an overview of computers and programming languages_ch01

C++ Programming: Program Design IncludingData Structures, Fifth Edition

Chapter 1: An Overview of Computers and Programming

Languages

C++ Programming: Program Design Including Data Structures, Fifth Edition 2

Mohd Rosmadi Mokhtar

[email protected]

G-3-28

mailto:[email protected]

ObjectivesIn this chapter, you will:

• Learn about different types of computers

• Explore the hardware and software components of a computer system

• Learn about the language of a computer

• Learn about the evolution of programming languages

• Examine high-level programming languages• Discover what a compiler is and what it does• Examine a C++ program• Explore how a C++ program is processed


Introduction

• Without software, the computer is useless• Software developed with programming

languages– C++ is a programming language

• C++ suited for a wide variety of programming tasks

• Before programming, it is useful to understand terminology and computer components


A Brief Overview of the History of Computers

• Early calculation devices

– Abacus, Pascaline

• (only addition and subtraction)

– Leibniz device (addition, subtraction, multiplication, division)

– Babbage machines: difference and analytic engines

– Hollerith machine. Run on electricity and can store data. (IBM)


Leibniz deviceHollerith machine Leibniz device

A Brief Overview of the History of Computers (cont'd.)

• Early computer-like machines– Mark I. 52 feet long, 50 tons weight, and 750,000 parts – ENIAC. Electrical Numerical Integrator And Calculator– Von Neumann architecture. Base for Today computer design:

Arithmetic logic unit, control unit, memory, input/output devices– UNIVAC. UNIVersal Automatic Computer– In1956, Transistors and microprocessors invented

C++ Programming: Program Design Including Data Structures, Fifth Edition 6Mark IENIACUNIVAC


A Brief Overview of the History of Computers (cont'd.)

• Early computer-like machines– In 1970, microprocessor, an entire CPU on a single chip, was

invited.– 1977, first Apple computer was built.– 1981, IBM introduced its personal computer.


http://en.wikipedia.org/wiki/File:Intel_4004.jpg

Elements of a Computer System

• A computer is an electric device capable of performing commands. The basic commands that a computer perform are input (get data), output (display result), storage, and arithmetic and logic operations.

• Hardware• CPU• Main memory• Secondary storage• Input/Output devices• Software


Hardware

- Major hardware components include:• CPU• Main memory: RAM (Random Access Memory)• Input/output devices• Secondary storage


Central Processing Unit and Main Memory

• Central processing unit– Brain of the computer– Most expensive piece of hardware– Carries out arithmetic and logical operations


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Central Processing Unit and Main Memory (cont'd.)


Central Processing Unit and Main Memory (cont'd.)

• Random access memory• Directly connected to the CPU • All programs must be loaded into main memory before

they can be executed• All data must be brought into main memory before it can

be manipulated • When computer power is turned off, everything in main

memory is lost• Main Memory is an ordered sequence of cells. Each cell

has a unique location in Main memory called address of the cell


Secondary Storage

• Secondary storage: device that stores information permanently

• Examples of secondary storage:– Hard disks – Flash drives– Floppy disks– Zip disks– CD-ROMs– Tapes


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Input/Output Devices

• Input devices feed data and programs into computers– Keyboard – Mouse – Secondary storage

• Output devices display results– Monitor– Printer– Secondary storage


Software

• Software: programs that do specific tasks

• System programs take control of the computer, such as an operating system

• Application programs perform a specific task– Word processors– Spreadsheets– Games


The Language of a Computer

• Computer use Digital signals: sequences of 0s and 1s• Machine language: language of a computer which is a

sequence of 0s and 1s• Binary digit (bit):

– The digit 0 or 1 • Binary code:

– A sequence of 0s and 1s • Byte:

– A sequence of eight bits


The Language of a Computer (cont’d.)


The Language of a Computer (cont'd.)

• Every letter, number, or special symbol on your keyboard is encoded as a sequence of bits, each having a unique representation (Code).

• ASCII (American Standard Code for Information Interchange) – 128 characters– A is encoded as 01000001– 3 is encoded as 00110011


The Language of a Computer (cont'd.)

• EBCDIC– Used by IBM– 256 characters

• Unicode – 65536 characters– Two bytes are needed to store a character


The Evolution of Programming Languages

• Early computers were programmed in machine language

• To calculate wages = rates * hours in machine language:

100100 010001 //Load

100110 010010 //Multiply

100010 010011 //Store

• Problem: Very difficult to Remember theMachine language codes for various operations


The Evolution of Programming Languages (cont'd.)

• Assembly language instructions are mnemonic

• Assembler: translates a program written in assembly language into machine language



• Using assembly language instructions, wages = rates * hours can be written as:

LOAD rate

MULThour

STORwages



• High-level languages closer to natural languages

• High-level languages include Basic, FORTRAN, COBOL, Pascal, C, C++, C#, and Java

• Compiler: translates a program written in a high-level language machine language

• The equation wages = rate * hours can be written in C++ as:

wages = rate * hours;C++ Programming: Program Design Including Data Structures, Fifth Edition 23

Processing a C++ Program#include <iostream>using namespace std;int main() { cout << "My first C++ program." << endl;

return 0;}

Sample Run:

My first C++ program.


Processing a C++ Program (cont'd.)

• To execute a C++ program:– Use an editor to create a source program in

C++– Preprocessor directives begin with # and are

processed by a the preprocessor– Use the compiler to:

• Check that the program obeys the rules• Translate into machine language (object program)



• To execute a C++ program (cont'd.):– Linker:

• Combines object program with other programs provided by the SDK to create executable code

– Loader: • Loads executable program into main memory

– The last step is to execute the program


Summary• Computer: electronic device that can perform

arithmetic and logical operations• Computer system has hardware and software• Central processing unit (CPU): brain• Primary storage (MM) is volatile; secondary

storage (e.g., disk) is permanent• Operating system monitors the overall activity of

the computer and provides services.• Various kinds of languages, such as machine

language, assembly, high-level


an overview of computers and programming languages_ch01

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