Dos.h Header File in C Language

• Dos.h is a header file in C. Interrupt handling, sound generation, date and time functions, and other tasks can be performed using the functions in this library.
• This is exclusive to Borland and can be used with compilers such as the Turbo C compiler. The following functions are supported by this library:

Delay():

• In C, the delay() function is used to temporarily stop the execution of a program.

// C program to implement delay()
#include <dos.h>
#include <stdio.h>
#include <stdlib.h>
// Driver Code
int main()
{
printf("Takes 10 sec and exit.\n");
    // Delay the program execution
    // for 1 second
delay(10000);
    return 0;
}

sleep():

• In C, the sleep() function is used to pause the execution of a program for a while parameters: Takes time in seconds to limit program execution to that time.
• The demo program sleep() looks like this:

// C program to implement sleep()
#include <dos.h>
#include <stdio.h>
#include <stdlib.h>
// Driver Code
int main()
{
printf("Wait 2 sec and exit.\n");


    // Delay the program execution
    // for by 2 seconds
sleep(2);
    return 0;
}

getdate():

• To get the current system date, C uses the getdate() function Parameters: Accepts a date structure defined in the dos.h library itself.
• The da_day(), da_mon() and da_year() functions are used to print the date The getdate() demo program looks like this:

// C program to implement getdate()
#include <dos.h>
#include <stdio.h>
#include <stdlib.h>
// Driver Code
int main()  {
    // Structure of date
    struct date a;
    getdate(&a);
    // Print the date, month and year
printf("The Date is: %d/%d/%d\n", a.da_day,
a.da_mon,
a.da_year);
    return 0; }

gettime():

• The C function get time()  is used to get the system time Parameters: Accepts the time structure defined in the dos.h library.
• The date is output with fnosound(): The souns() functions ti_hour(), ti_min() and ti_sec()  can be stopped with the C function nosound().
•  The get time() demo program looks like this:

// C program to implement gettime()
#include <dos.h>
#include <stdio.h>
#include <stdlib.h>
// Driver Code
int main()
{
    // Structure of time
    struct time t;
    // Function call to get the time
    // of the system
    getdate(&t);
    // Print the hour, minutes and second
printf("The time is: %d : %d : %d\n", x.ti_hour,
           x.ti_min,
           x.ti_sec);
    return 0;
}

Sound():

• In our system, the sound() function in C is used to play different sounds with different frequencies.
• Options: It detects the frequency and plays the corresponding tone in our system.
•  The sound demo() program looks like this:

// C program to implement sound()
#include <dos.h>
#include <stdio.h>
#include <stdlib.h>
// Driver Code
int main()
{
    // Initialise frequency
    int x = 200;
    // Loop for playing sound of
    // increasing frequency
    for (; x < 1000; x++) {
        // Function to play sound
        sound(x);
delay(25);
    } 
    // To stop the frequency
nosound();
    return 0;
}

No sound():

• The nosound() function in C is used to stop the sound played by the sounds() function.
• Parameters: No parameters are accepted.

#include <dos.h>
#include <stdio.h>
#include <stdlib.h>
// Driver Code
int main()
{
    // Initialise frequency
    int x = 200;
    // Function call to play sound
    // with frequency 200htz
    sound(x);
    // Delay sound for 1 sec
delay(1000);
    // To stop the sound
nosound();
    return 0;
}

Using Standard Header Files

• #include: Input and output operations are performed using the scanf() and printf() functions. #include: Use cin and court to act as input and output streams. #include: Used for various string manipulation functions such as strlen(), strcmp(), strcpy(), size().
• #include<math.h>: Used to perform math operations such as pow(), sqrt(), log2(). #include: Used to access the set() and set precision()  functions to limit the number of decimal places for variables.
•  #include: Used by signal handler functions such as raise() and signal().
• #include: Standard argument functions such as va_start() and va_arg() are executed here. It is also used to fetch arguments from a variable-length argument list within a program and to indicate the start of a variable-length argument list
•  #include: Errno, strerror, error, and other error handling functions rely on this. #include: Used to control what data  is written to the file and what data  is read from the file as  output
•  #include: Used to perform functionsrelated to date() and time() such as setdate() and getdate().
• They are also used to get the CPU time and change the system date re