User Input with scanf

#include <stdio.h>

int main(void) {
    int age;
    printf("Enter your age: ");
    scanf("%d", &age);
    printf("In 5 years you will be %d.\n", age + 5);
    return 0;
}

Enter your age: 21
In 5 years you will be 26.

#include <stdio.h>

int main(void) {
    int a, b;
    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);
    printf("Sum = %d, Difference = %d, Product = %d\n", a + b, a - b, a * b);
    printf("Quotient = %.2f\n", (float)a / b);
    return 0;
}

Enter two numbers: 12 7
Sum = 19, Difference = 5, Product = 84
Quotient = 1.71

#include <stdio.h>

int main(void) {
    double weight, height;
    printf("Weight in kg: ");
    scanf("%lf", &weight);
    printf("Height in m: ");
    scanf("%lf", &height);
    printf("Your BMI is %.1f\n", weight / (height * height));
    return 0;
}

Weight in kg: 72.5
Height in m: 1.68
Your BMI is 25.7

#include <stdio.h>

int main(void) {
    int qty;
    char confirm;
    printf("Quantity: ");
    scanf("%d", &qty);
    printf("Confirm order? (Y/N): ");
    scanf(" %c", &confirm);      // the space skips the newline left by the Enter key
    printf("You ordered %d and answered %c\n", qty, confirm);
    return 0;
}

Quantity: 3
Confirm order? (Y/N): Y
You ordered 3 and answered Y

#include <stdio.h>
#include <string.h>

int main(void) {
    char first[20], city[50];
    printf("First name: ");
    scanf("%19s", first);                 // no & for arrays; 19 leaves room for '\0'
    getchar();                            // eat the newline left behind
    printf("City and state: ");
    fgets(city, sizeof city, stdin);      // reads spaces too
    city[strcspn(city, "\n")] = '\0';     // remove the trailing newline
    printf("%s lives in %s.\n", first, city);
    return 0;
}

First name: Asha
City and state: Bengaluru, Karnataka
Asha lives in Bengaluru, Karnataka.

#include <stdio.h>

int main(void) {
    int n;
    printf("Enter a number: ");
    if (scanf("%d", &n) == 1)
        printf("You typed %d\n", n);
    else
        printf("That was not a number!\n");
    return 0;
}

Enter a number: abc
That was not a number!