1. Introduction 2. Basic Constructs and Data Types - University of ...

1. IntroductionComputer Systems: Hardware and Software (OS, Compilers, Application SW)Memory in Computer Systems: used for storing program binaries as well as basic andadvanced data typesProgramming Languages (High level, portable, i.e. machine independent) Syntax andSemanticsProgram CompilationA Simple C++ Program – Compilation and Execution – CLI vs GUIErrors in Programs: Compile time errors (Syntax errors) and Run time errors (logical errors)Algorithm – a step by step procedure for solving a computational problem. Later on in thecourse, we will be studying algorithms used in numerical methods and will implement someof these algorithms using C++ .2. Basic Constructs and Data TypesIn this chapter we review the basics of C++: keywords, variable declaration, initializationand assignment, basic data types, arithmetic and logical operators, operator precedence(BEDMAS). We conclude the chapter with a program to compute the volume of a cylinder.We assume that the user of the program will input radius r and height h of the cylinder.C++ keywords are words that are reserved for the C++ programming language. We cannotuse them as variable names (a.k.a. identifiers). Examples of C++ keywords are if, then, else,for, while, do, etc. The complete list of C++ keywords is available from if needed.Variables hold different data values and results in a C++ program. We need to declarevariables, initialize them if needed and only then use them in a C++ program. When variablesare declared, they must be a a specific data type. Two most common data types in C++ areint and float. When variables are declared, the compiler reserves memory space for storingthe value assigned to these variables. e.g. int x, y, z; float m, n;A const keyword applied to a variable forces the variable value to be fixed. For example ifwe declare: const float pi = 3.141594, then we try to assign pi = 5.2, then we will get acompile time error.© 2011 Mohammed A. S. Khalid

The fundamental data types available in C++ are: char, short, int, long, bool, float, double,long double and wchar_t. The number of bytes used for each data type depends on thecompiler and the CPU used. The operator sizeof can be used to obtain the number of bytesused for each data type for a specific compiler and CPU.The assignment operator “=” is used for assigning a value to a variable. This value can be anumber or the result of an arithmetic expression. For example:int x, y, x; int p; x = 20; y = 30; p = (x*x) +y;C++ provides a large number of arithmetic, logical, relational and other types of operators.Initially we will study only relatively simple operators. We will introduce more complexoperators later as needed. Commonly used operators are: +, -, *, / (arithmetic), !, &&, ||(logical), ==, !=, >, =,

3. Program Flow Control andIterationsThe if statement and the use of relational and logical operators; nested if and switch statements;handling abnormal exits from program; for and while statements.3.1What are the resulting values of k, l and m after the following C++ code is executed?int k = 7, l, m; l = k++; m = ++k; k *= m;3.2What is the resulting value of k, after the following C++ code is executed?int k = 7if (k < 5)k++;elsek--;3.3Determine the value of c after the following C++ code is executed. Briefly describe how you gotthe answer.main(){int a, b, c = 0;for (a=1; a

Program to illustrate scope of variables#include using namespace std;int w = 10, x = 5; // defined throughout this file and can be used in any functionmain(){int y = 2, z = 4; // defined only in main functioncout

For larger array sizes, we can use for loop to initialize array elements with a constant value.int b[100] ;for(int i=0; i

passed. Arrays are always passed by reference. CBR is also useful if the function needs to updatemore than one variable in the calling program. Examples of programs using CBV and CBR aregiven in sample programs set2.A structure in C++ allows us to create user defined variables types that can include ints, floats,doubles and even other structures. This is very useful in representing data used in many realworld computing tasks. For example, consider a structure that is used to represent a complexnumber. The idea of structure can be extended to define a class that forms the basis for objectoriented programming. We will cover classes in detail later.struct complex{double real;double imag;}complex a;a.real = 10.5;a.imag = 2.3; //a now represents the complex number (10.5 + 2.3i)Pointer variables are used to store address of other variables. A pointer can point to only onedata type or user defined variable type. For example a pointer to int must be different from apointer to float. We can have a pointer to a pointer as well. For example consider the programgiven below.main(){int x;int *y; // y is declared as a pointer to an integerint **z; // z is declared as a pointer to a pointerx = 25; // x is now 25y = &x; // &x means address of x, y now points to x*y = 15; // x is now 15z = &y;**z = 5; // x is now 5}For more detailed explanation of pointers, see Bijan’s presentation on pointers.When we declare an array of fixed size, the compiler reserves a fixed number of memorylocations for the array. For example, consider the following declaration:int array1[100];This will reserve 100 x 4 bytes of memory in the computer to store this array. We are assumingthat each int needs 4 bytes. If the program uses only a few elements of array1 the rest of thespace is wasted. This is an example of static memory allocation. Here we specify the array sizeat compile time.© 2011 Mohammed A. S. Khalid

In many applications, the memory requirements are not known until program run time. Forexample, consider a program that creates and stores class lists for all the courses being offered ina University for a particular term. The number of students in each course may vary from lessthan 10 to more than 200. For such applications, it will be wasteful to reserve memory at compiletime based on the largest values needed. This is where dynamic memory allocation is useful. Itallows us to reserve memory at run time. The following example illustrates dynamic memoryallocation in C++.int *parray; int asize;cout asize;parray = new int[asize]; // the new operator allocates memory to store// “asize” integers. parray is initialized to point to start of the arrayIn many Object oriented programming (OOP) is a methodology that uses objects and theirinteractions to efficiently design and implement computer programs for complex real worldapplications. OOP has many advantages such as modular programs, information hiding,inheritance, polymorphism, ease of software reuse, etc. Classes and objects form the basis ofOOP. A class can be thought of as a complicated user defined data type that may consist offundamental data types, structures and even other classes. In addition to data types, the functionsfor accessing and manipulating data types are also defined in a class. This is what differentiates aclass from a structure. That is also the reason why structures are rarely used in C++. An objectcan be thought of as an instance of a class, i.e. a physical manifestation of a class in computermemory. Classes enable modular program development and software reuse. They enable easiertesting of software by localizing the errors in specific modules which makes it easier to find andfix program errors. They also help in the design and implementation of complex softwaresystems by providing features for information hiding. This means that the implementation offunctions in a class is hidden from the user of the class. Any changes done in the functions of theclass will not adversely affect users of the class.A class consists of data members and member functions. Consider a simple class given below forrepresenting the time of day.class time_of_day{private:int hrs, mins, secs;public:time_of_day();time_of_day(int hrs, int min, int sec);int get_hrs();int get_mins();int get_secs();void print();};© 2011 Mohammed A. S. Khalid

Data members in this class are hrs, mins and secs. The keyword private indicates that thesevariables (data members) can be changed only by member functions of this class. Note that alldata members are in a class are private by default. We are just using the keyword private toemphasize this point. There are six member functions defined for this class. The keyword publicused for member functions indicates that these functions can be called from code outside theclass. The first two functions are constructors. Their names must be identical to class names andthey do not have a return type, not even void. Note that the two constructor functions haveidentical names. This is an example of function overloading. Two or more functions have thesame name but are differentiated by the number of function parameters used.It is better to list the data members and member function prototypes in the class definition as aseparate header file. Note that when we write the code for implementing member functionsoutside of class definition, we need to use the scope resolution operator “::”. The code for thetwo constructor functions is given below. There is a check in the code to make sure that valuespassed for hours (0 to 23), minutes (0 to 59) and seconds (0 to 59) are valid. Assume that if novalues are specified, the data members will be set to 0.time_of_day :: time_of_day() : hrs(0), mins(0), secs(0) {}time_of_day :: time_of_day (int h, int m, int s){if(h >= 0 && h < 23)hrs = h;elsecout

• There is more than one method for initializing a 1-D array• An array can be initialized using cout(b)List errors, if any, in each of the following statements. In case of error, briefly describe the errorand write the correct statement.• int a = {11, 22}, b[33];• float c[3] = {11.0, 22.0, 33.0, 44.0};• d[4] = {11, 22, 33, 44};• int a[3] /11, 22, 33/;5.3Assuming that an integer variable is represented using four bytes, what are the values ofvariables a, b and c after the following code is executed?int a, b, c; int mtrx [5][5];a = sizeof (mtrx); b = sizeof (mtrx[1]);c = sizeof (mtrx[1][1]);5.4What is the value of the variables a, (*k) and (**m) after the following code is executed?int a, b, c, *k, **m;a = 10; b = ++a; c = b++;k = &b; m = &k;5.5Give the C++ code for all the member functions in the class time_of_day that was discussedearlier in this chapter.5.6Give the C++ code for defining a class called employee. The data members in this class are name(string), address (string), salary (double) and id_num (long int). Write suitable and appropriateconstructors and member functions that can be used for this class. Write a main program thatcreates objects for this class and prints out information about those objects.© 2011 Mohammed A. S. Khalid