Formatted Output Functions

printf()

printf( ) is a standard output function, displayed output into the console or standard output device computer screen. The prototype of the printf( ) function is given below:

int printf (format_string, list_of_expressions);

Details of Arguments

• format_string - it represents the layout of what's being printed as string and must be passed inside the double quote (" ")

• list_of_expressions - it is a comma separated list of variables or expressions yielding the result to be inserted into the output

Return Value

• printf( ) returns an integer value as number characters it's printed into the console

Printing Values

To output an integer value %d is used in the format string, and an integer expression in the list_of_expressions.

int number = 45;

printf(“%d”, number);

It prints 45 to the console. We can also print a message as a string before printing the integer number. For example,

printf(“The Number is = %d”, number);

It prints the output as: The Number is = 45. To print an unsigned integer (positive values) %u format specifier can be used instead of %d (used to print negative and positive integer numbers). For example,

unsigned int k = 34;

printf("k = %u",k);

It prints the output as: k = 34. If we pass an negative value as expression and %u is used as format specifier, then negative value will be converted to a known unsigned integer value. For example,

printf("%u",-1);

It prints the output as 4294967295, -1 gets converted to a known unsigned int value. That’s why format specifiers are also called conversion specifiers. To print a character the format specifier %c is used and to print a string as message no format specifier is required. We simply put the message inside the double quote. To print a single floating-point number upto 6th decimal point %f is used. For example,

#include <stdio.h>

int main(){

char ch = ‘A’;

float f = 5.6;

printf(“The Output is ”);

printf(“ch = %c f = %f”, ch, f);

}

sprintf()

sprintf( ) stands for string print. Like printf( ) instead of print the output to the console it prints the output to a character buffer. The prototype of the sprintf( ) function is given below:

int sprintf(char *buffer, format_string, list_of_expressions);

Details of Arguments

• *buffer - represents a character array and used to save the output

• format_string - it represents the layout of what's being printed as string and must be passed inside the double quote (“ ”)

• list_of_expressions - it is a comma separated list of variables or expressions yielding the result to be inserted into the output

Return Value

• int - returns the number characters written in the buffer

In C/C++ character buffers are represented using char arrays and also called null terminated strings. For example,

#include<stdio.h>

int main(){

int num1 = 3;

int num2 = 4;

char buffer[20];//declaration of a char buffer as string

sprintf(buffer, "The sum of %d + %d = %d", num1,num2,num1+num2);//line4

printf("%s",buffer);//prints the output from buffer

}

To print the buffer %s format specifier is used. %s is used to print a char buffer as string. The output of code is: The sum of 3 + 4 = 7. This output is written to the char buffer using sprintf( ) formatted function at line4.

fprintf()

It is used to write the output to a file instead of a console like printf( ) function. The prototype of the function is as follows:

int fprintf(FILE *, format_string, list_of_expressions);

Details of Arguments

• FILE * - it is a file pointer pointing to a file stream to write the output.

• format_string - it represents the layout of what's being write as string to a file pointed by FILE pointer and must be passed inside the double quote (“ ”)

• list_of_expressions - it is a comma separated list of variables or expressions yielding the result to be inserted into the output

Writing Output to a file

Before writing the output to a file stream, the file needs to be created and opened in writing mode ( w ). To do that, a file must be opened first in the project directory or in a specified location. For example,

#include<stdio.h>

#include<stdlib.h>

int main( ){

FILE *ptr;

int year;

char str1[10] = "This is";

char str2[10] = "free";

char str3[10] = "study material";

ptr = fopen("abc.txt","w");

fprintf(ptr, "%s %s %s",str1, str2, str3);

}