Printing with printf

printf prints exactly what you give it

It never adds a new line by itself: you write \n where you want one. \t jumps to the next tab stop, and \" prints a double quote.

To print a number, put %d in the text and the number after a comma: printf("%d\n", 7 + 3); prints 10.

Watch the output build up

#include <stdio.h>

int main() {
    printf("Score: ");
    printf("%d\n", 40 + 2);
    printf("7 + 3 = %d\n", 7 + 3);
    printf("She said \"hi\"\n");
    return 0;
}

1. Line 4: No \n, so the cursor stays at the end of this line.
2. Line 5: %d is replaced by the value after the comma: 40 + 2 is worked out to 42.
3. Line 6: Text inside the quotes is printed as it is; only %d is replaced.
4. Line 7: \" prints a quote without ending the text.

No new line?

#include <stdio.h>

int main() {
    printf("A");
    printf("B\n");
    printf("C\n");
    return 0;
}

What does this print?

• A B C
• AB C
• ABC

Two numbers in one line

#include <stdio.h>

int main() {
    printf("%d and %d\n", 2 * 5, 9 - 4);
    return 0;
}

What does this print?

• 10 and 5
• %d and %d
• 2 * 5 and 9 - 4

Exercise: Print a staircase

Print these three lines:

*

**

***

Exercise: A quoted ticket

Print exactly these two lines. The gap is a tab (\t) and the quotes are part of the output:

Seat "A12"

Fare 250

Let C work out the fare: print 200 + 50 with %d.