Csc240 -lecture_3

CSC240
INTRODUCTION TO PROGRAMMING – I
Mr. Dilawar
Lecturer,
Department of Computer Science,
Jahan University
Kabul, Afghanistan.

Previous Lecture Outline
• Understanding the concept of flowcharts.
• Working with sequence, decision, repetition and case control
flowchart structures.
• Understanding algorithms.

Lecture Outline
• Introduction to C++ and other popular programming languages
• Historical development of C++
• Writing C++ program
• Structure of C++ program

Introduction to C++
• C++ is the advanced version of C language that is used for developing
computer programs.
• C++ is a powerful programming language that fully supports
• Procedural programming
• Object-oriented programming
• Data abstraction
• Generic programming

Other Popular Programming Languages

Historical Development of C++ Language
Programming Language Description
BCPL Language
Developed in 1967 by Martin Richards as a language for writing operating
systems and compilers for operating system.
B Language
Developed by Ken Thompson at Bell Laboratories. The early version of UNIX
operating system developed in 1970.
C Language
Developed by Dennish Ritche in 1972 by Bell Laboratories. It is available for
most computers and is hardware independent. Portable computer programs
can be created.
C++ Language
C++ is the extension of C developed by Bjarne Stroustrup in the early 1980s at
Bell Laboratories. It provides the capabilities of object-oriented programming.
Current versions of C++ such as Microsoft Visual C++ .NET and Borland C++ Builder.
We will follow the syntax and rules of turbo C++ version 3.0 and Borland C++ v5 for MS DOS environment.

Writing C++ Program
• C++ systems generally consist of three parts
• A program development environment
• The language
• C++ Standard Library
• C++ programs typically go through six phases
• Edit, Preprocess, Compile, Link, Load and Execute.

Writing C++ Program
• Phase 1 consists of editing a file with an editor program, normally
known simply as an editor.
• Type a C++ program (source code) using the editor.
• Make any necessary corrections.
• Save the program.
• C++ source code filenames often end with the .cpp, .cxx, .cc or .C extensions
(note that C is in uppercase) which indicate that a file contains C++ source
code.

Writing C++ Program
• Linux editors: vi and emacs.
• C++ software packages for Microsoft Windows such as Microsoft
Visual C++ (microsoft.com/express) have editors integrated into the
programming environment.
• You can also use a simple text editor, such as Notepad in Windows, to
write your C++ code.
• Integrated Development Environments (IDEs)
• Provide tools that support the software-development process, including
editors for writing and editing programs and debuggers for locating logic
errors—errors that cause programs to execute incorrectly.

Writing C++ Program
• Popular IDEs
• Microsoft® Visual Studio 2012 Express Edition
• Dev C++
• NetBeans
• Eclipse
• Apple’s Xcode
• CodeLite

Writing C++ Program
• In phase 2, you give the command to compile the program.
• A preprocessor program executes automatically before the compiler’s
translation phase begins (so we call preprocessing Phase 2 and compiling
Phase 3).
• The C++ preprocessor submits commands called preprocessing directives,
which indicate that certain manipulations are to be performed on the
program before compilation.
• These manipulations usually include other text files to be compiled, and
perform various text replacements.

Writing C++ Program
• In Phase 3, the compiler translates the C++ program into machine-
language code—also referred to as object code.

Writing C++ Program
• Phase 4 is called linking.
• The object code produced by the C++ compiler typically contains “holes” due
to some missing parts.
• A linker links the object code with the code for the missing functions to
produce an executable program.
• If the program compiles and links correctly, an executable image is produced.

Writing C++ Program
• Phase 5 is called loading.
• Before a program can be executed, it must first be placed in memory.
• This is done by the loader, which takes the executable image from disk and
transfers it to memory.
• Additional components from shared libraries that support the program are
also loaded.

Writing C++ Program
• Phase 6: Execution
• Finally, the computer, under the control of its CPU, executes the program
one instruction at a time.
• Some modern computer architectures can execute several instructions in
parallel.

Writing C++ Program
• Problems That May Occur at Execution Time
• Programs might not work on the first try.
• Each of the preceding phases can fail because of various errors that we’ll
discuss throughout this course.
• If this occurred, you’d have to return to the edit phase, make the necessary
corrections and proceed through the remaining phases again to determine
that the corrections fixed the problem(s).
• There is also a standard error stream referred to as cerr. The cerr stream is
used for displaying error messages.

Structure of C++ Program
• Preprocessor Directives
• Header Files
• main() function
• Body of main() function
• Statements

• The instructions that are given to the compiler before the beginning
of the actual program are called preprocessor directives.
• Also known as compiler directives.
• The preprocessor directives consist of instructions for the compiler.
• The compiler adds special instructions or code from these directives into the
program at the time of compilation.
• It starts with a # (HASH) or (SHARP) and the keyword include or define.
• They are used to include header files.

• Header files in C++ are source files that
contains definitions of library
functions/objects.
• A header is added if function/object defined
in it is to be used in the program.
• For example, the header file iostream.h has
the definitions of different built-in
input/output functions. To include the
header file into the C++ source code we
normally write:
#include<iostream>
int main()
{
…………
…………
return 0;
}

• The C++ program is typically consist
of at least one function called
main() function.
• When C++ program starts execution,
main() is the first program that is
executed.
• The keyword int to the left of main()
indicates that main() “returns” an
integer (whole number) value.
#include<iostream>
int main()
{
…………
…………
return 0;
}

• Each function may or may not
return a value back.
• The function contains body in which
duties of the function is placed.
#include<iostream>
int main()
{
…………
…………
return 0;
}

• A statement instructs the computer to
perform an action.
• Together, the quotation marks and the
characters between them are called a
string, a character string or a string
literal.
• Most C++ statements end with a
semicolon (;), also known as the
statement terminator.
• C++ is a case-sensitive language.
#include<iostream>
int main()
{
…………
…………
return 0;
}

• You use blank lines, space characters and tab characters (i.e., “tabs”)
to make programs easier to read.
• Together, these characters are known as white space.
• White-space characters are normally ignored by the compiler.

• Comments can be used for
understanding the source
code.
• Single-line (//…………..)
comment vs multi-line
(/*……..*/) comment.
//sample program
#include<iostream>
int main()
{
…………
…………
return 0;
}

Example
#include<iostream> //Preprocessor Directive
using namespace std;
int main(){ //main() function
cout<<“Hello world”; //statements
return 0;
}

Escape Characters
• They can be used as a separate characters or embedded in string
constant.

Summery
• Introduction to C++ and other popular programming languages
• Historical development of C++
• Writing C++ program
• Structure of C++ program

Csc240 -lecture_3

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