C printf()
Formatted Output and the printf() function
One of the common task in every program is the printing of output. We use the output to request input from a user and later display the status/result, computations etc. In C programming there are several functions for printing formatted output.
The printf() function is used to format and print a series of characters and values to the standard output.
Syntax:
int printf(const char *format-string, argument-list);
Parameters:
Name | Description |
---|---|
format | The format argument is a string containing C language conversion specifications. The conversion specification specifies the notation, alignment, significant digits, field width, and other aspects of the output format. To represent non-printing characters, such as newlines and tabs, the format string may contain escape characters. Below are the details. |
argument-list | Depending on the format string, the function may require additional arguments. |
Format strings specify notation, alignment, significant digits, field width, and other aspects of output formats. It can contain ordinary alphanumeric characters; along with escape characters, conversion specifiers, and other characters. Format specifications are made up of a the percent sign (%) followed by one of the following conversion operators, which determine what printf does with its arguments.
Conversion Specifiers:
Specifier | Description |
---|---|
%% | Print a single % character |
%c | Convert an int to an unsigned character and print the resulting character |
%d or %i | Print an int as a signed decimal number |
%u | Print an unsigned as an unsigned decimal number |
%o | Print an unsigned as an unsigned octal number |
%x | Hexadecimal notation (using lowercase letters a-f) |
%X | Hexadecimal notation (using uppercase letters A-F) |
%e | Exponential notation (using a lowercase e as in 3.1415e+00) |
%E | Exponential notation (using an uppercase E as in 3.1415E+00) |
%f | Print a double using a decimal format like [-]ddd.ddd |
%g | The more compact of %e or %f, insignificant zeros do not print. |
%G | Same as g, but using an uppercase E |
%s | Print the string pointed to by a char * |
%p | Print a void * argument in hexadecimal (ANSI C only) |
%n | Store the number of characters printed at this point in the integer pointed to by the int * argument. Nothing is printed. (ANSI C only). |
Conversion Flags:
You can control the alignment of the output using any of these optional flags.
Flag | Format | Example |
---|---|---|
+ (plus) | Always prints a sign character (+ or -). | %+7.2d |
- (minus) | Left-justifies the converted argument in its field. | %-7.2d |
0 (Zero) | Pad with zeros rather than spaces. | %07.2d |
# (hash) | Use an alternate form for the output. The effect differs depending on the conversion specifier.
|
Conversion width and precision:
By including these options in the format string, you can control the width and precision of the output:
Character | Description | Example |
---|---|---|
Field width | A digit string specifying the minimum number of digits to be printed. | %5f |
Precision | A digit string including a period (.) specifying the number of digits to be printed to the right of the decimal point. | %5.2f |
Some conversion operators may also be preceded by a size specification:
- h indicates that the argument associated with a d, i, o, u, x or X operator is a short or unsigned short.
- l indicates that the argument associated with a d, i, o, u, x or X operator is a long or unsigned long.
- L indicates that the argument associated with a e, E, f, g or G operator is a long double (ANSI C only)
Escape sequences in C:
An escape sequence is a series of characters that represents a special character. It begins with a backslash character (\), which indicates that the character(s) that follow the backslash character should be treated in a special way. C uses escape sequences within a format string to print certain special characters. For example \n moves the output position to the beginning of the next line. The following is a list of escape sequences.
Escape sequence | Action |
---|---|
\n | prints a new line |
\b | backs up one character |
\t | moves the output position to the next tab stop |
\\ | prints a backslash |
\" | prints a double quote |
\' | prints a single quote |
Return value
- Returns the number of bytes printed.
Examples: printf() function
Function | Result |
---|---|
printf("%%|\n"); 1 | %| |
printf("%c|\n", 'p'); | p| |
printf("%5c|\n", 'p'); | p| |
printf("%-5c|\n", 'p'); | p | |
printf("%d|\n", 234567); | 234567 |
printf("%5d|\n", 234567); | 234567 |
printf("%6d|\n", 234567); | 234567 |
printf("%6d|\n", 1); | 1 |
printf("%4.2d|\n", 234567); | 234567 |
printf("%6.2d|\n", 234567); | 234567 |
printf("%6.2d|\n", 1); | 01 |
printf("%06d|\n", 234567); | 234567 |
printf("%-6d|\n", 234567); | 234567 |
printf("% 6d|\n", 234567); | 234567 |
printf("%+6d|\n", 234567); | +234567 |
printf("%08d|\n", 234567); | 00234567 |
printf("%-8d|\n", 234567); | 234567 |
printf("% 8d|\n", 234567); | 234567 |
printf("%+8d|\n", 234567); | +234567 |
printf("%-6.2d|\n", 234567); | 234567 |
printf("% 6.2d|\n", 234567); | 234567 |
printf("%+6.2d|\n", 234567); | +234567 |
printf("%i|\n", 234567); | 234567 |
printf("%5i|\n", 234567); | 234567 |
printf("%6i|\n", 234567); | 234567 |
printf("%6i|\n", 1); | 1 |
printf("%o|\n", 234567); | 712107 |
printf("%4o|\n", 234567); | 712107 |
printf("%5o|\n", 234567); | 712107 |
printf("%4.2o|\n", 234567); | 712107 |
printf("%5.2o|\n", 234567); | 712107 |
printf("%#5o|\n", 234567); | 0712107 |
printf("%05o|\n", 234567); | 712107 |
printf("%-5o|\n", 234567); | 712107 |
printf("%#8o|\n", 234567); | 0712107 |
printf("%08o|\n", 234567); | 00712107 |
printf("%-8o|\n", 234567); | 712107 |
printf("%-5.2o|\n", 234567); | 712107 |
printf("%x|\n", 234567); | 39447 |
printf("%4x|\n", 234567); | 39447 |
printf("%5x|\n", 234567); | 39447 |
printf("%X|\n", 234567); | 39447 |
printf("%4.2x|\n", 234567); | 39447 |
printf("%5.2x|\n", 234567); | 39447 |
printf("%#5x|\n", 234567); | 0x39447 |
printf("%05x|\n", 234567); | 39447 |
printf("%-5x|\n", 234567); | 39447 |
printf("%#8x|\n", 234567); | 0x39447 |
printf("%08x|\n", 234567); | 00039447 |
printf("%-8x|\n", 234567); | 39447 |
printf("%#8X|\n", 234567); | 0X39447 |
printf("%08X|\n", 234567); | 00039447 |
printf("%-8X|\n", 234567); | 39447 |
printf("%-5.2x|\n", 234567); | 39447 |
printf("%e|\n", 23456.7645); | 2.345676e+004 |
printf("%4e|\n", 23456.7645); | 2.345676e+004 |
printf("%5e|\n", 23456.7645); | 2.345676e+004 |
printf("%E|\n", 23456.7645); | 2.345676E+004 |
printf("%4.2e|\n", 23456.7645); | 2.35e+004 |
printf("%5.2e|\n", 23456.7645); | 2.35e+004 |
printf("%4.2E|\n", 23456.7645); | 2.35E+004 |
printf("%5.2E|\n", 23456.7645); | 2.35E+004 |
printf("%#5e|\n", 23456.7645); | 2.345676e+004 |
printf("%05e|\n", 23456.7645); | 2.345676e+004 |
printf("%-5e|\n", 23456.7645); | 2.345676e+004 |
rintf("% 5e|\n", 23456.7645); | 2.345676e+004 |
printf("%+5e|\n", 23456.7645); | +2.345676e+004 |
printf("%#8e|\n", 23456.7645); | 2.345676e+004 |
printf("%08e|\n", 23456.7645); | 2.345676e+004 |
printf("%-8e|\n", 23456.7645); | 2.345676e+004 |
printf("% 8e|\n", 23456.7645); | 2.345676e+004 |
printf("%+8e|\n", 23456.7645); | +2.345676e+004 |
printf("%#8E|\n", 23456.7645); | 2.345676E+004 |
printf("%08E|\n", 23456.7645); | 2.345676E+004 |
printf("%-8E|\n", 23456.7645); | 2.345676E+004 |
printf("% 8E|\n", 23456.7645); | 2.345676E+004 |
printf("%+8E|\n", 23456.7645); | +2.345676E+004 |
printf("%#5.2e|\n", 23456.7645); | 2.35e+004 |
printf("%05.2e|\n", 23456.7645); | 2.35e+004 |
printf("%-5.2e|\n", 23456.7645); | 2.35e+004 |
printf("% 5.2e|\n", 23456.7645); | 2.35e+004 |
printf("%+5.2e|\n", 23456.7645); | +2.35e+004 |
printf("%f|\n", 23456.7645); | 23456.764500 |
printf("%4f|\n", 23456.7645); | 23456.764500 |
printf("%5f|\n", 23456.7645); | 23456.764500 |
printf("%4.2f|\n", 23456.7645); | 23456.76 |
printf("%5.2f|\n", 23456.7645); | 23456.76 |
printf("%#5f|\n", 23456.7645); | 23456.764500 |
printf("%05f|\n", 23456.7645); | 23456.764500 |
printf("%-5f|\n", 23456.7645); | 23456.764500 |
printf("% 5f|\n", 23456.7645); | 23456.764500 |
printf("%+5f|\n", 23456.7645); | +23456.764500 |
printf("%#8f|\n", 23456.7645); | 23456.764500 |
printf("%08f|\n", 23456.7645); | 23456.764500 |
printf("%-8f|\n", 23456.7645); | 23456.764500 |
printf("% 8f|\n", 23456.7645); | 23456.764500 |
printf("%+8f|\n", 23456.7645); | +23456.764500 |
printf("%#5.2f|\n", 23456.7645); | 23456.76 |
printf("%05.2f|\n", 23456.7645); | 23456.76 |
printf("%-5.2f|\n", 23456.7645); | 23456.76 |
printf("% 5.2f|\n", 23456.7645); | 23456.76 |
printf("%+5.2f|\n", 23456.7645); | +23456.76 |
printf("%g|\n", 23456.7645); | 23456.8 |
printf("%4g|\n", 23456.7645); | 23456.8 |
printf("%5g|\n", 23456.7645); | 23456.8 |
printf("%G|\n", 23456.7645); | 23456.8 |
printf("%4.2g|\n", 23456.7645); | 2.3e+004 |
printf("%5.2g|\n", 23456.7645); | 2.3e+004 |
printf("%#5g|\n", 23456.7645); | 23456.8 |
printf("%05g|\n", 23456.7645); | 23456.8 |
printf("%-5g|\n", 23456.7645); | 23456.8 |
printf("% 5g|\n", 23456.7645); | 23456.8 |
printf("%+5g|\n", 23456.7645); | +23456.8 |
printf("%#8g|\n", 23456.7645); | 23456.8 |
printf("%08g|\n", 23456.7645); | 023456.8 |
printf("%-8g|\n", 23456.7645); | 23456.8 |
printf("% 8g|\n", 23456.7645); | 23456.8 |
printf("%+8g|\n", 23456.7645); | +23456.8 |
printf("%#8G|\n", 23456.7645); | 23456.8 |
printf("%08G|\n", 23456.7645); | 023456.8 |
printf("%-8G|\n", 23456.7645); | 23456.8 |
printf("% 8G|\n", 23456.7645); | 23456.8 |
printf("%+8G|\n", 23456.7645); | +23456.8 |
printf("%#5.2g|\n", 23456.7645); | 2.3e+004 |
printf("%05.2g|\n", 23456.7645); | 2.3e+004 |
printf("%-5.2g|\n", 23456.7645); | 2.3e+004 |
printf("% 5.2g|\n", 23456.7645); | 2.3e+004 |
printf("%+5.2g|\n", 23456.7645); | +2.3e+004 |
printf("%s|\n", "ABCDE"); | ABCDE |
printf("%4s|\n", "ABCDE"); | ABCDE |
printf("%5s|\n", "ABCDE"); | ABCDE |
printf("%4.2s|\n", "ABCDE"); | AB |
printf("%5.2s|\n", "ABCDE"); | AB |
printf("%-5s|\n", "ABCDE"); | ABCDE |
printf("%-8s|\n", "ABCDE"); | ABCDE |
printf("%-5.2s|\n", "ABCDE"); | AB |
printf("%p|\n", "ABCDE"); | 000000000040537E |
printf("%4p|\n", "ABCDE"); | 000000000040537E |
printf("%5p|\n", "ABCDE"); | 000000000040537E |
printf("%-5p|\n", "ABCDE"); | 000000000040537E |
printf("%-8p|\n", "ABCDE"); | 000000000040537E |
To use the printf() function we must include the stdio library in the source code. To do this just place the following code at the beginning of your program.
#include <stdio.h>
To print a simple message in computer screen you might call printf() function as follows:
#include <stdio.h>
main()
{
printf ("You are learning printf() function");
}
Output:
You are learning printf() function
In the above examples, the cursor will remain at the end of the printed output. If you repeat the above code in the following way the second message would appear immediately after the first one.
#include <stdio.h>
main()
{
printf("You are learning printf() function");
printf("You are learning printf() function");
}
Output:
You are learning printf() function You are learning printf() function
Escape sequences in C
You will get an idea of using the escape sequences from the following example.
#include<stdio.h>
main()
{
printf("Create a new line\n");
printf("Print a double quotes (\") within a string\n");
printf("Print a single quotes (\') within a string\n");
printf("Print a Backslash\\ within a string\n");
printf("Using Backspace\b within a string\n");
printf("Using\tTab within a string\n");
}
Output:
Create a new line Print a double quotes (") within a string Print a single quotes (') within a string Print a Backslash\ within a string Using Backspace within a string Using Tab within a string
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