Introduction to Computers … We will learn : Components of Computer: Hardware vs Software.

1. Introduction to Computers… • We will learn : • Components of Computer: Hardware • vs Software. • Components of Hardware: CPU, • Memory, Storage, Input/Output • Devices. • Components of Software: Operating • System and Application Programs. • STORAGE structure.

2. The Big Picture • A computer system contains: • hardware • (equipment) • software • (programs) • people • (programmers and • end-users)

3. Hardware: The Physical Components of a Computer Secondary storage device stores data and programs Secondary storage Central processing unit (CPU) executes computer instructions memory holds data and programs temporarily Input device Sends data to the central processing unit Output device makes processed data (information) available Input Processing Output

4. A computer is a machine that can • be programmed to • accept data • process it into useful information • store it away for safekeeping and later • use

5. Processing Unit • Processing Unit is composed of • Central Processing • Unit (CPU) that • executes program. • Main Memory that • stores program and • data.

7. Main Memory: Structure • Ordered sequence of • storage locations called • memory cells. • Each memory cell is • identified by a unique • address. • The data stored in a • memory cell is its • content. • One can either read a • memory cell or write to a • memory cell.

8. Main Memory: Data Representation in Memory Cells • Data represented as binary numbers (i.e. base 2) • which are collections of 1s and 0s. • Here 1 and 0 correspond to two different levels • of voltage in electrical implementation of the • memory. For example: 0 0 Volts • 1 5 Volts. • 1or 0 is a binary digit, which is abbreviated as bit. • Each memory cell can hold a binary number • with 8 bits which is called a byte.

9. Main Memory: Operations READ Address CPU MEMORY Data WRITE Address CPU MEMORY Data

10. Main Memory: Memory Sizes 1 byte = 8 bits. 1 kilobyte = 210 or 1024 bytes. 1 Megabyte = 220 or 1,0548,786 bytes. 1 Gigabyte = 230 or 1,073,741,824 bytes. Typical PC Main Memory is 256 Megabyte to 4 Gigabyte. (as of year 2004)

11. Storage • Primary storage (or memory) holds • programs and data temporarily: Main Memory. • Secondary storage devices such as disks • store data and programs.

12. Secondary Storage • Secondary storage has more size than Main • Memory (i.e. Primary Memory). • It is non-volatile, when you power down the • computer data is not lost. • We use secondary storage to store our • programs and data that we want to save.

13. Software: • Telling the Machine What to Do • Software - the planned, step-by-step set of • instructions required to turn data into information. • Divided principally into systems and applications.

14. Hardware & Software: Structure • Hardware • Operating System • Application Programs • User

15. Software: Operating System • Controls the interaction of the computer with its • environment (including user). • Management of memory, processor time and • other resources for various tasks. • Execute and provide services for applications. • Examples: Windows 2000, Unix, Linux,…

16. Software: Applications Software • Programs designed to • perform specific tasks • and functions. • Examples: Matlab, • Excel, Microsoft Word, • and many more…. • Often found in the mass • market as • packaged software or • commercial software

17. Software: Organization • (Files, Folders, Drives, Path) • Your computer’s filing system has three basic • divisions: files, folders and drives • Everything saved on your computer is stored as a file • You can store a file in a folder (called “directory” under UNIX), and in turn store that folder inside another folder. Your computer also stores files in folders. When computer needs one of those files, it follows a path to the folder, and then to the file. • Files and folders are stored on drives. Each drive is assigned a letter name. Hard drive (C:\), floppy drive (A:\), CD-ROM drive, network drive, etc.

18. Software Organization Disk Drive Files Folders Files Folders Files Folders

19. Software:Organization Examples • Disk Drives under My Computer (Windows)

20. Software: Organization Examples • Example CD-ROM Drive Contents: Files and • Folders

21. Software : Organization Examples • Example Folder (A folder of the CD-ROM in the • previous slide.)

23. Programming Languages • A programming language is a set of rules that • provides a way of telling a computer what • operations to perform. • There are several levels (or “generations”) of • programming languages: • High-level • Assembly • Machine

24. High-Level Language • High-level languages use English-like words • that are much easier for humans to understand. • A translator is needed to convert the high-level • language into machine language that computers • understand. • There are several languages that you can use • to write programs: • • FORTRAN • COBOL • RPG • • BASIC • Pascal • VB • • C • C++• C# • • Perl • Java • ..?...

25. Assembly Language • Assembly languages are written using • mnemonic codes and assemblers replace • mnemonic codes with 0s and 1s to create • machine code. • Since machine language is the only language • the computer can execute, assembly language • is eventually translated into machine language • to execute the program.

26. Machine Language • This is the lowest level of programming • language because it represents data and • program instructions as 0s and 1s. • All programs written in different programming • languages are eventually converted into • machine language.

27. Example for a = a + b

28. Compiler, linker, loader… Compiler Source File (Text) Object File (binary) Library Linker Other Object Files (binary) Executable File (binary) Loader Input Results