Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 6 ■ Characters
A word of caution: we might be tempted to write the following:
printf("The first character is %c \n", getchar());
printf("Its code is %d \n", getchar()); // wrong
But if we did, and assuming that Hello is typed as input, these statements will print:
The first character is H
Its code is 101
Why? In the first printf, getchar returns H, which is printed. In the second printf, getchar
returns the next character, which is e; it is e’s code (101) that is printed.
In Program P6.1, we could use an int variable (n, say) instead of ch and the program would
work in an identical manner. If an int variable is printed using %c, the last (rightmost) 8 bits of the
variable are interpreted as a character and this character is printed. For example, the code for H is
72 which is 01001000 in binary, using 8 bits. Assuming n is a 16-bit int, when H is read, the value
assigned to n will be
00000000 01001000
If n is now printed with %c, the last 8 bits will be interpreted as a character which, of course, is H.
Similarly, if an int value n is assigned to a char variable (ch, say), the last 8 bits of n will be
assigned to ch.
As mentioned, getchar returns the integer value of the character read. What does it return
when the user presses “Enter” or “Return” on the keyboard? It returns the newline character \n,
whose code is 10. This can be seen using Program P6.1. When the program is waiting for you
to type data, if you press the “Enter” or “Return” key only, the first lines of output would be as
follows (note the blank line):
The first character is
Its code is 10
Why the blank line? Since ch contains \n, the statement
printf("\nThe first character is %c \n", ch);
is effectively the same as the following (with %c replaced by the value of ch)
printf("\nThe first character is \n \n");
The \n after is ends the first line and the last \n ends the second line, effectively printing a
blank line. Note, however, that the code for \n is printed correctly.
In Program P6.1, we read just the first character. If we want to read and print the first three
characters, we could do this with Program P6.2.
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