String length

This program prints length of string, for example consider the string "c programming" it's length is 13. Null character is not counted when calculating string length. To find string length we use strlen function of string.h.

C program to find string length

#include<stdio.h>
#include<string.h>
 
main()
{
   char a[100];
   int length;
 
   printf("Enter a string to calculate it's length\n");
   gets(a);
 
   length = strlen(a);
 
   printf("Length of entered string is = %d\n",length);
 
   return 0;
}

You can also find string length using pointer or without strlen function. Following program shows how to achieve this.

C program to find string length without strlen

C program to find length of a string using pointers.

#include<stdio.h>
 
main()
{
   char array[100], *pointer;
   int length = 0;
 
   printf("Enter a string\n");
   gets(array);
 
   pointer = array;
 
   while(*(pointer+length))
      length++;
 
   printf("Length of entered string = %d\n",length);
 
   return 0;
}

Function to find string length

int string_length(char *s)
{
   int c = 0;
 
   while(*(s+c))
      c++;
 
   return c;
}

c program for to add 2 matrix

c program to add two matrix

This c program add two matrices i.e. compute the sum of two matrices and then print it. Firstly user will be asked to enter the order of matrix ( number of rows and columns ) and then two matrices. For example if the user entered order as 2, 2 i.e. two rows and two columns and matrices as
First Matrix :-
1 2
3 4
Second matrix :-
4 5
-1 5
then output of the program ( sum of First and Second matrix ) will be
5 7
2 9

C programming code

#include <stdio.h>
 
main()
{
   int m, n, c, d, first[10][10], second[10][10], sum[10][10];
 
   printf("Enter the number of rows and columns of matrix ");
   scanf("%d%d", &m, &n);
   printf("Enter the elements of first matrix\n");
 
   for ( c = 0 ; c < m ; c++ )
      for ( d = 0 ; d < n ; d++ )
         scanf("%d", &first[c][d]);
 
   printf("Enter the elements of second matrix\n");
 
   for ( c = 0 ; c < m ; c++ )
      for ( d = 0 ; d < n ; d++ )
            scanf("%d", &second[c][d]);
 
   for ( c = 0 ; c < m ; c++ )
      for ( d = 0 ; d < n ; d++ )
         sum[c][d] = first[c][d] + second[c][d];
 
   printf("Sum of entered matrices:-\n");
 
   for ( c = 0 ; c < m ; c++ )
   {
      for ( d = 0 ; d < n ; d++ )
         printf("%d\t", sum[c][d]);
 
      printf("\n");
   }
 
   return 0;
}

Add matrices program. Output of program:

C program to shutdown or turn off computer

C Program to shutdown your computer: This program turn off i.e shutdown your computer system. Firstly it will asks you to shutdown your computer if you press 'y' the your computer will shutdown in 30 seconds, system function of "stdlib.h" is used to run an executable file shutdown.exe which is present in C:\WINDOWS\system32 in Windows XP. You can use various options while executing shutdown.exe for example -s option shutdown the computer after 30 seconds, if you wish to shutdown immediately then you can write "shutdown -s -t 0" as an argument to system function. If you wish to restart your computer then you can write "shutdown -r".

If you are using Turbo C Compiler then execute your file from folder. Press F9 to build your executable file from source program. When you run from within the compiler by pressing Ctrl+F9 it may not work.

C programming code for Windows XP

#include <stdio.h>
#include <stdlib.h>
 
main()
{
   char ch;
 
   printf("Do you want to shutdown your computer now (y/n)\n");
   scanf("%c",&ch);
 
   if (ch == 'y' || ch == 'Y')
      system("C:\\WINDOWS\\System32\\shutdown -s");
 
   return 0;
}

C programming code for Windows 7

#include <stdio.h>
#include <stdlib.h>
 
main()
{
   char ch;
 
   printf("Do you want to shutdown your computer now (y/n)\n");
   scanf("%c",&ch);
 
   if (ch == 'y' || ch == 'Y')
      system("C:\\WINDOWS\\System32\\shutdown /s");
 
   return 0;
}

To shutdown immediately use "C:\\WINDOWS\\System32\\ shutdown /s /t 0". To restart use /r instead of /s.

C programming code for Ubuntu Linux

#include <stdio.h>
 
int main() {
  system("shutdown -P now");
  return 0;
} 

You need to be logged in as root user for above program to execute otherwise you will get the message shutdown: Need to be root, now specifies that you want to shutdown immediately. '-P' option specifes you want to power off your machine. You can specify minutes as:
shutdown -P "number of minutes"
For more help or options type at terminal: man shutdown.

c program to get ip address

This c program prints ip (internet protocol) address of your computer, system function is used to execute the command ipconfig which prints ip address, subnet mask and default gateway. The code given below works for Windows xp and Windows 7. If you are using turbo c compiler then execute program from folder, it may not work when you are working in compiler and press Ctrl+F9 to run your program.

C programming code

#include<stdlib.h>
 
main()
{
   system("C:\\Windows\\System32\\ipconfig");
   system("pause");
 
   return 0;
}

IP address program executable.
Output of program: ( In Windows XP )

c program to print date

This c program prints current system date. To print date we will use getdate function.

C programming code

#include<stdio.h>
#include<conio.h>
#include<dos.h>
 
main()
{
   struct date d;
 
   getdate(&d);
 
   printf("Current system date is %d/%d/%d",d.da_day,d.da_mon,d.da_year);
   getch();
   return 0;
}

Output of program

c program to add two complex numbers

c program to add two complex numbers :- This program calculate the sum of two complex numbers which will be entered by the user and then prints it. User will have to enter the real and imaginary parts of two complex numbers. In our program we will add real parts and imaginary parts of complex numbers and prints the complex number, i is the symbol used for iota. For example if user entered two complex numbers as (1 + 2i) and (4 + 6 i) then output of program will be (5+8i). A structure is used to store complex number.

C programming code

#include <stdio.h>
 
struct complex
{
   int real, img;
};
 
main()
{
   struct complex a, b, c;
 
   printf("Enter a and b where a + ib is the first complex number.\n");
   printf("a = ");
   scanf("%d", &a.real);
   printf("b = ");
   scanf("%d", &a.img);
   printf("Enter c and d where c + id is the second complex number.\n");
   printf("c = ");
   scanf("%d", &b.real);
   printf("d = ");
   scanf("%d", &b.img);
 
   c.real = a.real + b.real;
   c.img = a.img + b.img;
 
   if ( c.img >= 0 )
      printf("Sum of two complex numbers = %d + %di\n",c.real,c.img);
   else
      printf("Sum of two complex numbers = %d %di\n",c.real,c.img);
 
   return 0;
}

Download add complex numbers program executable.
Output of c program to add two complex numbers is shown in image below :-

c program to add two complex numbers

c program to add two complex numbers :- This program calculate the sum of two complex numbers which will be entered by the user and then prints it. User will have to enter the real and imaginary parts of two complex numbers. In our program we will add real parts and imaginary parts of complex numbers and prints the complex number, i is the symbol used for iota. For example if user entered two complex numbers as (1 + 2i) and (4 + 6 i) then output of program will be (5+8i). A structure is used to store complex number.

C programming code

#include <stdio.h>
 
struct complex
{
   int real, img;
};
 
main()
{
   struct complex a, b, c;
 
   printf("Enter a and b where a + ib is the first complex number.\n");
   printf("a = ");
   scanf("%d", &a.real);
   printf("b = ");
   scanf("%d", &a.img);
   printf("Enter c and d where c + id is the second complex number.\n");
   printf("c = ");
   scanf("%d", &b.real);
   printf("d = ");
   scanf("%d", &b.img);
 
   c.real = a.real + b.real;
   c.img = a.img + b.img;
 
   if ( c.img >= 0 )
      printf("Sum of two complex numbers = %d + %di\n",c.real,c.img);
   else
      printf("Sum of two complex numbers = %d %di\n",c.real,c.img);
 
   return 0;
}

Download add complex numbers program executable.
Output of c program to add two complex numbers is shown in image below :-

c program to generate random numbers

This c program generates random numbers using random function, randomize function is used to initialize random number generator. If you don't use randomize function then you will get same random numbers each time you run the program.

C programming code using rand

#include <stdio.h>
#include <stdlib.h>
 
int main() {
  int c, n;
 
  printf("Ten random numbers in [1,100]\n");
 
  for (c = 1; c <= 10; c++) {
    n = rand()%100 + 1;
    printf("%d\n", n);
  }
 
  return 0;
}

C programming code using random function(Turbo C compiler only)

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
 
main()
{
   int n, max, num, c;
 
   printf("Enter the number of random numbers you want ");
   scanf("%d",&n);
 
   printf("Enter the maximum value of random number ");
   scanf("%d",&max);
 
   printf("%d random numbers from 0 to %d are :-\n",n,max);
   randomize();
 
   for ( c = 1 ; c <= n ; c++ )
   {
      num = random(max);
      printf("%d\n",num);
 
   }
 
   getch();
   return 0;
}

c program to delete a file

This c program deletes a file which is entered by the user, the file to be deleted should be present in the directory in which the executable file of this program is present. Extension of the file should also be entered, also note that deleted file doesn't go to recycle bin, remove macro is used to delete the file. If there is an error in deleting the file then an error will be displayed using perror function.

C programming code

#include<stdio.h>
 
main()
{
   int status;
   char file_name[25];
 
   printf("Enter the name of file you wish to delete\n");
   gets(file_name);
 
   status = remove(file_name);
 
   if( status == 0 )
      printf("%s file deleted successfully.\n",file_name);
   else
   {
      printf("Unable to delete the file\n");
      perror("Error");
   }
 
   return 0;
}

Delete file program executable. Output of program:

c program to list files in directory

This program list all files present in a directory/folder in which this executable file is present. For example if this executable file is present in C:\\TC\\BIN then it will lists all the files present in C:\\TC\\BIN.

C programming code

#include<stdio.h>
#include<conio.h>
#include<dir.h>
 
main()
{
   int done;
   struct ffblk a;
 
   printf("Press any key to view the files in the current directory\n");
 
   getch();
 
   done = findfirst("*.*",&a,0);
 
   while(!done)
   {
      printf("%s\n",a.ff_name);
      done = findnext(&a);
   }
 
   getch();
   return 0;
}

Download list files program executable.
Output c program to list files is shown in image below :-


Obviously you will get a different output when you will execute this file on your computer.

c program to merge two files

This c program merges two files and store their contents in an another file. The files which are to be merged are opened in read mode and the file which contains content of both the files is opened in write mode. To merge two files first we open a file and read it character by character and store the read contents in another file then we read the contents of another file and store it in file, we read two files until EOF ( end of file ) is reached.

C programming code

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
 
main()
{
   FILE *fs1, *fs2, *ft;
 
   char ch, file1[20], file2[20], file3[20];
 
   printf("Enter name of first file ");
   gets(file1);
 
   printf("Enter name of second file ");
   gets(file2);
 
   printf("Enter name of file which will store contents of two files ");
   gets(file3);
 
   fs1 = fopen(file1,"r");
   fs2 = fopen(file2,"r");
 
   if( fs1 == NULL || fs2 == NULL )
   {
      perror("Error ");
      printf("Press any key to exit...\n");
      getch();
      exit(EXIT_FAILURE);
   }
 
   ft = fopen(file3,"w");
 
   if( ft == NULL )
   {
      perror("Error ");
      printf("Press any key to exit...\n");
      exit(EXIT_FAILURE);
   }
 
   while( ( ch = fgetc(fs1) ) != EOF )
      fputc(ch,ft);
 
   while( ( ch = fgetc(fs2) ) != EOF )
      fputc(ch,ft);
 
   printf("Two files were merged into %s file successfully.\n",file3);
 
   fclose(fs1);
   fclose(fs2);
   fclose(ft);
 
   getch();
   return 0;
}

Click here to download executable file of the above program.
Output of above program is shown in image below :-

c program to copy files

C program to copy files: This program copies a file, firstly you will specify the file to copy and then you will enter the name of target file, You will have to mention the extension of file also. We will open the file that we wish to copy in read mode and target file in write mode.

C programming code

#include <stdio.h>
#include <stdlib.h>
 
main()
{
   char ch, source_file[20], target_file[20];
   FILE *source, *target;
 
   printf("Enter name of file to copy\n");
   gets(source_file);
 
   source = fopen(source_file, "r");
 
   if( source == NULL )
   {
      printf("Press any key to exit...\n");
      exit(EXIT_FAILURE);
   }
 
   printf("Enter name of target file\n");
   gets(target_file);
 
   target = fopen(target_file, "w");
 
   if( target == NULL )
   {
      fclose(source);
      printf("Press any key to exit...\n");
      exit(EXIT_FAILURE);
   }
 
   while( ( ch = fgetc(source) ) != EOF )
      fputc(ch, target);
 
   printf("File copied successfully.\n");
 
   fclose(source);
   fclose(target);
 
   return 0;
}

File copy program executable.
Output of the above program is shown in image below :-

c program to read a file

C program to read a file :- This program reads a file entered by the user and displays it's contents on the screen, fopen function is used to open a file, it returns a pointer to structure FILE. FILE is a predefined structure in stdio.h . If the file is successfully opened then fopen returns a pointer to file and if it is unable to open a file then it returns NULL. fgetc function returns a character which is read from the file and fclose function closes the file. Opening a file means we bring file from disk to ram to perform operations on it. The file must be present in the directory in which the executable file of this code sis present.

C program to open a file

C programming code to open a file and to print it contents on screen.

#include<stdio.h>
#include<stdlib.h>
 
main()
{
   char ch, file_name[25];
   FILE *fp;
 
   printf("Enter the name of file you wish to see ");
   gets(file_name);
 
   fp = fopen(file_name,"r"); // read mode
 
   if( fp == NULL )
   {
      perror("Error while opening the file.\n");
      exit(EXIT_FAILURE);
   }
 
   printf("The contents of %s file are :- \n\n", file_name);
 
   while( ( ch = fgetc(fp) ) != EOF )
      printf("%c",ch);
 
   fclose(fp);
   return 0;
}

Read file program executable.

Output of program:

anagram in c

Anagram in c: c program to check whether two strings are anagrams or not, string is assumed to consist of alphabets only. Two words are said to be anagrams of each other if the letters from one word can be rearranged to form the other word. From the above definition it is clear that two strings are anagrams if all characters in both strings occur same number of times. For example "abc" and "cab" are anagram strings, here every character 'a', 'b' and 'c' occur only one time in both strings. Our algorithm tries to find how many times characters appears in the strings and then comparing their corresponding counts.

C anagram programming code

#include <stdio.h>
 
int check_anagram(char [], char []);
 
int main()
{
   char a[100], b[100];
   int flag;
 
   printf("Enter first string\n");
   gets(a);
 
   printf("Enter second string\n");
   gets(b);
 
   flag = check_anagram(a, b);
 
   if (flag == 1)
      printf("\"%s\" and \"%s\" are anagrams.\n", a, b);
   else
      printf("\"%s\" and \"%s\" are not anagrams.\n", a, b);
 
   return 0;
}
 
int check_anagram(char a[], char b[])
{
   int first[26] = {0}, second[26] = {0}, c = 0;
 
   while (a[c] != '\0')
   {
      first[a[c]-'a']++;
      c++;
   }
 
   c = 0;
 
   while (b[c] != '\0')
   {
      second[b[c]-'a']++;
      c++;
   }
 
   for (c = 0; c < 26; c++)
   {
      if (first[c] != second[c])
         return 0;
   }
 
   return 1;
}

Compiler used: 

GCC

Output of program: 

c program to find frequency of characters in a string

This program computes frequency of characters in a string i.e. which character is present how many times in a string. For example in the string "code" each of the character 'c', 'o', 'd', and 'e' has occurred one time. Only lower case alphabets are considered, other characters ( uppercase and special characters ) are ignored. You can easily modify this program to handle uppercase and special symbols.

C programming code

#include<stdio.h>
#include<string.h>
 
main()
{
   char string[100], ch;
   int c = 0, count[26] = {0};
 
   printf("Enter a string\n");
   gets(string);
 
   while ( string[c] != '\0' )
   {
      /* Considering characters from 'a' to 'z' only */
 
      if ( string[c] >= 'a' && string[c] <= 'z' ) 
         count[string[c]-'a']++;
 
      c++;
   }
 
   for ( c = 0 ; c < 26 ; c++ )
   {
      if( count[c] != 0 )
         printf("%c occurs %d times in the entered string.\n",c+'a',count[c]);
   }
 
   return 0;
}

Output of program:

c program to swap two strings

C program to swap strings.

C programming code

#include<stdio.h>
#include<string.h>
#include<malloc.h>
#include<conio.h>
 
main()
{
   char first[100], second[100], *temp;
 
   printf("Enter the first string ");
   gets(first);
 
   printf("Enter the second string ");
   gets(second);
 
   printf("\nBefore Swapping\n");
   printf("First string: %s\n",first);
   printf("Second string: %s\n\n",second);
 
   temp = (char*)malloc(100); 
 
   strcpy(temp,first);
   strcpy(first,second);
   strcpy(second,temp);
 
   printf("After Swapping\n");
   printf("First string: %s\n",first);
   printf("Second string: %s\n",second);
 
   getch();
   return 0;
}

Output of program

Swap strings program executable.

Change lower to upper case in c

strlwr, strupr in c

Here we will change string case with and without strlwr, strupr functions.

strlwr in c

#include<stdio.h>
#include<string.h>
 
main()
{
    char string[] = "Strlwr in C";
 
    printf("%s\n",strlwr(string));
 
    return  0;
}

strupr in c

#include<stdio.h>
#include<string.h>
 
main()
{
    char string[] = "strupr in c";
 
    printf("%s\n",strupr(string));
 
    return  0;
}

Change string to upper case without strupr

#include<stdio.h>
 
void upper_string(char*);
 
main()
{
   char string[100];
 
   printf("Enter a string to convert it into upper case\n");
   gets(string);
 
   upper_string(string);
 
   printf("Entered string in upper case is \"%s\"\n", string);
 
   return 0;
}
 
void upper_string(char *string)
{
   while(*string)
   {
       if ( *string >= 'a' && *string <= 'z' )
       {
          *string = *string - 32;
       }
       string++;
   }
}

Change string to lower case without strlwr

#include<stdio.h>
 
void lower_string(char*);
 
main()
{
   char string[100];
 
   printf("Enter a string to convert it into lower case\n");
   gets(string);
 
   lower_string(string);
 
   printf("Entered string in lower case is \"%s\"\n", string);
 
   return 0;
}
 
void lower_string(char *string)
{
   while(*string)
   {
      if ( *string >= 'A' && *string <= 'Z' )
      {
         *string = *string + 32;
      }
      string++;
   }
}

c program remove spaces, blanks from a string

C code to remove spaces or excess blanks from a string, For example consider the string

"c  programming"

There are two spaces in this string, so our program will print a string
"c programming". It will remove spaces when they occur more than one time consecutively in string anywhere.

C programming code

#include <stdio.h>
 
int main()
{
   char text[100], blank[100];
   int c = 0, d = 0;
 
   printf("Enter some text\n");
   gets(text);
 
   while (text[c] != '\0')
   {
      if (!(text[c] == ' ' && text[c+1] == ' ')) {
        blank[d] = text[c];
        d++;
      }
      c++;
   }
 
   blank[d] = '\0';
 
   printf("Text after removing blanks\n%s\n", blank);
 
   return 0;
}

C programming code using pointers

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define SPACE ' '
 
main()
{
   char string[100], *blank, *start;
   int length, c = 0, d = 0;
 
   printf("Enter a string\n");
   gets(string);
 
   length = strlen(string);
 
   blank = string;
 
   start = (char*)malloc(length+1);
 
   if ( start == NULL )
      exit(EXIT_FAILURE);
 
   while(*(blank+c))
   {
      if ( *(blank+c) == SPACE && *(blank+c+1) == SPACE )
      {}
      else
      {
         *(start+d) = *(blank+c);
  d++;
      }
      c++;
   }
   *(start+d)='\0';
 
   printf("%s\n", start);
 
   free(start);     
 
   return 0;
}

Compiler used: 

GCC

Output of program: 

Sort a string in c

c program to sort a string in alphabetic order

C program to sort a string in alphabetic order: For example if user will enter a string "programming" then output will be "aggimmnoprr" or output string will contain characters in alphabetical order.

C programming code

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
void sort_string(char*);
 
main()
{
   char string[100];
 
   printf("Enter some text\n");
   gets(string);
 
   sort_string(string);
   printf("%s\n", string);
 
   return 0;
}
 
void sort_string(char *s)
{
   int c, d = 0, length;
   char *pointer, *result, ch;
 
   length = strlen(s);
 
   result = (char*)malloc(length+1);
 
   pointer = s;
 
   for ( ch = 'a' ; ch <= 'z' ; ch++ )
   {
      for ( c = 0 ; c < length ; c++ )
      {
         if ( *pointer == ch )
         {
            *(result+d) = *pointer;
            d++;
         }
         pointer++;
      }
      pointer = s;
   }
   *(result+d) = '\0';
 
   strcpy(s, result);
   free(result);
}

Substring in c program

Substring in c programming, c substring

Substring in c programming: c programming code to find a substring from a given string and for all substrings of a string, For example substrings of string "the" are "t", "th", "the", "h", "he" and "e" to find substring we create our own c substring function which returns a pointer to string. String address, length of substring required and position from where to extract substring are the three arguments passed to function. String.h does not contain any library function to directly find substring.

C substring code

#include <stdio.h>
#include <malloc.h>
 
char* substring(char*, int, int);
 
main() 
{
   char string[100], *pointer;
   int position, length;
 
   printf("Enter a string\n");
   gets(string);
 
   printf("Enter the position and length of substring\n");
   scanf("%d%d",&position, &length);
 
   pointer = substring( string, position, length);
 
   printf("Required substring is \"%s\"\n", pointer);
 
   free(pointer);
 
   return 0;
}
 
/*C substring function: It returns a pointer to the substring */
 
char *substring(char *string, int position, int length) 
{
   char *pointer;
   int c;
 
   pointer = malloc(length+1);
 
   if (pointer == NULL)
   {
      printf("Unable to allocate memory.\n");
      exit(EXIT_FAILURE);
   }
 
   for (c = 0 ; c < position -1 ; c++) 
      string++; 
 
   for (c = 0 ; c < length ; c++)
   {
      *(pointer+c) = *string;      
      string++;   
   }
 
   *(pointer+c) = '\0';
 
   return pointer;
}

C substring program output:

C code for all substrings of a string

#include <stdio.h>
#include <string.h>
#include <malloc.h>
 
char* substring(char*, int, int);
 
main() 
{
   char string[100], *pointer;
   int position = 1, length = 1, temp, string_length;
 
   printf("Enter a string\n");
   gets(string);
 
   temp = string_length = strlen(string);
 
   printf("Substring of \"%s\" are\n", string);
 
   while (position <= string_length)
   {
      while (length <= temp)
      {
         pointer = substring(string, position, length);
         printf("%s\n", pointer);
         free(pointer);
         length++;
      }
      temp--;
      position++;
      length = 1;
   }
 
   return 0;
}
 
/* Use substring function given in above c program*/ 

Substring code output: