Day 4: Mastering Input/Output in ANSI C

Hello, C enthusiasts! ??Today, let’s dive into Input and Output (I/O) in ANSI C, a core concept that bridges the interaction between your program and the user. Whether you’re capturing input, printing output, or formatting data, mastering I/O is essential for building efficient and user-friendly applications. Let’s break it down!

1. Basic Input and Output in C

In C, the stdio.h library is used for all input and output operations. Two key functions you’ll often work with are:

• scanf(): Reads user input and stores it in a variable.

Example:

int num;
scanf("%d", &num); // Reads an integer value        

• printf(): Prints output to the console.

Example:

int num = 10;
printf("The number is: %d", num); // Prints an integer value        

Using these functions, you can handle basic types like integers, floats, and characters. For example:

#include <stdio.h>
int main() {
    int num;
    float f;
    char ch;

    printf("Enter an integer: ");
    scanf("%d", &num);
    printf("Entered integer is: %d\n", num);

    printf("Enter a float: ");
    scanf("%f", &f);
    printf("Entered float is: %.2f\n", f);

    printf("Enter a character: ");
    scanf(" %c", &ch); // Space before %c to handle newline
    printf("Entered character is: %c\n", ch);

    return 0;
}        

Output Example:

Enter an integer: 10  
Entered integer is: 10  

Enter a float: 3.14  
Entered float is: 3.14  

Enter a character: A  
Entered character is: A          

2. Format Specifiers in C

Format specifiers tell the compiler how to interpret input or output data. Here’s a quick rundown of some common ones:

• %d: Signed integer (e.g., int)
• %f: Float values (e.g., float)
• %c: Single characters (e.g., char)
• %s: Strings (e.g., arrays of characters)
• %p: Memory address (e.g., pointers)

Example of Use:

#include <stdio.h>
int main() {
    int num = 42;
    float pi = 3.14;
    char letter = 'A';

    printf("Integer: %d\n", num);
    printf("Float: %.2f\n", pi);
    printf("Character: %c\n", letter);

    return 0;
}        

3. Strings and Scansets in C

Handling strings? C provides special format specifiers for these, which are used %s to read and print strings. For more control, scansets let you read input until a specific condition is met.

Example:

#include <stdio.h>
int main() {
    char name[50];
    char sentence[100];

    printf("Enter your name: ");
    scanf("%s", name);
    printf("Hello, %s!\n", name);

    printf("Enter a sentence: ");
    scanf(" %[^\n]s", sentence); // Reads until a newline
    printf("You said: %s\n", sentence);

    return 0;
}        

Output Example:

Enter your name: John  
Hello, John!  

Enter a sentence: Hello World!  
You said: Hello World!          

4. Input/Output Formatting in C

You can customize how input and output are displayed by using field width, alignment, and precision.

Example:

#include <stdio.h>
int main() {
    char str[] = "CProgramming";
    printf("%20s\n", str);   // Right-aligned within 20 spaces
    printf("%-20s\n", str);  // Left-aligned within 20 spaces
    printf("%.5s\n", str);   // Prints only the first 5 characters

    return 0;
}        

Output:

       CProgramming  
CProgramming         
CProg          

?? Takeaway

Mastering I/O operations in C is crucial for creating interactive programs. With scanf, printf, and format specifiers, you can handle input/output for simple and complex data types.

?? Your turn! What’s your favourite trick or best practice when working with I/O in C? Drop your tips in the comments below!