Cmpt 128 introduction to computing science for engineering students
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CMPT 128: Introduction to Computing Science for Engineering Students. Introduction to the basic components of C and C++ programs. Introduction. Computer program : an ordered sequence of instructions whose objective is to accomplish a task .

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Cmpt 128 introduction to computing science for engineering students

CMPT 128: Introduction to Computing Science for Engineering Students

Introduction to the basic components of

C and C++ programs


Introduction
Introduction

  • Computer program:an ordered sequence of instructions whose objective is to accomplish a task.

  • Programming:process of planning and creating a program

  • Programming Language: a set of symbols, special words (semantics), and rules for using those symbols and special words (syntax) to create statements to implement the ordered sequence of instructions to accomplish a task


Problem solving
Problem solving

  • When we try to solve a problem using programming we should always begin by breaking the problem into parts.

    • Each part describes a process that solves part of the problem (or an object that is part of the problem)

    • Each part can be implemented as a function within a program to solve the problem (or a class)


Programs and libraries
Programs and Libraries

  • Programs are divided into smaller modules called functions.

  • Functions can

    • be separately tested and reused by many programs

    • Use other functions

    • Be used by other functions

    • Become part of libraries


Programs
Programs

  • Every program has a main function.

    • The main function controls the highest level of abstraction of the program.

    • The main function may call other functions to complete lower level tasks (like evaluating an exponential)

    • Many commonly needed functions are supplied in libraries as part of the C and or C++ language, some less commonly needed functions are available as additional add on libraries


C and c
C and C++

  • C is a subset of C++

    • C codes will run inside a C++ application

    • All C libraries are available in C++

  • C++ contains many extensions of C

    • C++ is object oriented and allows classes

    • C++ libraries that are based on classes cannot be used in C


The components of a program
The Components of a Program

  • Each C or C++ program includes a series of functions or program units.

    • Every C++ application program includes a main function, sometimes called a main program

    • There may be other functions used by the main program.

      • Functions from C and C++ libraries

      • Functions written by the user

  • For your first programs we will illustrate only a main function and some functions from libraries


Hello world your first c program
Hello World: your first C++ program

// My first C++ program

// make the computer print Hello world

// connect to any necessary libraries

#include <iostream>

// required, will be explained later in the course

using namespace std;

// the main function, implements the algorithm to solve the problem

// the main function may use functions input an output functions from the iostream

// library. cout is one of these functions.

int main ( )

{

cout << "Hello, world!“ << endl;

return 0;

}


Hello world your first c program1
Hello World: your first C program

/* My first C++ program */

/* make the computer print Hello world */

/* connect to any necessary libraries */

#include <stdio.h>

/* the main function, implements the algorithm to solve the problem

the main function may use functions input an output functions from the iostream

library. cout is one of these functions. */

int main ( )

{

fprintf( stdout, “Hello World \n” );

return 0;

}


Comments
Comments

  • Comments are essential to clearly explain the purpose of your code and the methods of implementation used

    • When you use another programmer’s code

    • When another programmer tries to use your code

    • When you try to use your own code after months or years

  • Comments make it is much easier to figure out how things work in existing code.

  • Comments are not “executed”


Good comments
Good Comments

  • Do give additional information not obvious from the code

    // This program calculates the first 20 primes

  • Do not translate code into English

    // Add A to B (BAD COMMENT)

    C = A+B


C comments syntax
C++ Comments: syntax

  • Comments begin // and end at the end of the line

  • Comments can appear on their own line

    • // This is a comment

  • Comments can appear on the same line as an expression

    • A = b + c; // add b to c and store the result in A


Hello world your first program
Hello World: your first program

// My first C++ program

// make the computer print the string “Hello world”

// connect to any necessary libraries

#include <iostream>

using namespace std;

// the main function, implements the algorithm to solve the problem

// the main function may use functions from included libraries

int main ( )

{

cout << "Hello, world!“ << endl; // Prints Hello world

return 0;

}


C comments syntax1
C Comments: syntax

  • Comments begin /* and end */

  • Comments can appear on their own line or on their own block of lines

    • /* This is a C comment

      it continues until it is closed */

  • Comments can appear on the same line as an expression

    • A = b + c; /* add b to c, put the result in A */


Hello world your first c program2
Hello World: your first C program

/* My first C program */

/* make the computer print Hello world */

/* connect to any necessary libraries */

#include <stdio.h>

/* the main function, implements the algorithm to solve the problem

the main function may use functions input an output functions from the iostream

library. cout is one of these functions. */

int main ( )

{

fprintf( stdout, “Hello World \n” );

return 0;

}


Libraries
Libraries

  • A main function, or any other function may wish to use functions in the built in libraries of the C or C++ language or in user developed or application libraries

  • To use such functions our program must indicate that the libraries are being used and provide a way to access those functions


Hello world c
Hello World: C++

// My first C++ program

// make the computer print the string “Hello world”

// connect to any necessary libraries

#include <iostream> // iostream is a library used to read and write

using namespace std;

// the main function, implements the algorithm to solve the problem

// the main function may use functions from included libraries

// the iostream library includes read and write functions like cout

int main ( )

{

cout << "Hello, world!“ << endl; // Prints Hello world

return 0;

}


Important
Important

  • In our first C++ program we are using the iostream library.

    • This library is used to read from the keyboard and write to the screen

    • Any C++ program that reads or writes information should include the iostream library

  • Later we will look at the details of what we can do with this library. (much more)


Hello world your first c program3
Hello World: your first C program

/* My first C program */

/* make the computer print Hello world */

/* connect to any necessary libraries */

#include <stdio.h>

/* the main function, implements the algorithm to solve the problem

the main function may use functions input an output functions from the iostream

library. cout is one of these functions. */

int main ( )

{

fprintf( stdout, “Hello World \n” );

return 0;

}


Important1
Important

  • In our first C program we are using the stdiolibrary.

    • This library is used to read from the keyboard and write to the screen

    • Any C program must use the stdio library

    • Any C++ program may use either the stdiolibrary or the iostream library


Example standard libraries c c
Example: Standard Libraries (C,C++_)

  • #include <stdio.h>

    • The # at the beginning of the line indicates that the command is for the C++ preprocessor (a preprocessor directive)

    • The Cor C++preprocessor puts the contents of the file stdio.hinto your program instead of the line of code above then passes the resulting code to the compiler

    • If the preprocessor directive to include the library is not part of your program, your program will not be able to use the functions in the library


Using libraries in c and c
Using Libraries in C and C++

  • A C or C++ program that wants to use libraries starts with one or more include directives

    • #include <Library_Reference>

    • #include “Library_Reference” //(details later)

  • Here Library_Referenceindicates the name of a file containing a list of all the functions in the library.


Syntax of include directive
Syntax of include directive

#include <Library_Reference>

#include “Library_Reference”

  • “ “ indicates that the files location should be completely specified by the programmer.

  • < > indicates that the file is part of the C or C++ language itself and can be located by the preprocessor, compiler and linker without programmer intervention.


Hello world c1
Hello World: C++

// My first C++ program

// make the computer print the string “Hello world”

// connect to any necessary libraries

#include <iostream> // iostream is a library used to read and write

using namespace std; // not needed for C

// the main function, implements the algorithm to solve the problem

// the main function may use functions from included libraries

// the iostream library includes read and write functions like cout

int main ( )

{

cout << "Hello, world!“ << endl; // Prints Hello world

}


Name spaces
Name Spaces

using namespace std

  • Indicates you wish to use the standard namespace

  • In large advanced programs it is possible that you want to use additional namespaces to prevent naming conflicts.

  • For this course you will always use the standard namespace and you will always have this line in your programs


Hello world c2
Hello World: C++

// My first C++ program

// make the computer print the string “Hello world”

// connect to any necessary libraries

#include <iostream> // iostream is a library used to read and write

using namespace std;

// the main function, implements the algorithm to solve the problem

// the main function may use functions from included libraries

// the iostream library includes read and write functions like cout

int main ( )

{

cout << "Hello, world!“ << endl; // Prints Hello world

return 0;

}


Creating a c or c main function
Creating a C or C++ main function

int main ( )

{

Body of the main function

return 0;

}

  • The start of the main method is indicated by the statement int main ( )

  • The body of the main method (the code that accomplishes the task of the main method) is enclosed in { }.

  • The convention used in this course in to put each of the { } on a separate line.


Hello world c3
Hello World: C++

// My first C++ program

// make the computer print the string “Hello world”

// connect to any necessary libraries

#include <iostream> // iostream is a library used to read and write

using namespace std;

// the main function, implements the algorithm to solve the problem

// the main function may use functions from included libraries

// the iostream library includes read and write functions like cout

int main ( )

{

cout << "Hello, world!“ << endl; // Prints Hello world

return 0;

}


Body of the c program
Body of the C++ program

  • For our first program the body consists of a single line of code

    cout << "Hello, world!“ << endl;

  • cout prints to the screen

  • Everything inside the “ “ is printed

  • endl means move to the start of the next line before printing anything else


Simple examples of c cout
Simple examples of C++ cout

  • Print the word OUCH to the screen

    cout << “OUCH”;

  • Move to the beginning of a new line then print the sum of 6.5 and 3.5 to the screen

    cout << endl << 6.5 + 3.5;


Hello world your first c program4
Hello World: your first C program

/* My first C program */

/* make the computer print Hello world */

/* connect to any necessary libraries */

#include <stdio.h>

/* the main function, implements the algorithm to solve the problem

the main function may use functions input an output functions from the iostream

library. cout is one of these functions. */

int main ( )

{

fprintf( stdout, “Hello World \n” );

return 0;

}


Body of the c program1
Body of the C program

  • For our first program the body consists of a single line of code

    fprintf( stdout, “Hello World \n” );

  • fprintfprints to the screen

  • Everything inside the “ “ is printed except control characters preceeded by \

  • \nmeans move to the start of the next line before printing anything else


Simple examples of c fprintf
Simple examples of C fprintf

  • Print the word OUCH to the screen

    fprintf( stdout, “OUCH”);

  • Move to the beginning of a new line then print the sum of 6.5 and 3.5 to the screen

    fprintf( stdout, “\n %f”, 6.5 + 3.5);


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