1-1 ICS102: Introduction To Computing I King Fahd University of Petroleum & Minerals College of Computer Science & Engineering Information & Computer Science Department Web site: webcourses.kfupm.edu.sa

1-2 Today’s Class Course overview Introduction to Computer Systems  What is both Computer and Computer Science?  Components of a Computer System  Computer Hardware  Fetch-Decode-Execute Cycle  Computer Software

1-3 Text Book and Grading Criterion Textbooks: -“ABSOLUTE JAVA” by WALTER SAVITCH, Addison Wesley, 2 nd edition, ActivityWeight Lab20% Quizzes (4)10% Homework's (5)10% Major Exam 1 (Mar 28, 2007, 7:00 PM - 9:00 PM) 15% Major Exam 2 (May 9, 2007, 7:00 PM - 9:00 PM) 20% Final ( June 5, 2007, 7:00 PM - 9:00 PM )25% Grade Distribution:

1-4 Computer and Computer Science: Definition  A computer is an electronic device, which can input, process, and output data. inputprocessingoutput  A computer Science is the discipline that seeks to build a scientific foundation for such topics as computer design, computer programming, information processing, and algorithmic solutions of problems. A computer is a machine that stores data, interact with devices, and execute programs (provides computing capabilities to its users).

1-5 Major Components of a Computer System  A computer system consists of two main parts: hardware and software.  Hardware is the electronic and mechanical parts of a computer system.  Software is the data and the computer programs of a computer system.

1-6 Computer Hardware Basic hardware components Computer hardware is divided into three major Components: 1. The Central Processing Unit (CPU) 2. Computer memory 3. Input/Output (I/O) devices

1-7 CPU  The CPU is the "brain" of the computer system.  It does the fundamental computing within the system  It directly or indirectly controls all the other components  The CPU has a limited storage capacity. It relies on memory to hold data and programs and to save results.  The CPU consists of: 1. The Arithmetic and Logic Unit (ALU). 2. The Control Unit (CU). 3. Registers.  The CPU components are connected by a group of electrical wires called the CPU bus.

1-8 CPU PC: Program Counter Register MAR: Memory Address Register MDR: Memory Data Register  The CPU is connected to memory and I/O devices by the System bus  The System bus consists of: Address-, Control- and Data-buses.

1-9 Computer Memory  The main function of computer memory is to store software.  Computer memory is divided into primary memory and secondary memory.  Primary memory is divided into random access memory (RAM) and read-only memory (ROM):  RAM holds the programs and data that the processor is actively working with.  ROM contains software that is used in Input/Output operations. It also contains software that loads the Operating System in Primary Memory.  The CPU can read and write to RAM but it can only read from ROM.  RAM is volatile while ROM is not.  Secondary memory is used for long-term storage of programs and data.  Examples of secondary memory devices are: hard disks, floppy disks and CD ROMs.

1-10 Primary Memory  Primary memory is divided into a number of memory cells (bits) or bytes.  A bit (binary digit) is the smallest storage unit within a computer. It is a tiny electrical circuit that can be in one of two states:  A voltage high represented by the symbol 1  A voltage low represented by the symbol 0  Any system of symbols can be represented by bit or byte patterns.  Each byte has a unique integer address and it is usually 8 bits.

1-11 Primary Memory UNITSYMBOLPOWER OF 2 Number of bytes Byte KilobyteKB ,024 MegabyteMB ,048,576 GigabyteGB ,073,741,824 TerabyteTB ,099,511,627,776

1-12 Primary and Secondary Memory Comparison Primary memory Secondary memory Fast Expensive Low capacity Connects directly to the processor Slow Cheap Large capacity Not connected directly to the processor

1-13 I/O (Input/Output)Devices  Input devices are used to enter programs and data into a computer.  Examples: keyboard, mouse, microphone, scanner, and bar code reader.  Output devices are where program output is shown or is sent.  Examples: monitor, printer, and speaker.  An I/O device is directly connected to the System, but through a device controller.

1-14 Fetch Decode Execute Cycle  The CPU continuously transfers data to and from the primary memory  Data transfer is done in units called instructions or words  When a computer is switched on, the CPU continuously goes through a process called fetch-decode-execute cycle:  The Control Unit fetches the current instruction from memory, decodes it and instructs the ALU (Arithmetic Logic Unit) to execute the instruction.  The execution of an instruction may generate further data fetches from memory  The result of executing an instruction is stored in either a register or RAM

1-15 Fetch-Decode-Execute Cycle (cont’d) Main Memory Control Unit Arithmetic/Logic Unit Instruction Cycle Execution Cycle FetchDecode Execute Store cpu RAM

1-16 Computing Environments Personal computing Time-sharing Distributed computing

1-17 Software  Software is the programs and data that a computer uses.  Programs are lists of instructions for the processor  Data can be any information that a program needs: character data, numerical data, image data, audio data, etc.  Both programs and data are saved in computer memory in the same way.  Computer software is divided into two main categories: 1. Systems software 2. Applications software  System software manages computer resources and makes computers easy to use.  An applications software enables a computer to be used to do a particular task.

1-18 Computer Software Types of software Software

1-19 Software Application ProgramsSystems Programs   Word processors  Game programs Spreadsheets Data base systems Graphics programs Web browsers   Operating system. Networking system. Programming language software. Web site server. Data backup.

1-20 Operating Systems  The most important systems program is the operating system.  It is a group of programs that coordinates the operation of all the hardware and software components of the computer system.  It is responsible for starting application programs running and finding the resources that they need.  Examples of operating systems are: Unix, Windows NT, Windows XP, MS-DOS, Linux, Solaris, VMS, OS/2 and System 7.

1-21 Computer Languages Computer language evolution The only language understood by a computer is machine language. Note:

1-22 Writing, Editing, Compiling, and Linking Programs Primary Memory Disk Editor Compiler Class Loader Program is created in an editor and stored on disk in a file ending with.java. Compiler creates bytecodes and stores them on disk in a file ending with.class. Class loader reads.class files containing bytecodes from disk and puts those bytecodes in memory. Phase 1 Phase 2 Phase 3 Primary Memory Bytecode Verifier Bytecode verifier confirms that all bytecodes are valid and do not violate Java’s security restrictions. Phase 4 Primary Memory Interpreter Interpreter reads bytecodes and translates them into a language that the computer can understand, possibly storing data values as the program executes. Phase 5 typical Java environment

1-23 Program Execution Executing programs

1-24 System Development Model Figure 1-12 System development model An old programming proverb: Resist the temptation to code. Note: Pseudocode A precise algorithmic description of program logic. Note: