Input and Output

Introduction

Console I/O lives in stdio.h: formatted output with printf and formatted input with scanf. For line-based text, fgets is often safer than unbounded scanf.

Understanding the topic

printf Formatted output — printf("format", args);

scanf Formatted input — always pass address with & for variables.

Safer input Prefer fgets for strings to avoid buffer overflow.

• printf — Formatted output — printf("format", args);.
• scanf — Formatted input — always pass address with & for variables.
• Safer input — Prefer fgets for strings to avoid buffer overflow.

Step-by-step explanation

1. printf — Formatted output — printf("format", args);.
2. scanf — Formatted input — always pass address with & for variables.
3. Safer input — Prefer fgets for strings to avoid buffer overflow.

Syntax reference

Syntax reference:

printf("format", args);
scanf("format", &var);

Informative example

Example program:

#include <stdio.h>

int main(void) {
    int n;
    printf("Enter a number: ");
    scanf("%d", &n);
    printf("You entered: %d\n", n);
    return 0;
}

Execution workflow

Best practices

• Enable warnings: gcc -Wall -Wextra -std=c11 source.c -o app
• Give every variable a defined value before it is read.
• Stay inside array bounds — C will not stop you from over-running a buffer.

Common mistakes

• Never use scanf("%s") without width limit on fixed buffers

Hands-on exercise

Practice problems:

• Read and print an integer
• Read a full line with fgets

Summary

Input and Output in C — Formatted console I/O with stdio and safer line-reading patterns.