User Input scanf and getchar in C

Learn how to get user input in C using scanf and getchar on Debian 12 using Vim. Includes practical examples and clear explanations to understand both methods.

User Input in C: Using scanf and getchar

Getting input from users is a fundamental skill in C programming. It lets your program interact with users dynamically rather than using fixed data. Two commonly used functions for input are scanf() and getchar().

scanf() Function

scanf() reads formatted input from the standard input (keyboard). It is ideal for reading integers, floats, characters, and strings. Example:

int age;
scanf(\\"%d\\", &age);

Here, %d tells scanf() to read an integer, and &age passes the address of the variable to store the input.

getchar() Function

getchar() reads a single character from the user. Unlike scanf(), it is more low-level and does not require format specifiers.

char ch;
ch = getchar();

Complete Example

The following program demonstrates both scanf() and getchar() in action.

#include 

int main() 
    int age;
    char initial;

    printf(\\"Enter your age: \\");
    scanf(\\"%d\\", &age);

    while(getchar() != '\
'); // clear input buffer

    printf(\\"Enter the first letter of your name: \\");
    initial = getchar();

    printf(\\"You entered age %d and initial %c\\\
\\", age, initial);

    return 0;

Step-by-Step Explanation

• scanf(\\"%d\\", &age): Gets an integer from user input and stores it in age.
• getchar(): Captures the next typed character. We use it after a scanf to get another character without interference from leftover newlines.
• while(getchar() != '\ '): This loop clears the newline character from the input buffer so getchar works correctly.

Running the Program

Use the following commands in Debian 12 to compile and run:

gcc input.c -o input
./input

Expected Output

Enter your age: 25
Enter the first letter of your name: J
You entered age 25 and initial J

Conclusion

Understanding input functions like scanf and getchar is essential to write interactive programs. Practice using them in different ways to read various types of data effectively.

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