Example program ------> TRIVIAL.C
The best way to get started with C is to actually study a program, so load the file named TRIVIAL.C and display it on the monitor. You are looking at the simplest possible C program. There is no way to simplify this program or to leave anything out. Unfortunately, the program doesn't do anything.The word main is very important, and must appear once, and only once in every C program. This is the point where execution is begun when the program is run. We will see later that this does not have to be the first statement in the program but it must exist as the entry point. Following the main program name is a pair of parentheses which are an indication to the compiler that this is a function. We will cover exactly what a function is in due time. For now, I suggest that you simply include the pair of parentheses. The two curly brackets in lines 2 and 3, properly called braces, are used to define the limits of the program itself. The actual program statements go between the two braces and in this case, there are no statements because the program does absolutely nothing. You can compile and run this program, but since it has no executable statements, it does nothing. Keep in mind, however, that it is a valid C program. When you compile this program, you may get a warning. You can ignore the warning and we
will discuss it later in this tutorial, or you can modify the program so that it appears as follows;
int main()
{
return 0;
}
This modified program must compile on any good C compiler since it conforms to the ANSI-C standard.
We will explain the difference in these two programs later in this tutorial.
A PROGRAM THAT DOES SOMETHING
Example program ------> WRTSOME.C
For a much more interesting program, load the program named WRTSOME.C and display it on your monitor. It is the same as the previous program except that it has one executable statement between the braces plus the obligatory return statement.
The executable statement is a call to a function supplied as a part of your C library. Once again, we will not worry about what a function is, but only how to use this one named printf(). In order to output text to the monitor, the desired text is put within the function parentheses and bounded by quotation marks. The end result is that whatever text is included between the quotation marks will be displayed on the monitor when the program is run.Notice the semi-colon at the end of line 5. C uses a semi-colon as a statement terminator, so the semi-colon is required as a signal to the compiler that this line is complete. This program is also executable, so you can compile and run it to see if it does what you think it should. It should cause the text between the quotation marks to appear on the monitor when you execute it.You can ignore the statements in lines 1 and 7 in this program and similar statements in each of the remaining programs in this chapter. These will be fully described later in this tutorial. We will also define why the word int is used at the begining of line 3. We have a few preliminary topics to cover before we get to these items.
ANOTHER PROGRAM WITH MORE OUTPUT
Example program ------> WRTMORE.C
Load the program WRTMORE.C and display it on your monitor for an example with more output and another small but important concept. You will see that there are four executable statements in this program, each one being a call to the function printf(). The top line will be executed first, then the next, and so on, until the fourth line is complete. The statements are executed sequentially from top to bottom.Notice the funny character near the end of the first line, namely the backslash. The backslash is used in the printf() statement to indicate that a special control character is following. In this case, the "n" indicates that a newline is requested. This is an indication to return the cursor to the left side of the monitor and move down one line. Any place within printed text that you desire, you can put a newline character to start a new line. You could even put it in the middle of a word and split the word between two lines.
A complete description of this program is now possible. The first printf() outputs a line of text andreturns the carriage. (Of course, there is no carriage, but the cursor is moved to the next line on the monitor. The terminology carries over from the days of teletypes.) The second printf() outputs a line of text but does not return the carriage so that the third line is appended to the end of the second, then followed by two carriage returns, resulting in a blank line. Finally the fourth printf() outputs a line followed by a carriage return and the program is complete.
After compiling and executing WRTMORE.C, the following text should be displayed on your monitor;
This is a line of text to output.
And this is another line of text.
This is a third line.
Compile and execute this program to see if it gives you this output. It would be a good idea at this time for you to experiment by adding additional lines of printout to see if you understand how the statements really work. Add a few carriage returns in the middle of a line to prove to yourself that it works as stated, then compile and execute the modified program. The more you modify and compile the example programs included with this tutorial, the more you will learn as you work your way through it.
The best way to get started with C is to actually study a program, so load the file named TRIVIAL.C and display it on the monitor. You are looking at the simplest possible C program. There is no way to simplify this program or to leave anything out. Unfortunately, the program doesn't do anything.The word main is very important, and must appear once, and only once in every C program. This is the point where execution is begun when the program is run. We will see later that this does not have to be the first statement in the program but it must exist as the entry point. Following the main program name is a pair of parentheses which are an indication to the compiler that this is a function. We will cover exactly what a function is in due time. For now, I suggest that you simply include the pair of parentheses. The two curly brackets in lines 2 and 3, properly called braces, are used to define the limits of the program itself. The actual program statements go between the two braces and in this case, there are no statements because the program does absolutely nothing. You can compile and run this program, but since it has no executable statements, it does nothing. Keep in mind, however, that it is a valid C program. When you compile this program, you may get a warning. You can ignore the warning and we
will discuss it later in this tutorial, or you can modify the program so that it appears as follows;
int main()
{
return 0;
}
This modified program must compile on any good C compiler since it conforms to the ANSI-C standard.
We will explain the difference in these two programs later in this tutorial.
A PROGRAM THAT DOES SOMETHING
Example program ------> WRTSOME.C
For a much more interesting program, load the program named WRTSOME.C and display it on your monitor. It is the same as the previous program except that it has one executable statement between the braces plus the obligatory return statement.
The executable statement is a call to a function supplied as a part of your C library. Once again, we will not worry about what a function is, but only how to use this one named printf(). In order to output text to the monitor, the desired text is put within the function parentheses and bounded by quotation marks. The end result is that whatever text is included between the quotation marks will be displayed on the monitor when the program is run.Notice the semi-colon at the end of line 5. C uses a semi-colon as a statement terminator, so the semi-colon is required as a signal to the compiler that this line is complete. This program is also executable, so you can compile and run it to see if it does what you think it should. It should cause the text between the quotation marks to appear on the monitor when you execute it.You can ignore the statements in lines 1 and 7 in this program and similar statements in each of the remaining programs in this chapter. These will be fully described later in this tutorial. We will also define why the word int is used at the begining of line 3. We have a few preliminary topics to cover before we get to these items.
ANOTHER PROGRAM WITH MORE OUTPUT
Example program ------> WRTMORE.C
Load the program WRTMORE.C and display it on your monitor for an example with more output and another small but important concept. You will see that there are four executable statements in this program, each one being a call to the function printf(). The top line will be executed first, then the next, and so on, until the fourth line is complete. The statements are executed sequentially from top to bottom.Notice the funny character near the end of the first line, namely the backslash. The backslash is used in the printf() statement to indicate that a special control character is following. In this case, the "n" indicates that a newline is requested. This is an indication to return the cursor to the left side of the monitor and move down one line. Any place within printed text that you desire, you can put a newline character to start a new line. You could even put it in the middle of a word and split the word between two lines.
A complete description of this program is now possible. The first printf() outputs a line of text andreturns the carriage. (Of course, there is no carriage, but the cursor is moved to the next line on the monitor. The terminology carries over from the days of teletypes.) The second printf() outputs a line of text but does not return the carriage so that the third line is appended to the end of the second, then followed by two carriage returns, resulting in a blank line. Finally the fourth printf() outputs a line followed by a carriage return and the program is complete.
After compiling and executing WRTMORE.C, the following text should be displayed on your monitor;
This is a line of text to output.
And this is another line of text.
This is a third line.
Compile and execute this program to see if it gives you this output. It would be a good idea at this time for you to experiment by adding additional lines of printout to see if you understand how the statements really work. Add a few carriage returns in the middle of a line to prove to yourself that it works as stated, then compile and execute the modified program. The more you modify and compile the example programs included with this tutorial, the more you will learn as you work your way through it.
No comments:
Post a Comment