Width, Precision, Flags
Control formatting.
Width, Precision, Flags is a free C Academy lesson on CoddyKit — 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, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
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.
Recap: Width, Precision, Flags
You learned to format output precisely.
- A width number sets minimum field size
-left-aligns,0zero-pads.Nsets decimal precision for floats and length for strings+and space control the sign*supplies width at runtime
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, and the C Academy course includes 4 lessons in total. 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.
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; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
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.
All lessons in this course
- printf Format Specifiers
- scanf and Input
- Width, Precision, Flags
- Common I/O Pitfalls