Computer programming Engr. Otitigbe Obadiah Oghoerore Alegbe Profesor de Sistemas Universidad Nacional de Lanus Buenos Aires – Argentina

we can define a variable as a portion of memory to store a determined value. Each variable needs an identifier that distinguishes it from the others. For example, in the previous code the variable identifiers were a, b and result, but we could have called the variables any names we wanted to invent, as long as they were valid identifiers. Fundamental data types When programming, we store the variables in our computer's memory, but the computer has to know what kind of data we want to store in them, since it is not going to occupy the same amount of memory to store a simple number than to store a single letter or a large number, and they are not going to be interpreted the same way. The memory in our computers is organized in bytes. A byte is the minimum amount of memory that we can manage in C++. A byte can store a relatively small amount of data: one single character or a small integer (generally an integer between 0 and 255). In addition, the computer can manipulate more complex data types that come from grouping several bytes, such as long numbers or non-integer numbers. Next you have a summary of the basic fundamental data types in C++, as well as the range of values that can be represented with each one:

Below are just estimate values, In some Operating system or IDE, there may be different

Declaration of variables In order to use a variable in C++, we must first declare it specifying which data type we want it to be. The syntax to declare a new variable is to write the specifier of the desired data type (like int, bool, float...) followed by a valid variable identifier. For example: 1 2 int a; float mynumber; These are two valid declarations of variables. The first one declares a variable of type int with the identifier a. The second one declares a variable of type float with the identifier mynumber. Once declared, the variables a and mynumber can be used within the rest of their scope in the program. If you are going to declare more than one variable of the same type, you can declare all of them in a single statement by separating their identifiers with commas. For example: int a, b, c; This declares three variables (a, b and c), all of them of type int, and has exactly the same meaning as: int a; int b; int c; We are going to write a program that will print the value of a data on the computer screen. To do that, we must first declare a variable to hold the data, then we give value to it or initialize the data after which we shall print the data on the computer screen. For us to put the data on the screen we need a function form the library called printf. Printf has a convention and we format it dependint on the variable. When we want to put and integer value on the screen we arrange the inromation within printf for printf to interprete it. Supossing we want to print the number of student in a class, by logic the number bust be less that 250, thus we shal use short int. So we must declare a variable of short int or int and initialize it with the number of student. Int numStudents; numStudents = 50; Note we initialize the value. With printf we ´put the value on the screen. Printf(“%d”,numStudents); Let us see how it is done inside DevC++. Let us create a new project and then write the code. We shall have the following:

Declare a variable to hold number of students, initialize it and print it on the screen #include using namespace std; int main(int argc, char *argv[]) { int numStudents; numStudents = 50; printf("%d",numStudents); system("PAUSE"); return EXIT_SUCCESS; }

Suposing we want to print a salary which has decimal number, in this case we use float. We declare a variable of float type and initialize it. Float f_Salary; F_Salary = ; Printf(“%f”,f_Salary) #include using namespace std; int main(int argc, char *argv[]) { float f_Salary;; f_Salary = printf("%f",f_Salary); system("PAUSE"); return EXIT_SUCCESS; }