Functions

Write business rules with functions and conditional logic.

The print_book function

To avoid printing books repeatedly, you define a print_book function. This keeps the code organized and free of repetition.

void print_book(struct Book b) {
    printf("%s %d\n", b.title, b.year);
}

This function takes a struct Book and prints its title and year. The void return type means it returns no value. The function can be called anywhere in the catalog; this prevents code duplication.

Function call

You call the print_book function you defined inside main. The call uses the function name and the argument in parentheses.

struct Book b = {"Suç ve Ceza", 1866};
print_book(b);
// "Suç ve Ceza 1866"

Here b is passed by copying into the function; the function works on its own copy. This is pass by value. For large structs using a pointer may be more efficient; but for now pass by value is enough.

Exercise Define and call print_book

Define void print_book(struct Book b); inside it print b.title and b.year with printf. In main call print_book(b).

Show example solution

void print_book(struct Book b) {
    printf("%s %d\n", b.title, b.year);
}
print_book(b);

Test yourself

Match piece to task

void

Returns no value
struct Book b

Parameter
b.title

Member access
printf

Produces output
What is the return type of the print_book function?
- int
- void
- char *
- struct Book
Show answer

void — print_book returns no value; its return type is void.

Fill in the blank: function definition

____ print_book(struct Book b) {
    printf("%s %d\n", b.title, b.year);
}

Show answer

void print_book(struct Book b) {
    printf("%s %d\n", b.title, b.year);
}

Next lesson: Memory management

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