Learn how to display output on the screen using printf()
What is this topic?
This guide explains C Output - Display Text and Values in simple terms, what it does, and how to use it in real C programs.
Why We Need It
- It helps you write correct and reliable C code.
- It makes your programs easier to read and maintain.
- It is used in real projects and interviews.
- It reduces common beginner mistakes.
- It builds a strong foundation for advanced topics.
Use Cases
- Building practical C programs step by step.
- Solving real coding tasks with clean logic.
- Preparing for exams, interviews, and projects.
- Understanding and improving existing C code.
What is Output?
Output is information your program sends to the screen. The most common way to create output in C is using the printf() function.
Simple Output Example
#include <stdio.h>
int main() {
printf("Hello, World!");
return 0;
}
Output:
Hello, World!
The printf() Function
printf() stands for “print formatted” and displays text on the screen.
Basic Syntax
printf("text to display");
Examples
Example 1: Simple Text
#include <stdio.h>
int main() {
printf("I am learning C!");
return 0;
}
Output:
I am learning C!
Example 2: Multiple printf Statements
#include <stdio.h>
int main() {
printf("First line");
printf("Second line");
return 0;
}
Output:
First lineSecond line
Notice how they printed on the same line? We need to add a newline!
Newlines: \n
The \n character creates a new line.
#include <stdio.h>
int main() {
printf("First line\n");
printf("Second line\n");
return 0;
}
Output:
First line
Second line
More Escape Sequences
| Sequence | Effect |
|---|---|
\n |
New line |
\t |
Tab (space) |
\\ |
Backslash |
\" |
Double quote |
\' |
Single quote |
Printing Numbers and Variables
Use format specifiers to print numbers:
Format Specifiers
| Specifier | Data Type | Example |
|---|---|---|
%d |
Integer | printf("%d", 42); |
%f |
Float (decimal) | printf("%f", 3.14); |
%c |
Character | printf("%c", 'A'); |
%s |
String | printf("%s", "text"); |
Example: Printing an Integer
#include <stdio.h>
int main() {
int age = 25;
printf("I am %d years old\n", age);
return 0;
}
Output:
I am 25 years old
Example: Printing a Float
#include <stdio.h>
int main() {
float price = 19.99;
printf("Price: $%f\n", price);
return 0;
}
Output:
Price: $19.990000
Notice the extra zeros! To fix this, use %.2f:
printf("Price: $%.2f\n", price); // Shows 2 decimal places
Output:
Price: $19.99
Practical Examples
Example 1: Personal Information
#include <stdio.h>
int main() {
char name[] = "John";
int age = 25;
float height = 5.9;
printf("Name: %s\n", name);
printf("Age: %d\n", age);
printf("Height: %.1f\n", height);
return 0;
}
Output:
Name: John
Age: 25
Height: 5.9
Example 2: Simple Math Results
#include <stdio.h>
int main() {
int result = 10 + 5;
printf("10 + 5 = %d\n", result);
float division = 15.0 / 4.0;
printf("15 / 4 = %.2f\n", division);
return 0;
}
Output:
10 + 5 = 15
15 / 4 = 3.75
Multiple Values
Print multiple values with one printf:
#include <stdio.h>
int main() {
int x = 10;
int y = 20;
printf("x = %d, y = %d\n", x, y);
return 0;
}
Output:
x = 10, y = 20
Common Mistakes
Mistake 1: Forgetting the Newline
printf("Line 1");
printf("Line 2"); // Prints on same line
Fix:
printf("Line 1\n");
printf("Line 2\n");
Mistake 2: Wrong Format Specifier
int age = 25;
printf("Age: %f\n", age); // ✗ %f is for floats, not ints
Fix:
printf("Age: %d\n", age); // ✓ %d is for integers
Mistake 3: Missing Variable
printf("My number: %d\n"); // ✗ No value provided
Fix:
printf("My number: %d\n", 42); // ✓ Value provided
Quick Reference: Format Specifiers
printf("%d", integer); // Integer
printf("%.2f", decimal); // Decimal (2 places)
printf("%c", character); // Single character
printf("%s", string); // String of text
Practice Exercise
Create a file called output.c:
#include <stdio.h>
int main() {
printf("=== Welcome ===\n");
printf("My name is John\n");
printf("I love programming!\n");
int score = 95;
float grade = 4.0;
printf("\nScore: %d\n", score);
printf("Grade: %.1f\n", grade);
return 0;
}
Compile and run:
gcc output.c -o output
./output
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