C Academy · Lesson

printf Format Specifiers

Print values precisely.

Lesson 1 of 413 steps

printf Format Specifiers is a free C Academy lesson on CoddyKit. This is lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C Academy learning path, and your progress syncs across the web and the CoddyKit app. The C Academy course includes 4 lessons in total.

What printf Does

printf writes formatted text to the screen. Format specifiers starting with % are replaced by your values.

#include <stdio.h>
int main(void) {
    printf("Hello, world!\n");
    return 0;
}

Printing Integers with %d

Use %d for a signed decimal integer.

#include <stdio.h>
int main(void) {
    int age = 30;
    printf("Age: %d\n", age);
    return 0;
}

Printing Floats with %f

Use %f for floating-point values. By default it prints six decimals.

#include <stdio.h>
int main(void) {
    double price = 9.5;
    printf("Price: %f\n", price);
    return 0;
}

Printing Characters with %c

Use %c to print a single character.

#include <stdio.h>
int main(void) {
    char grade = 'A';
    printf("Grade: %c\n", grade);
    return 0;
}

Printing Strings with %s

Use %s to print a C string (a char array).

#include <stdio.h>
int main(void) {
    char name[] = "Alice";
    printf("Name: %s\n", name);
    return 0;
}

Multiple Values

One printf can hold several specifiers; supply the arguments in the same order.

#include <stdio.h>
int main(void) {
    char name[] = "Bob";
    int age = 25;
    printf("%s is %d years old\n", name, age);
    return 0;
}

Printing a Literal Percent

To print an actual % sign, write %%.

#include <stdio.h>
int main(void) {
    int pct = 80;
    printf("Battery: %d%%\n", pct);
    return 0;
}

Hexadecimal and Octal

%x prints in hexadecimal and %o in octal.

#include <stdio.h>
int main(void) {
    int n = 255;
    printf("hex: %x  oct: %o\n", n, n);
    return 0;
}

Long and Unsigned

Use %ld for long and %u for unsigned int to match the argument type.

#include <stdio.h>
int main(void) {
    long big = 1000000L;
    unsigned int u = 4000000000u;
    printf("%ld  %u\n", big, u);
    return 0;
}

Matching Type to Specifier

The specifier must match the argument type. A mismatch like printing a double with %d is undefined behavior.

#include <stdio.h>
int main(void) {
    double d = 3.5;
    printf("%f\n", d);
    return 0;
}

Newlines and Tabs

Escape sequences like \n and \t control layout inside the format string.

#include <stdio.h>
int main(void) {
    printf("Col1\tCol2\n");
    printf("a\tb\n");
    return 0;
}

Quick Check

Test your understanding of printf specifiers.

Answer it in the interactive lesson

Recap: printf Format Specifiers

You learned how printf formats output.

%d integers, %f floats, %c chars, %s strings
%x hex, %o octal, %u unsigned, %ld long
%% prints a literal percent
Specifier must match argument type
Escape sequences control layout

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Frequently Asked Questions

Is the “printf Format Specifiers” lesson free?

Yes — the full text of “printf Format Specifiers” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C Academy course, upgrade to CoddyKit PRO. The C Academy course includes 4 lessons in total.

What will I learn in “printf Format Specifiers”?

Print values precisely. You practise C Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start C Academy?

No prior experience is required. C Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 4.

How long does the “printf Format Specifiers” lesson take?

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