A program in C++
is a collection of one or more functions. This program has only one function named main. The function main is a required function in all programs. If there are several functions in a program, each function carries out a different task. The main function will call other functions into action.

Description of the program:
Lines beginning with /* and ending with */ are comments, C++ ignores these lines. These comments are used for internal documentation. // may be used for commenting one line.

Preprocessor library:
C language is a small language and does not have inherent input/output support. Input/output support is provided by modules (library). This program outputs one line of text to the monitor. The monitor is the standard output device and the keyboard is the standard input device. A pound sign # indicates that the remainder of that line is an instruction (directive) to the compiler. #include <iostream.h> tells the compiler to add the code found in that file to the beginning of this program. This code handles all character stream inputs and outputs. Without this you cannot read from the keyboard or display anything to the monitor.

A function:
int main () is a function. A function receives one or more parameters (arguments) from the calling module and returns none or one result to the calling module. The word int before the function name (main) indicates that the function will return an integer to the calling module. The calling module of the main is the operating system. This program returns a zero to the operating system, indicating normal execution. The () after the function name indicates that this function does not receive any parameters from the calling module. Later we will see variations to this.

Begin and End of a block:
The beginning of a body or compound statement is indicated by { and the ending is indicated by }.

Statement separator: A statement is separated from another statement by placing a semicolon between them. End of the line does not indicate end of a statement.

cout and cin:
cout displays (prints) to an output device such as a monitor, and cin receives input from an input device such as a keyboard. The << or >> indicates the direction of flow of the data. In this program, "See mom! I wrote my first C++ program\n, is the data (in this case the data is a literal) that flows into the output device. Notice that the string literal is enclosed in double quotes. The last two characters in the literal \n makes the cursor to go to a new line. The backslash is used as a symbol for escape. An escape sequence is used to control output devices. We will see additional escape sequences later.

Modification of the program:
Adding one line to the program stops the screen for you press an enter key.

Program 1-1A

Arithmetic in C++
When we write code in C++ to do calculations, it is important to remember that results of integer and integer calculations may be different than real and real calculations. We also need to know how mixed number calculations will be carried out. C++ will allow you to assign a number with decimal to an integer, however, the fractional part will be discarded.

If l=6.5 and m= 3.5 then l+m should be 10, why is it 9? We assigned these numbers to integer variables, which discards the fractional part leaving 6 and 3, which give a total of 9.
How about 10/9 yielding 3? This is called integer division.

The next problem 10 % 3 gives a result of 1, which is the remainder of the integer division (also known as the modulus).

In the next problem even though we assigned the result of 10/3 to a real variable (a), the variable only received the result of an integer division. The result of 10.0/3.0 is 3.333333; here both numbers are real numbers (float).

However the last problem 10.0/3 also gives 3.33333, why? In a mixed operation like this the integer is converted to float first, then the operation is carried out.

The terminology given at the beginning of this chapter is very important. You must learn it thoroughly. Make q-cards and memorize the terms.
Write this program over and over again until you do not have to look at the notes. You should not continue to the next chapter until you mastered this chapter thoroughly. This homework may appear surprisingly easy to you. Don't be fooled. Many students do not finish the course because they do not spend much time with the first two chapters.
Write a program to determine the number of thousands, hundreds, tens, and ones in a given number. Hint: use integer division and modulus. Example of a program run:

In 8532 there are
8 thousands
5 hundreds
3 tens
2 ones.

You are required to submit hard copies of all programs and program runs for every assignment given to you. You are required to submit structure charts and pseudocodes aswell. This addendum Chapter 1 describes how to send the output to a text file which can be printed from any program or directly from DOS.

Suppose you created a text file called carpet.txt from a program, this file then can be printed by opening it under Word, WordPerfect, or any other program you like and then printing from it. You can also print it by going to DOS prompt and typing the following: type carpet.txt > prn

Program OneA_1.

/******************************************************** Printing to a file By Dr. John Abraham Created for 1380 students Instructional objective: create print file One_2.txt ********************************************************/ #include <iostream.h> #include <fstream.h> //to handle files int main () { int i,j,k,l, m,n; float a,b,c; ofstream outfile; //output file stream handle is outfile outfile.open("a:One_2.txt"); //assign a DOS name to the handle //creates a file called One_2.txt in floppy drive A: //integer operations cout << "INTEGER OPERATIONS\n \n"; i = 6 + 3; l = 6.5; m = 3.5; j = l + m; k = 10 /3; n = 10 % 3; cout << "6 + 3 = " << i << "\n"; cout << "l = 6.5, m = 3.5 --------->l + m = " << j << "\n"; cout << "10 / 3 = " << k << "\n"; cout << "10 % 3 = " << n << "\n"; outfile << "6 + 3 = " << i << "\n"; outfile << "l = 6.5, m = 3.5 --------->l + m = " << j << "\n"; outfile << "10 / 3 = " << k << "\n"; outfile << "10 % 3 = " << n << "\n"; //real and mixed operations cout << "\nREAL AND MIXED OPERATIONS \n \n"; outfile << "\nREAL AND MIXED OPERATIONS \n \n"; a = 10 / 3; b = 10.0 / 3.0; c = 10.0 /3; cout << "10 / 3 = " << a << "\n"; cout << "10.0 / 3.0 = " << b << "\n"; cout << "10.0 / 3 = " << c << "\n"; outfile << "10 / 3 = " << a << "\n"; outfile << "10.0 / 3.0 = " << b << "\n"; outfile << "10.0 / 3 = " << c << "\n"; outfile.close(); getchar(); return 0; }

In order to create a textfile follow these steps:

• Required preprocessor directive: #include <fstream.h>
  
• Give a file handle such as outfile, printfile, textfile, or anything you like.
  Now on the file will be referred to using this name in the program.
  
• Assign this handle to an actual DOS file name. DOS file names are 8 character long, a dot, and 3 character extension. You may include the drive letter and path in front of the file name. For example: C:\mydocuments\cprograms\printfiles\carpet.txt
  
• Place any character stream you want in this file by using the << flow director. The easiest way to do this is to make copies of every cout lines in the program and change the cout to the file handle name. See example Program OneA_1.
  
• Close the file.

To print the textfile created by this program, follow these steps:

• Open Notepad from Startą Programsą Accessories
  
• Open the file you created
  
• From file option, choose print