The conio.h header file is a C library that provides functions for console input and output in the DOS and Windows environments. “Conio” stands for “console input/output”. This header file is not part of the standard C library and is specific to DOS and Windows systems.

Some commonly used functions declared in conio.h include:

1. clrscr(): Clears the screen.
2. getch(): Reads a character directly from the console without echoing it.
3. getche(): Reads a character directly from the console and echoes it.
4. cprintf(): Prints formatted output to the console.
5. cscanf(): Reads formatted input from the console.

It’s important to note that conio.h is not standard and is not portable across different platforms or compilers. It was widely used in older DOS-based C programming, but it’s generally not recommended for modern development due to its lack of portability and non-standard nature. Most modern compilers, especially those targeting Unix-like systems, do not support conio.h. Instead, developers typically use standard input/output functions from stdio.h for console I/O.

getch()

The getch() function in conio.h reads a single character from keyboard. It doesn’t uses any buffer, so entered data is not displayed on the output screen.

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• ctype means characters type.
• Use of this functions is know which type of characters isdigit(), isalpha() , isupper(), islower()  , spunct().

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The windows.h header file is a fundamental header file for the Microsoft Windows operating system. It includes declarations for a wide range of functions and data types used in Windows programming. Here’s a basic example demonstrating the usage of windows.h for creating a simple Windows GUI application:

C Library – windows.h File

#include <windows.h>

// Function prototype for the window procedure
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);

int main() {
    // Get the handle to the instance of this application
    HINSTANCE hInstance = GetModuleHandle(NULL);

    // Create the main window
    HWND hwnd = CreateWindowEx(
        0,                              // Optional window styles
        L"WindowClass",                 // Window class
        L"My First Window",             // Window title
        WS_OVERLAPPEDWINDOW,            // Window style

        // Size and position
        CW_USEDEFAULT, CW_USEDEFAULT, 800, 600,

        NULL,       // Parent window    
        NULL,       // Menu
        hInstance,  // Instance handle
        NULL        // Additional application data
    );

    // Display the window
    ShowWindow(hwnd, SW_SHOWNORMAL);

    // Enter the message loop
    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}

// The window procedure
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
    switch (uMsg) {
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
        default:
            return DefWindowProc(hwnd, uMsg, wParam, lParam);
    }
    return 0;
}

This above example creates a simple window using the Windows API. The WindowProc function is the window procedure, which handles messages for the main window. The CreateWindowEx function creates the main window, and the ShowWindow function displays it. The program then enters a message loop (while (GetMessage...)) where it waits for and processes messages until the user closes the window.

Remember that this is just a basic example, and real-world Windows applications will involve more complexities and considerations. Additionally, GUI programming in Windows often involves using additional libraries, such as MFC (Microsoft Foundation Classes) or newer frameworks like WinUI.

Predefined functions of C Library – windows.h

The windows.h header in Windows programming provides declarations for various functions, data types, and constants used in Windows API. Here are some commonly used predefined functions available in windows.h:

C Library – windows.h predefined functions List

Function Category	Function	Note
Window Management Functions:	CreateWindowEx()	Creates an extended window.
	ShowWindow()	Sets the specified window’s show state.
	UpdateWindow()	Updates the client area of the specified window.
	DestroyWindow()	Destroys the specified window.
	DefWindowProc()	The default window procedure for window messages not processed by your window procedure.
Message Handling Functions:	GetMessage()	Retrieves a message from the calling thread’s message queue.
	TranslateMessage()	Translates virtual-key messages into character messages.
	DispatchMessage()	Dispatches a message to a window procedure.
	PostQuitMessage()	Posts a quit message to the message queue.
Thread Functions:	CreateThread()	Creates a new thread for parallel execution.
	GetCurrentThreadId()	Retrieves the thread identifier of the calling thread.
Synchronization Functions:	CreateMutex()	Creates or opens a named or unnamed mutex object.
	CreateEvent()	Creates or opens a named or unnamed event object.
	WaitForSingleObject()	Waits until the specified object is in the signaled state.
	ReleaseMutex()	Releases ownership of the specified mutex object.
File and File I/O Functions:	CreateFile()	Creates or opens a file or I/O device.
	ReadFile, WriteFile()	Reads from or writes to a file or I/O device.
	CloseHandle()	Closes an open object handle.
Memory Management Functions:	VirtualAlloc()	Reserves or commits a region of memory within the virtual address space of a specified process.
	VirtualFree()	Releases, decommits, or releases and decommits a region of memory.
Time Functions:	GetSystemTime()	Retrieves the current system date and time.
	Sleep()	Suspends the execution of the current thread for a specified interval.
Miscellaneous Functions:	MessageBox()	Displays a modal dialog box that contains a system icon, a set of buttons, and a brief application-specific message.
	GetLastError()	Retrieves the calling thread’s last-error code value.
	LoadLibrary, GetProcAddress()	Loads a dynamic-link library (DLL) into the calling process’s address space.

Note

These are just a few examples, and there are many more functions provided by Windows.h for various purposes. When working with Windows programming, documentation is an essential resource to understand and use these functions effectively. The next section only discussed Sleep() function.

sleep() in C Library – windows.h

if you have the following questions like

• How to use the delay function in C?
• How to use the C program delay function in Windows?

Here is your solution,

If you wanna use the delay feature, you can use the Sleep() function in the Windows platform, based on the compiler the Sleep() will call in different library files(Some times Sleep function will be winbase.h, Sometimes different). Don’t worry about that, if you include the windows.h the header file, that will be taken care of. why because everything all the sleep function necessary headers are already included in windows.h the file.

• Rule-1: You should add the header file #include <windows.h>
• Rule-2: Sleep() function first letter always Uppercase, if you declare in the small case the compiler might generate error “Undefined reference to sleep”.
• Rule-3: Sleep() function argument (Milliseconds) should be unsigned long type. If your call [Example : Sleep("ArunEworld")] Sleep() function with char type or other types, the compiler will generate an Error.

Please note that the sleep function may not be very precise, and the actual delay could be slightly longer due to system-related factors. If you need more precise timing, you might want to explore other methods or libraries for that purpose.

Sleep() Example-1

Code

#include <stdio.h>
#include <unistd.h>  // for sleep function

int main() {
    printf("ArunEworld: This is before the delay.\n");

    // Sleep for 3 seconds
    sleep(3);

    printf("ArunEworld: This is after the delay.\n");

    return 0;
}

Explanation

In this above example, the program will print the first message, then pause for 3 seconds using sleep(3), and finally print the second message after the delay.

Remember to include the <unistd.h> header for the sleep function to work.

Sleep() Example-2

The below code will be printed ArunEworld website every 1 second

#include <stdio.h>
#include <Windows.h>
int main() 
{
	while(1)
	{
		//print the aruneworld website address
		printf("www.ArunEworld.com.\r\n");
		
		//make a delay every in millisecond
		Sleep(1000);
	}
	
	return 0; 
}

Slep() Example-3

#include <stdio.h>
#include <Windows.h>
int main() 
{
	while(1)
	{
		//print the aruneworld website address
		printf("www.ArunEworld.com.\r\n");
		
		//make a delay every in millisecond
		Sleep("ArunEworld");
	}
	
	return 0; 
}

The above code will show the Error like "[Note] expected 'DWORD' but argument is of type 'char *'". Why because Sleep() the argument should be unsigned long. here ‘ArunEworld' is a charter pointer.

Refer to the C Examples – Time Delay

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