scanf and printf in C Language Lecture-5

King Fahd University of Petroleum and Minerals Affiliated Colleges at Hafr Al-Batin (ACHB / HBCC ) Computer Science & Engineering Technology Unit (CSET) CSET101: Computer programming scanf and printf in C Language Lecture-5

Introduction • printf (print formatted) function • printf function performs output to the standard output device, typically monitor. • printf requires a format string that defines text to print out and specifications on how to print out values of variables. • Examples: • printf("the ASCII value of %c is %d", 65, 65); // code of A is 65 • printf("the size of int is %d bytes", sizeof(int)); • printf(“My age is %f years”, age); //age as float variable • scanf (scan formatted) function • scanf performs input from the standard input device, typically keyboard. • scanf also requires format string or control string that controls how input will be performed. • scanf does type conversion from ASCII to the type specified in format string. • Examples • scanf(“%c”, &initials); // note the & symbol before variable • scanf(“%f”, &radius); // the & means address of • scanf(“%d %c %f %s”, &count, &code, &ratio, &name);

Introduction

Example-1 #include <stdio.h> void main() { int number; printf("Type in a number \n"); scanf("%d", &number); printf("The number you typed was %d\n", number); } ---------------------------------------------------------------------------- Sample Program Output :- Type in a number 23 The number you typed was 23

Explanation of Example-1 • An integer variable called number is defined. • A prompt to enter in a number is then printed using the statement : • printf("Type in a number \n:"); • The scanf routine, which accepts the response, has two arguments. • The first ("%d") specifies what type of data type is expected (i.e. , char, int, or float). • The second argument (&number) specifies the variable into which the typed response will be placed. In this case the response will be placed into the memory location associated with the variable number. • This explains the special significance of the & character (which means the address of).

Example-2 #include < stdio.h > main() { int sum; char letter; float money; printf("Please enter an integer value "); scanf("%d", &sum ); printf("Please enter a character "); scanf(" %c", &letter ); printf("Please enter a float variable "); scanf("%f", &money ); printf("\nThe variables you entered were\n"); printf("value of sum = %d\n", sum ); printf("value of letter = %c\n", letter ); printf("value of money = %f\n", money ); } Sample Program Output:- Please enter an integer value 34 Please enter a character W Please enter a float variable 32.3 The variables you entered were value of sum = 34 value of letter = W value of money = 32.300000

Explanation of Example-2 • This program illustrates several important points. • the c language provides no error checking for user input. The user is expected to enter the correct data type. For instance, if a user enters a character when an integer value was expected, the program may enter an infinite loop or abort abnormally. • It is up to the programmer to validate data for correct type and range of values.

Formatted Input • Formatted input refers to an input data that has been arranged in a particular format. • This is possible in C by using scanf function. • The general form of scanf is: scanf(“control string” , arg 1, arg 2, ………., arg n); • The control stringspecifies the field format consisting of conversion character ‘%’ • The arg 1, arg 2, ………., arg n specify the address location. • The control string and arguments are separated by commas( , ).

Inputting Integer Numbers (%d) • The field specification for reading an integernumber is %d • The percent sign (%) indicates that a conversion specification follows. • d known as data type character, indicates integer mode. • For example: scanf(“%d %d”, &num1, &num2);

Inputting Real Numbers (%f) • The field specification for reading an real number is %f • The percent sign (%) indicates that a conversion specification follows. • f known as data type float, indicates real mode. • For example: scanf(“%f %f %f”, & x, & y, & z);

Inputting Character Strings(%c or %s) • The field specification for reading character is %c or %s • The percent sign (%) indicates that a conversion specification follows. • c or s known as data type character, indicates character or string mode. • For example: scanf(“%c %c”, &num1, &num2);

Reading mixed Data Types • It is possible to used one scanf statement to input a data line containing mixed mode data. • In such cases, care should be taken that the input data items match the control specification in order and type. • For example: scanf(“%d %c %f %s”, &count, &code, &ratio, &name); • Will read the data: 15 p 1.573 coffee

scanf and printf in C Language Lecture-5