Programming in C - 2. Input/Output Operations

C language does not have any built-in Input- Output (I/O) statements as a part of its syntax.
All the Input/Output operations are carried out through functions calls such as printf() and scanf()

scanf() 

• General purpose console input function. Also used to input a data line containing mixed mode data.
• syntax : scanf ("format specifier", variable_list); // end with semi-colon and case-sensitive.
• 'format specifier' specifies the field format in which the data has to be entered.
• 'variable list' specifies the address of the location where the data is stored.
• use '%' before format sepecifier and '&' before a variable name

Format Specifier

• It contains specifications for the interpretation of input data.
• '%' conversion character.
• list of format specifier
• %c To read a single character
• %d To read a decimal integer
• %e To read a floating point value
• %f  To read a floating point number
• %g To read a floating point value
• %o to read an octal value
• %x To read an Hexadecimal value
• %s To read a String
• %u To read an unsigned integer
• For reading a string 
• scanf("%s", &st); // st contains the string value
• For reading two values
• scanf("%d,%d",&a,&b);\
• Features :
• format specification and variable list must correctly match the same order
• The format specifier must be separated by space or comma and vairable list by comma
• use of invalid match between format specifier and variable list will make the scanf() to terminate the reading of data

printf()

• syntax : printf ( " format specifier ", variable list);
• never takes the print to the new line so we use '\n' for a new line
• eg : printf(" no of chocolates = %d \n no of sweets = %d",&a,&b); // ouput : no of chocolates = 12 [next line ] no of sweets = 13 // where a = 12 and b =13
• list of escape sequences like \n 
• \b     back space
• \f      Form feed
• \n     New line
• \r     Carriage return
• \t     Horizontal tab
• \"     Double quote mark
• \'     single quote mark
• \0    null
• \\     Back slash
• \v    Vertical tab
• \a    Alert ( rings a bell)
• \o    Octal constant
• \x     Hexadecimal constant

Sample Program :

First you need :

Compiler :

online compiler : codepad.org

offline compiler : http://edn.embarcadero.com/article/20633 (borlan c++ compiler)

                           http://www.digitalmars.com/ (digital mars c compiler)

01 #include <stdio.h> // imports the header file stdio.h which contains the definitions of scanf() and printf()

                                     functions.

02 void main() // execution of the program begins in the main() function

03 {

04       printf(" Hello world ");

05 } // main() ends here

output : Hello world 

Next Article : Programming in C - 3. Control Statements and Arrays