C Variables, Data Types and I/O

In C, every variable must be declared with a type before use.

Type	Typical size	Format specifier	Example
char	1 byte	%c	`'A'`
int	4 bytes	%d	`25`
float	4 bytes	%f	`3.14f`
double	8 bytes	%lf	`3.14159`
long	8 bytes*	%ld	`100000L`
char[] (string)	n bytes	%s	`"hello"`

*Sizes depend on the compiler and platform. Use sizeof to check.

Input with scanf

#include <stdio.h>

int main() {
    int age;
    float height;
    char name[30];

    printf("Enter name, age and height: ");
    scanf("%s %d %f", name, &age, &height);   // & gives the address

    printf("%s is %d years old and %.1f cm tall\n", name, age, height);
    printf("sizeof(int) = %zu bytes\n", sizeof(int));
    return 0;
}

Enter name, age and height: Asha 20 162.5 Asha is 20 years old and 162.5 cm tall sizeof(int) = 4 bytes

Why no & for name?An array name already decays to the address of its first element.

Constants

#define PI 3.14159        // macro constant (preprocessor)
const int MAX = 100;      // typed constant

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