C Academy · Lesson

Width, Precision, Flags

Control formatting.

Lesson 3 of 413 steps

Width, Precision, Flags is a free C Academy lesson on CoddyKit. This is lesson 3 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.

Controlling Output Width

A number after % sets the minimum field width. The value is right-aligned and padded with spaces.

#include <stdio.h>
int main(void) {
    printf("[%5d]\n", 42);
    return 0;
}

Left Alignment

A - flag left-aligns the value within the field.

#include <stdio.h>
int main(void) {
    printf("[%-5d]\n", 42);
    return 0;
}

Zero Padding

A 0 flag pads numbers with leading zeros instead of spaces.

#include <stdio.h>
int main(void) {
    printf("[%05d]\n", 42);
    return 0;
}

Precision for Floats

.N sets how many digits appear after the decimal point.

#include <stdio.h>
int main(void) {
    printf("%.2f\n", 3.14159);
    return 0;
}

Width and Precision Together

Combine them as %width.precisionf for aligned decimal columns.

#include <stdio.h>
int main(void) {
    printf("[%8.2f]\n", 3.14159);
    return 0;
}

Precision for Strings

With %s, precision limits how many characters are printed.

#include <stdio.h>
int main(void) {
    printf("[%.3s]\n", "Hello");
    return 0;
}

The Plus Flag

The + flag forces a sign to appear even for positive numbers.

#include <stdio.h>
int main(void) {
    printf("%+d %+d\n", 7, -7);
    return 0;
}

Space Flag

A space flag prints a leading space for positive numbers, useful for alignment with negatives.

#include <stdio.h>
int main(void) {
    printf("% d\n% d\n", 7, -7);
    return 0;
}

Building a Table

Field widths line up columns neatly.

#include <stdio.h>
int main(void) {
    printf("%-10s%5d\n", "Apples", 12);
    printf("%-10s%5d\n", "Pears", 7);
    return 0;
}

Currency Formatting

Two decimals plus a width gives a clean money column.

#include <stdio.h>
int main(void) {
    printf("$%8.2f\n", 1234.5);
    printf("$%8.2f\n", 9.99);
    return 0;
}

Dynamic Width

An asterisk lets you pass the width as an argument at runtime.

#include <stdio.h>
int main(void) {
    int w = 6;
    printf("[%*d]\n", w, 42);
    return 0;
}

Quick Check

Test your understanding of width and precision.

Answer it in the interactive lesson

Recap: Width, Precision, Flags

You learned to format output precisely.

A width number sets minimum field size
- left-aligns, 0 zero-pads
.N sets decimal precision for floats and length for strings
+ and space control the sign
* supplies width at runtime

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Frequently Asked Questions

Is the “Width, Precision, Flags” lesson free?

Yes — the full text of “Width, Precision, Flags” 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 “Width, Precision, Flags”?

Control formatting. 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 3 of 4.

How long does the “Width, Precision, Flags” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this C Academy lesson?

Yes. Every C Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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