Format specifiers are used together with the printf() function to tell the compiler what type of data the variable is storing. It is basically a placeholder for the variable value.
A format specifier starts with a percentage sign %, followed by a character.
For example, to output the value of an int variable, you must use the format specifier %d or %i surrounded by double quotes, inside the printf() function:
#include<stdio.h>
int main() {
int myNum = 15;
printf("%d", myNum);
return 0;
}
To print other types, use %c for char and %f for float:
#include<stdio.h>
int main() {
// Create variables
int myNum = 5; // Integer (whole number)
float myFloatNum = 5.99; // Floating point number
char myLetter = 'D'; // Character
// Print variables
printf("%d\n", myNum);
printf("%f\n", myFloatNum);
printf("%c\n", myLetter);
return 0;
}
To combine both text and a variable, separate them with a comma inside the printf() function:
#include <stdio.h>
int main() {
int myNum = 5;
printf("My favorite number is: %d", myNum);
return 0;
}
To print different types in a single printf() function, you can use the following:
#include<stdio.h>
int main() {
int myNum = 5;
char myLetter = 'D';
printf("My number is %d and my letter is %c", myNum, myLetter);
return 0;
}
To add a variable to another variable, you can use the + operator:
#include<stdio.h>
int main() {
int x = 5;
int y = 6;
int sum = x + y;
printf("%d", sum);
return 0;
}
To declare more than one variable of the same type, use a comma-separated list:
#include<stdio.h>
int main() {
int x = 5, y = 6, z = 50;
printf("%d", x + y + z);
return 0;
}
You can also assign the same value to multiple variables of the same type:
#include<stdio.h>
int main() {
int x, y, z;
x = y = z = 50;
printf("%d", x + y + z);
return 0;
}
All C variables must be identified with unique names.
These unique names are called identifiers.
Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).
Note: It is recommended to use descriptive names in order to create understandable and maintainable code:
// Good
int minutesPerHour = 60;
// OK, but not so easy to understand what m actually is
int m = 60;
The general rules for naming variables are: