Sams Teach Yourself C in 21 Days

Accepting Keyboard Input ..................................................................................

Most C programs require some form of input from the keyboard (that is, from the stdin

stream). Input functions are divided into a hierarchy of three levels: character input, line

input, and formatted input.

Character Input ..............................................................................................

The character input functions read input from a stream one character at a time. When

called, each of these functions returns the next character in the stream, or EOFif the end

of the file has been reached or an error has occurred. EOFis a symbolic constant defined

in stdio.h as -1. Character input functions differ in terms of buffering and echoing.

• Some character input functions are buffered. This means that the operating system
  holds all characters in a temporary storage space until you press Enter, and then the
  system sends the characters to the stdinstream. Others are unbuffered,meaning
  that each character is sent to stdinas soon as the key is pressed.


• Some input functions automatically echoeach character to stdoutas it is received.
  Others don’t echo; the character is sent to stdinand not stdout. Because stdout
  is assigned to the screen, that’s where input is echoed.
  The uses of buffered, unbuffered, echoing, and nonechoing character input are explained
  in the following sections.

Thegetchar()Function

The function getchar()obtains the next character from the stream stdin. It provides

buffered character input with echo, and its prototype is

int getchar(void);

The use of getchar()is demonstrated in Listing 14.2. Notice that the putchar()func-

tion, explained in detail later today, simply displays a single character on-screen.

LISTING14.2 getchar.c. Thegetchar()function

1: /* Demonstrates the getchar() function. */

2:

3: #include <stdio.h>

4:

5: int main( void )

6: {

7: int ch;

8:

9: while ((ch = getchar()) != ‘\n’)

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