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kbhit() in C

In this article, we will discuss the kbhit() function in C with its example, advantages, and disadvantages.

kbhit() function does not exist in the C standard library. Although, it is frequently used on Windows systems to check whether a keyboard key has been depressed. You can use a program to see if a key is waiting to be read in the keyboard buffer without preventing the program from running. This function is frequently applied to interactive console-based programs or games that demand immediate user input without waiting for the user to press the Enter key.

As kbhit() function is not a part of the default C library, not all platforms might support it. Platform-specific methods for managing input events or libraries like ncurses can be used if cross-platform keyboard input is required.

The kbhit() function determines if a key has been depressed or not. You must include the conio.h header file to utilize the 'kbhit' function. When a key is depressed, a value is 1 returned; otherwise, zero is returned.


Let's take a program to understand the use of kbhit() function in C.


Enter key ESC to exit
You have entered: i
You have entered: P
You have entered: S
You have entered: w
You have entered: 7
You have entered: /
You have entered: *
You have entered: +


  • #include <stdio.h>: This line contains the standard input/output (stdio) header file, which offers functions for input and output operations like printf.
  • #include <conio.h>: This line includes the h header file, which is not a standard C library header. It is specific to Windows and provides functions like kbhit() and fetch() for handling keyboard input without waiting for the Enter key.
  • It is exclusive to Windows and offers fetch() and kbhit() routines for handling keyboard input without waiting for the Enter key.
  • int main()...: Any C program's main function is its entry point. It is where the program's execution starts.
  • char ch;: This line declares the char type variable ch, which will be used to hold the user input (a single character).
  • Using the printf() function, the line printf("Enter key ESC to exit"); prints the message "Enter key ESC to exit" on the screen. The user can press the ESC key to end the program or enter any key to proceed.
  • while (1) ...: As the condition is 1, which is always authentic, this while loop never ends (runs forever). The loop will stop once it comes across a break statement.
  • If (kbhit()): Using the kbhit() function from h, this line checks for critical presses within the loop. If a key is pressed and ready to be read from the keyboard buffer, the kbhit() function returns a non-zero result (accurate).
  • Ch = getch();: If a key's pressed (i.e., kbhit() returns genuine), this line reads the individual from the keyboard buffer using the getch() function. The fetch() function does not watch for the Enter key to be pressed; it directly reads the key pressed and returns the ASCII value of the user.
  • If the character ch equals the ASCII value (27) of the ESC key, the line will break. In many programs, the ESC key is frequently used as the exit key. If the user pushes the ESC key, the program will leave the loop and utilize the break statement to end, making the condition accurate.
  • printf ("You have entered: %c," "ch"): This line will run even if the user didn't use the ESC key (i.e., if the loop wasn't broken). The user-inputted character (stored in ch) and the phrase "You have entered:" are printed using the printf() function.
  • Return 0; This line marks the end of the main() function and causes the program to return the value 0 after the while loop. The operating system typically reports a return result of 0 as successful program execution.
  • Keep in mind that the h header is unique to Windows and is not a component of the standard C library. If you intend to write cross-platform programs, consider using libraries like ncurses to handle keyboard input in a platform-independent manner.

Complexity Analysis:

The C program offers simple-to-understand time complexity and relatively low space complexity.

Time Complexity:

  • The printf("Enter key ESC to exit") statement has an O(1) time complexity because it just performs a single and simple output operation.
  • When the ESC key (ASCII value 27) is hit, the while (1) loop begins to run forever and ends with the break statement. The loop's time complexity is seen as O(1) because there are no operations inside that scale with the input size.
  • The program's overall time complexity is O(1) due to the infinite loop's inability to conduct any operations that scale with the size of the input.

Space Complexity:

  • The statement char ch; declares a single char-type variable named ch that uses a fixed amount of memory regardless of the input size. Therefore, this variable's space complexity is O(1).
  • As they don't depend on the input size, the constant-size message strings supplied to the printf() function, such as "You have entered:" and "Enter key ESC to exit", likewise have an O(1) space complexity.
  • The fetch() and kbhit() procedures from h need some internal memory to manage the keyboard buffer and status. However, this memory usage is constant and does not increase with the amount of input, giving these functions an O(1) space complexity.
  • As all declared variables and function calls have fixed memory requirements that do not change with the input size, the program's overall space complexity is O(1).


There are various advantages of the kbhit() function in C. Some main advantages of the kbhit() function in C are as follows:

Non-blocking keyboard enters: One of the main advantages of the kbhit() function is that it lets you check for keyboard entries without blocking off this system's execution. Unlike other input features like scanf() and getchar(), kbhit() returns quick results, although no key is pressed, making it suitable for real-time enter managing in interactive console-based programs and games.

Real-time response: The kbhit() function can assist in reaping actual-time interactivity for video games or applications that require non-stop person entry or brief responses to keyboard occasions. Since it does not watch for the consumer to press the Enter key, the program can respond immediately to critical presses.

No need for Enter key: With kbhit(), you don't need the user to press the Enter key after typing a character. This behaviour is beneficial for certain types of applications, such as games, where waiting for the Enter key might disrupt the user experience.

Single-individual input: The kbhit() function is beneficial for analyzing single-character inputs, which are frequent enough for many interactive console programs. It can simplify the entry processing with good judgment, as you best address one individual at a time.

Simple implementation: The kbhit() feature is straightforward, and the code for the keyboard entry with kbhit() function is concise and straightforward.


There are various disadvantages of the kbhit() function in C. Some main disadvantages of the kbhit() function in C are as follows:

Limited input processing: The kbhit() function only looks for one character in the keyboard buffer. Kbhit() won't recognize all the keys tapped simultaneously or quickly after one another. It might not be adequate for some applications that call for intricate or multiple vital combinations because it can only read one character at a time.

No key release detection: Key release cannot be detected using the kbhit() function, which only detects vital presses. You cannot immediately recognize and react to crucial release occurrences because of this restriction. It would help if you employed more advanced strategies involving additional state tracking to manage significant press and release events.

Platform-precise: The kbhit() function is not a trendy C function and is particular to specific environments, including Windows and some DOS environments. It is unavailable on Unix-primarily based structures (e.g., Linux, macOS) or other running systems.

Lack of buffering: When a function is called, kbhit() just looks to see if a key has actually been depressed. Additional logic is needed if you want to process or buffer multiple characters in the order they were typed.

Limited entry dealing: The kbhit() function might be needed for more complicated input dealing with multi-key combinations. In such instances, you should consider different input libraries or gadget-particular methods.

Because of these restrictions, kbhit() function may not be appropriate for applications requiring more sophisticated keyboard input handling, such as those in gaming, GUIs, or those with intricate control schemes. In such cases, using specialized input libraries like ncurses, platform-specific techniques, or even game development frameworks that offer extensive input-handling features is preferable. These alternatives may provide better control, flexibility, and portability across many systems.

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