Displaying strings in screen
The two most frequently used ways to display text strings is to use C's library functions printf() and puts().
• The printf() Function
The printf() function, part of the standard C library, is perhaps the most versatile way for a program to display data on-screen.
• Printing a text message on-screen is simple. Call the printf() function, passing the desired message enclosed in double quotation marks. For example,
printf("An error has occurred!");
Displays : An error has occurred!
• Similarly, puts() functions can also be used to display string in screen as:
puts(“An error has occurred!”);
• printf() function is used to display the values of variables,constants with formatting , but puts only prints text string in screen.
Conversion specifications
• Displaying the value of program variables in screen is a little more complicated than displaying only a message.
• For example , if we have to display value of an integer variable x in screen, we can write as follows:
printf("The value of x is %d", x);
• Assume that value at variable x is 15 then the above statements display as:
The value of x is 15
• In above statement, %d is called the conversion specification used for the value of integer variable to be printed at that position.
A program to display value with format specifier
/*program */
#include< stdio.h>
int main()
{
int x=10;
float f=3.56;
char ch=‘X’;
printf("Decimal NO x =%d",x);
printf("\n Octal No x = %o",x);
printf("\nHex NO x= %X",x);
printf("\nFloat No f= %G",f);
printf("\nFloat NO f =%f",f);
printf("\nFloat No f =%E",f);
printf("\nSingle Char ch = %c“,ch);
printf("\nString : %s","C-Program");
return 0;
}
Character Input/Output
The getchar() and putchar() Functions
• The int getchar(void) function reads the next available character from the input buffer and returns it as an integer.Example: c = getchar( );
• This function reads only single character at a time. We can use this method in the loop in case of reading more than one character from the input buffer.
• The int putchar(int c) function puts the passed character on the screen and returns the same character.
Example putchar(c);
• This function puts only single character at a time. We can use this method in the loop in case to display more than one character on the screen.
Reading and writing a character
The scanf() and printf() Functions for read and write:
char c= ‘$’; /*declaration of char variable c */
printf(“%c”,c); /*Prints character $ */
scanf(“%c”,&c); for input a character in c
printf(“%c”,c); for output a character in c
getc() and putc() character I/O Function
Function getc() : It reads a single character from the input and return an integer value. If it fails, it returns EOF. The syntax of getc() in C language is ,
int getc(FILE *stream);
Function putc(): It prints the passed character in screen
Example of getc() in C language
#include< stdio.h>
int main ()
{
char ch;
printf("Enter the character: ");
ch = getc(stdin);
printf("Character entered: ");
putc(ch, stdout);
return(0);
}
Output
Enter the character: a
Character entered: a
The getch() Function
getch(): The function getch() is a non-standard function. It is declared in “conio.h” header file.
• Mostly it is used by Turbo C. It is not a part of C standard library.
• It immediately returns the entered character without even waiting for the enter key.
• Here is an example of getch() in C language:
#include < stdio.h>
#include< conio.h>
int main()
{
char c;
printf("Enter the character : ");
c= getch();
printf("Entered character : %c", c);
return 0;
}
Output
Enter the character :
Entered character : #
The getche() Function
getche():Like getch(), the getche() function is also a non-standard function and declared in “conio.h” header file.
• It reads a single character from the keyboard and returns it immediately without even waiting for enter key.
• Below is an example of getche() in C language.
#include < stdio.h>
#include< conio.h>
int main()
{
char val;
printf("Enter the character : ");
val = getche();
printf(“ Entered character : %c", val);
return 0;
}
Output
• Enter the character : s Entered character : s
Input data with scanf()
Most programs need to input data from the keyboard.
• The most flexible way our program can read numeric data from the keyboard is by using the scanf() library function.
• The scanf() function reads data from the keyboard according to a specified format and assigns the input data to one or more program variables.
• Like printf(), scanf() uses a same format string to describe the format of the input as
• For example, the statement scanf("%d", &x);
reads a decimal integer from the keyboard and assigns it to the integer variable x.
• Likewise, the following statement reads a floating-point value from the keyboard and assigns it to the variable rate:
scanf("%f", &rate);
scanf()
The & symbol is C's address-of operator, which specifies the address of the variable stated
• The scanf() requires the & symbol before each numeric variable name in its argument list
• A single scanf() can input more than one value if we include multiple conversion specifiers in the format string and variable names (again, each preceded by & in the argument list).
• The following statement inputs an integer value and a floating-point value and assigns them to the variables x and rate, respectively: scanf("%d %f", &x, &rate);
• When multiple variables are entered, scanf() uses white space to separate input into fields. White space can be spaces, tabs, or new lines.
• Each conversion specifier in the scanf() format string is matched with an input field and the end of each input field is identified by white space.
• This gives us considerable flexibility. In the preceding scanf(), we could enter 10 12.45
• Or or this: 10
12.45
An example of printf()/scanf()
#include < stdio.h>
Int main()
{
float y;
int x;
puts( "Enter a float, then an int" );
scanf( "%f %d", &y, &x);
printf( "\nYou entered %f and %d ", y, x );
return 0;
}
Output:
Enter a float, then an int: 4.56 45
You entered 4.560000 and 45
String Input with gets()
gets(): The gets() function reads a line from stdin(standard input) into the buffer pointed to by string pointer until either a terminating newline or EOF (end of file) occurs.
e.g.
#include< stdio.h>
int main()
{
/* character array of length 100 */
char str[100]; /* Will discussed later in chapter array in detail */
printf("Enter a string : ");
gets( str );
printf(“You Entered String: ”);
puts( str );
return 0;
}
Output:
Enter a string: patan campus
You Entered String: patan campus
Input strings with scanf()
We can use scanf() function to read text string from standard input. The syntax of scanf() for reading string literal is as below:
scanf(“%s”, string_variable);
Example:
#include< stdio.h>
int main()
{
/* character array of length 100 */
char str[100]; /* Will discussed later in chapter array in detail */
printf("Enter a string : ");
scanf("%s",str) ;
printf("You Entered String: %s",str);
return 0;
}
Note: Unlike gets(), scanf () reads string until any white space character is encountered.
Output: Enter a string: Patan
You Entered String: Patan
In previous example if we give the input with white space, it takes input only up to that white space character , rest is ignored.
• To read string with white space up to one line, scanf() function can be written as:
scanf("%[^\n]", string_variable) ;
Example:
#include< stdio.h>
int main()
{
/* character array of length 100 */
char str[100]; /* Will discussed later in chapter array in detail */
printf("Enter a string : ");
scanf("%[^\n]",str) ;
printf("You Entered String: %s",str);
return 0;
}
Input strings with scanf()
Output
Enter a string: Patan Campus
You Entered String: Patan Campus
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