36	Part I: Introduction to C Programming

The Helpful RULES Program

I just can’t let you go without a program in this chapter. To help you under­ stand the most easily offended C rules, I have summarized them in the follow­ ing program. It displays several lines of text that remind you of the basic rules of C that you know about:

#include <stdio.h>

int main()

{

printf(“Braces come in pairs!”); printf(“Comments come in pairs!”);

printf(“All statements end with a semicolon!”); printf(“Spaces are optional!”);

printf(“Must have a main function!”); printf(“C is done mostly in lowercase.\ It’s a case-sensitive language.”);

return(0);

}

Type the preceding source code into your editor. Save the code to disk as

RULES.C. Compile and run.

The resulting program is named RULES, and you can run it whenever you need a reminder about some basic C do’s and don’ts.

This program is really no different from those shown in previous chap­ ters. It merely has more printf() functions.

The final printf() function (in Line 10) may seem a little odd. That’s because it’s split between two lines. This weird contraption is covered later in this chapter.

The importance of being \n

Did you notice something odd about the output of the RULES program? Yes, it resembles an ugly clot of text:

Braces come in pairs!Comments come in pairs!All statements end with a semicolon!Spaces are optional!Must have

a main function!C is done mostly in lowercase. It’s a case-sensitive language.

The source code looks okay, but what’s missing from the output is the char­ acter you get when you press the Enter key, or what’s called the newline char­ acter. You have seen it before. It’s that weird \n thing:

Chapter 3: C Straight 37

\n

This line is C-speak for “Gimme a new line of text.” The n stands for new in new line (though they write it as one word: newline).

The program you just created, RULES.C, needs the \n character at the end of each line to ensure that each line is displayed on a line by itself on the screen. This addition makes the output of the RULES program easy to read.

Edit the RULES.C source code file again. Before the last double-quote in each printf() string, add the \n newline character.

If you’re good with search and replace, search for the “) (quote-paren) and replace it with \n”).

Save the file to disk and recompile it. The output should now be more pleasing:

Braces come in pairs! Comments come in pairs!

All statements end with a semicolon! Spaces are optional!

Must have a main function!

C is done mostly in lowercase. It’s a case-sensitive language.

In C, the \n character is used in a text string as though the Enter key were pressed.

It’s always \n with a little n. C is mostly lowercase.

The \n is called newline, though calling it “slash-n” or “backslash-n” is acceptable as long as you don’t say it aloud.

Table 24-1, in Chapter 24, lists other characters of a similar nature to \n.

Breaking up lines\ is easy to do

Another anomaly of the RULES program is that rogue \ character found at the end of the tenth line. When used to end a line, the sole \ tells the compiler that the rest of the line is merely continued on the line that follows. So, these two lines:

printf(“C is done mostly in lowercase\

It’s a case-sensitive language.\n”);

are both seen as one single line when it comes time to compile; all the compiler sees is this:

printf(“C is done mostly in lowercase It’s a case-sensitive

language.\n”);

38	Part I: Introduction to C Programming

You may find such a trick necessary for extra-long lines as your programs grow more complex. The \ simply lets you split up a long line between several lines in your source code. That can be handy.

Depending on how your editor and compiler behave, the result of splitting a line with a string of text in it may not be what you want. For example, the output on your screen may look like this:

Braces come in pairs! Comments come in pairs!

All statements end with a semicolon! Spaces are optional!

Must have a main function!

C is done mostly in lowercase. It’s a casesensitive language.

That happens because the split line includes a few tabs to indent things — which looks pretty in your source code, but looks like blech when the pro­ gram runs. The solution is merely to edit the source code so that the extra tabs are removed from the string of text.

To wit, change Lines 10 and 11 in the source code from this:

printf(“C is done mostly in lowercase.\

It’s a case-sensitive language.”);

to this:

printf(“C is done mostly in lowercase. \

It’s a case-sensitive language.”);

Note the extra space after the period in the first line (before the backslash), which keeps the two lines of text from running into each other. Save that mess. Compile and run. The output shall be most pleasing to the eye.

Do note that some programs elsewhere in this book may use the \ to split long lines.

Don’t worry about using the \ to split any lines. It’s a trick you see others use occasionally, but in my travels I prefer using a sideways-scrolling editor to splitting up long lines.

Although split lines are treated as a single line, any errors that happen on

either line are given their proper line number in the source code file. So, if a semicolon were missing at the end of Line 11 in the RULES.C example, the compiler would flag it on that line, not on the line before it.

Chapter 4

C What I/O

In This Chapter

Reading the keyboard

Understanding printf()

Creating formatted output

Understanding scanf()

Computers are all about input and output — the old I/O of days gone by, what the pioneers once sang about. The wimminfolk would want to dance

real slow. Maybe cry. It was a sentimental thing, y’all — something that fancy, dooded-up city slickers read about in dime magazines.

A-hem!

Input and output: You type something in and get a response, ask a question and get an answer, put in two dollars in coins and get your soda pop — things along those lines. This goes along with what I present in Chapter 3: It is your job as a programmer to write a program that does something. At this point in the learning process, triviality is okay. Soon, however, you begin to write pro­ grams that really do something.

Introduce Yourself to Mr. Computer

To meet the needs of input and output — the old I/O — you can try the follow­ ing program, WHORU.C — which is “who are you” minus a few letters. Please don’t go calling this program “horror-you” (which could be spelled another way, but this is a family book).

40	Part I: Introduction to C Programming

The purpose of this program is to type your name at the keyboard and then have the computer display your name on the screen, along with a nice, friendly greeting:

#include <stdio.h>

int main()

{

char me[20];

printf(“What is your name?”); scanf(“%s”,&me);

printf(“Darn glad to meet you, %s!\n”,me);

return(0);

}

Type the preceding source code into your editor. Double-check everything.

Don’t bother with any details just yet. Type and hum, if it pleases you.

Save the file to disk. Name it WHORU.C.

Don’t compile this program just yet. That happens in the next section.

The char me[20]; thing is a variable declaration. It provides storage for the information you enter (the I in I/O). You find out more about variables in Chapter 8.

The new function here is scanf(), which is used to read input from the keyboard and store it in the computer’s memory.

Left paren is the ( character. Right paren is the ) character. Paren is short for parenthesis or a type of steak sauce. (It’s also not a “real” word and is frowned on by English teachers of the high-and-tight bun.)

Compiling WHORU.C

Compile the WHORU.C source code. If you see syntax or other errors, doublecheck your source code with what is listed in this book. Ensure that you entered everything properly. Be on the lookout for jots and tittles — parentheses, double quotes, backslashes, percent signs, sneeze splotches, or other unusual things on your monitor’s screen.

If you need to fix any errors, do so now. Otherwise, keep reading in the next section.