Formatted I/O functions in C

printf() function:

• printf() function is used to print the “character, string, float, integer, octal and hexadecimal values” onto the output screen.
• We use printf() function with %d format specifier to display the value of an integer variable.
• Similarly %c is used to display character, %f for float variable, %s for string variable, %lf for double and %x for hexadecimal variable.
• To generate a newline,we use “\n” in C printf() statement.

Example program for C printf() function:

#include <stdio.h> int main() { char ch = ‘A’; char str[20] = “fresh2refresh.com”; float flt = 10.234; int no = 150; double dbl = 20.123456; printf(“Character is %c \n”, ch); printf(“String is %s \n” , str); printf(“Float value is %f \n”, flt); printf(“Integer value is %d\n” , no); printf(“Double value is %lf \n”, dbl); printf(“Octal value is %o \n”, no); printf(“Hexadecimal value is %x \n”, no); return 0; }                                                                                                                                                                                                   .

Output:

Character is A String is fresh2refresh.com Float value is 10.234000 Integer value is 150 Double value is 20.123456 Octal value is 226 Hexadecimal value is 96                                                                                                                                                                   .

You can see the output with the same data which are placed within the double quotes of printf statement in the program except

• %d got replaced by value of an integer variable  (no),

• %c got replaced by value of a character variable  (ch),

• %f got replaced by value of a float variable  (flt),

• %lf got replaced by value of a double variable  (dbl),

• %s got replaced by value of a string variable  (str),

• %o got replaced by a octal value corresponding to integer variable  (no),

• %x got replaced by a hexadecimal value corresponding to integer variable

• \n got replaced by a newline.

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C – printf and scanf

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• printf() and scanf() functions are inbuilt library functions in C which are available in C library by default. These functions are declared and related macros are defined in “stdio.h” which is a header file.
• We have to include “stdio.h” file as shown in below C program to make use of these printf() and scanf() library functions.

1. C printf() function:

• printf() function is used to print the “character, string, float, integer, octal and hexadecimal values” onto the output screen.
• We use printf() function with %d format specifier to display the value of an integer variable.
• Similarly %c is used to display character, %f for float variable, %s for string variable, %lf for double and %x for hexadecimal variable.
• To generate a newline,we use “\n” in C printf() statement.

Note:

• C language is case sensitive. For example, printf() and scanf() are different from Printf() and Scanf(). All characters in printf() and scanf() functions must be in lower case.

Example program for C printf() function:

#include <stdio.h> int main() { char ch = ‘A’; char str[20] = “fresh2refresh.com”; float flt = 10.234; int no = 150; double dbl = 20.123456; printf(“Character is %c \n”, ch); printf(“String is %s \n” , str); printf(“Float value is %f \n”, flt); printf(“Integer value is %d\n” , no); printf(“Double value is %lf \n”, dbl); printf(“Octal value is %o \n”, no); printf(“Hexadecimal value is %x \n”, no); return 0; }                                                                                                                                                                                                   .

Output:

Character is A String is fresh2refresh.com Float value is 10.234000 Integer value is 150 Double value is 20.123456 Octal value is 226 Hexadecimal value is 96                                                                                                                                                                   .

You can see the output with the same data which are placed within the double quotes of printf statement in the program except

• %d got replaced by value of an integer variable  (no),

• %c got replaced by value of a character variable  (ch),

• %f got replaced by value of a float variable  (flt),

• %lf got replaced by value of a double variable  (dbl),

• %s got replaced by value of a string variable  (str),

• %o got replaced by a octal value corresponding to integer variable  (no),

• %x got replaced by a hexadecimal value corresponding to integer variable

• \n got replaced by a newline.

2. C scanf() function:

• scanf() function is used to read character, string, numeric data from keyboard
• Consider below example program where user enters a character. This value is assigned to the variable “ch” and then displayed.

• Then, user enters a string and this value is assigned to the variable ”str” and then displayed.

Example program for printf() and scanf() functions in C:

#include <stdio.h> int main() { char ch; char str[100]; printf(“Enter any character \n”); scanf(“%c”, &ch); printf(“Entered character is %c \n”, ch); printf(“Enter any string ( upto 100 character ) \n”); scanf(“%s”, &str); printf(“Entered string is %s \n”, str); }                                                                                                                                                                                                    .

Output:

Enter any character a Entered character is a Enter any string ( upto 100 character ) hai Entered string is hai                                                                                                                                                                        .

• The format specifier %d is used in scanf() statement. So that, the value entered is received as an integer and %s for string.
• Ampersand is used before variable name “ch” in scanf() statement as &ch.
• It is just like in a pointer which is used to point to the variable.

Variations in Output for integer an floats

Integer and floating-points can be displayed in different formats in C programming as:

#include<stdio.h>
int main(){
    printf("Case 1:%6d\n",9876);      
/*  Prints the number right justified within 6 columns  */
    printf("Case 2:%3d\n",9876);      
/* Prints the number to be right justified to 3 columns but, there are 4 digits so number is not right justified  */
    printf("Case 3:%.2f\n",987.6543);
/* Prints the number rounded to two decimal places */
    printf("Case 4:%.f\n",987.6543);
/* Prints the number rounded to 0 decimal place, i.e, rounded to integer */
    printf("Case 5:%e\n",987.6543);
/* Prints the number in exponential notation(scientific notation) */
    return 0;
}

Output

Case 1:  9876
Case 2:9876
Case 3:987.65
Case 4:988
Case 5:9.876543e+002