcBBBEA_AL\ H E L L O, W O R L D! " [l++-3];)for(;n-->64;) putchar(!d+++33^ l&1);printf("\n\n\n\n\t\tFound By:\n\t\t\t Amit Aru");getch();}


    26.WAP to print the triangle of letters in increasing order of lines.

    #include<stdio.h>
    #include<conio.h>
    void main()
    {
    int i,j,k;
    char ch;
    printf("\nEnter the number of lines wants to make the triangle \n: ");
    scanf("%d",&i);
    for(j=1;j<=i;j++)
    {
    ch=65;
    for(k=1;k<=j;k++)
    {
    printf("%c",ch++);
    }
    printf("\n");
    }
    getch();
    }

    27.WAP to print 'xay' in place of every 'a' in a string.

    #include<stdio.h>
    #include<conio.h>
    void main()
    {
    int i=0;
    char str[100],x='x',y='y';
    printf("Enter the string\n: ");
    gets(str);
    while(str[i]!='\0')
    {
    if(str[i]=='a')
    {
    printf("%c",x);
    printf("%c",str[i++]);
    printf("%c",y);
    }
    else
    {
    printf("%c",str[i++]);
    }
    }
    getch();
    }

    28.Count the Total Number of 7 comming between 1 to 100.

    /* I made this code in a way that u can give Upper limit i.e. 100,Lower limit i.e. 1 and the specific number u wants to count in between i.e. 7 */

    #include<stdio.h>
    #include<conio.h>
    void main()
    {
    int i,j,U=100,L=1,count=0,r=1,n;
    clrscr();
    printf("\nEnter the number u wants to count\n: ");
    scanf("%d",&n);
    printf("\nEnter the lower limit\n: ");
    scanf("%d",&L);
    printf("\nEnter the upper limit\n: ");
    scanf("%d",&U);

    for (i=L;i<=U;i++)
    {
    j=i;
    while(j)
    {
    r=j%10;
    if (r==n)
    {
    count++;
    }
    j=j/10;
    }
    }
    if(n==0&&L==0)
    count++;
    printf("\nTotal Number of %d between %d and %d = %d",n,L,U,count);
    getch();
    }


    29. Code for duplicate's removal,by Amit Aru.
    #include<stdio.h>
    #include<conio.h>
    void main()
    {
    int i,j,k=0,count[300]={0};
    char ch,str[1000],str1[1000];
    clrscr();
    printf("\nEnter the string to remove duplicasy\n: ");
    gets(str);
    for (i=0;str[i]!='\0';i++)
    {
    ch=str[i];
    count[' ']=0; /* U can use other delimiter inplace of space ' ' here,just put that char inside ' ' ,for ex: count['A']=0; if u dnt want any delimiter,just remove this line.*/

    if(count[ch])
    continue;
    else
    {
    str1[k++]=ch;
    count[ch]=1;
    }
    }
    puts(str1);
    getch();
    }

    30. WAP to find out if a given number is a power series of 2 or not,without any loop and without using % modulo operator.

    #include<stdio.h>
    #include<conio.h>
    int pow2(float);
    void main()
    {
    int i,flag;
    clrscr();
    printf("Enter the number\n");
    scanf("%d",&i);
    flag=pow2(i);
    if(flag)
    printf("\n%d is power series of 2",i);
    else
    printf("\n%d is not a power series of 2",i);
    getch();
    }

    int pow2(float j)
    {
    static float x;
    x=j/2;
    if(x==2)
    return 1;
    if(x<2)
    return 0;
    x=pow2(x);
    }
    Autograph Your Every Work with Excellence.

  2. #2

    Re: Important C Programs With Solutions

    Hi there,
    Thanks a lot for sharing c language programs and solution. When I was in college then I felt a lot of difficulties in programming now I came to know that this is not so tough to do programming. Basically practice and basic concept must be clear. Because it is not possible to make a c program without explaning its basic concept.

  3. #3

    Re: Important C Programs With Solutions

    Hi friend...

    Thank you so much for the sharing... too very informative

    i have a request.. can u plz explain me the 21st program((WAP to check a string is Caliondrome or not. ))
    wat iz calindrome?? is it something related to palindrome???
    plz reply ASAP
    techforum4u.com Member!!

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