Give the count a name

A ticket counter needs to remember its count. int seats = 8; gives that count a name: int is the type, seats the name, and 8 the initial value. C checks types as it processes your program.

To print a value, match its placeholder to its type: %d for int, %f for double, and %c for char. %.1f asks for one digit after the decimal point. Arguments after the format string must appear in placeholder order. A char is one character in single quotes; double quotes mark a string.

Run the ticket count, then look at what the second assignment changes:

#include <stdio.h>

int main(void) {
    int tickets = 3;
    printf("Tickets: %d\n", tickets);
    tickets = tickets + 2;
    printf("Tickets now: %d\n", tickets);
    return 0;
}

The second assignment replaces the value, not its type. The next program prints a character and a fractional distance:

#include <stdio.h>

int main(void) {
    double distance = 2.5;
    char zone = 'B';
    printf("Zone %c is %.1f km away\n", zone, distance);
    return 0;
}

Change distance to 3.75 and %.1f to %.2f. Check how many decimal places print.

A value before a read

int seats = 8; both declares and initializes seats. In seats = seats + 1;, C computes the right side first, then stores the new value; = is assignment, not an equation. Never read an uninitialized local variable. Integer 8 and floating-point 8.0 have different types, and using the wrong printf conversion is unsafe. Use integers for counts, floating-point values when fractions matter, and %% to print a literal percent sign.