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Geekpedia » C Tutorials » Using the printf() function

Using the printf() function

A guide to the famous printf() function in C. Shows you how to output data in several ways. The tutorial is not yet complete but will be continued soon.

On Saturday, April 23rd 2005 at 10:48 AM

By Andrew Pociu (View Profile)

(Rated 4.5 with 15 votes)

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One of the most popular functions in C is the printf() function.

If you don't know what printf() does, compile the following code in a C file:

#include

void main(void)

{

printf("Hello World");

}

...and you will get:

Hello World

It's the easiest way to ouput information to the console. But printf() doesn't know just that, let's see what else printf() is capable of doing.

Outputting the value of a variable

We have a variable named myNum that stores the number 69. We want to output the value of this variable using the printf() function:

#include

void main(void)

{

int MyNum = 69;

printf("Outputting number %d", MyNum);

}

Because our variable is of type int we use %d to output its value where we want in the string. The result is:

Outputting number 69

With printf() you can also output the number in a hexadecimal form:

#include

void main(void)

{

int MyNum = 169;

printf("Number %d in hexadecimal format is %x", MyNum, MyNum);

}

The result being:

Number 169 in hexadecimal format is a9

Instead of %x you can use %X to get the result in uppercase (A9).

To get the number in octal format use %o as in the following example:

#include

void main(void)

{

int MyNum = 169;

printf("Number %d in octal format is %o", MyNum, MyNum);

}

And with the result:

Number 169 in octal format is 251

Moving on, let's see how we can output the character represented by an ASCII value. For example the ASCII value 65 outputted as a character gives the letter A. 66 is B, 67 is C and so on.

#include

void main(void)

{

int MyChar = 65;

printf("Outputting ASCII value 65: %c", MyChar);

}

Outputting ASCII value 65: A

However, using %c you can at any time pass the character itself, not just the ASCII equivalent. You simply need to enclose it in single quotes ( ' ) and store it in a char type of variable:

#include

void main(void)

{

char MyChar = 'A';

printf("Outputting character A: %c", MyChar);

}

The output being:

Outputting character A: A

If you're trying to output more than one character you will need to enclose it in double quotes ( " ) and use %s (string) instead of %c (char):

#include

void main(void)

{

printf("Geek%s", "pedia");

}

Or if you store the string pedia in a char variable:

#include

void main(void)

{

char MyString[50] = "pedia";

printf("Geek%s", MyString);

}

No matter if you use a variable or pass the string directly, the result is the same:

Geekpedia

printf() is even capable of showing the address of a variable, thus showing the pointer of that variable. This can be seen in the following example: