Chapter 1.1

DESCRIBING COMPUTER ORGANIZATION – HARDWARE & SOFTWARE Chapter 1.1:

What is Programming?  Computer programming  the art and science of designing and writing computer programs.  Computer program  a sequences of instructions written in a programming language to achieve a task/to solve a problem.

What is a computer?  Hardware  The physical, tangible parts of a computer keyboard, monitor, disks, wires, chips, etc.  Software  Programs and data  A program is a series of instructions  A computer requires both hardware and software  Each is essentially useless without the other

Computer Organization Computer System Organization Hardware •CPU •Main Memory (RAM) •Secondary Storage •I/O Device Software •System Programs •Application Programs

Hardware Components of a Computer

Hardware Components of a Computer – motherboard processor chip adapter cards memory chips memory slots motherboard Expansion slots for adapter cards

Hardware Components of a Computer  CPU  Brain of the computer, most expensive, the faster computer.  CPU components– control unit, program counter, register instruction, arithmetic logic unit, accumulator.  RAM  Temporary memory, volatile, directly connected to the CPU, using memory cells unit.

Hardware Components of a Computer  SECONDARY STORAGE  Provides permanent storage for information.  Examples of secondary storage: ○ Hard disks ○ Floppy disks ○ Zip disks ○ CD-ROMs ○ Tapes.

RAM vs Secondary Storage  Primary memory  Volatile  Fast  Expensive  Low capacity  Works directly with the processor  Secondary Storage  Nonvolatile  Slow  Cheap  Large capacity  Not connected directly to the processor

Hardware Components of a Computer  INPUT DEVICES Sheet-fed

Hardware Components of a Computer  OUTPUT DEVICES

CPU and Main Memory Central Processing Unit Main Memory Chip that executes program commands Eg. Intel Pentium 4 Sun ultraSPARC III Primary storage area for programs and data that are in active use Synonymous with RAM

Secondary Memory Devices Central Processing Unit Main Memory Floppy Disk Hard Disk Secondary memory devices provide long-term storage Information is moved between main memory and secondary memory as needed Hard disks Floppy disks USB drives Writable CDs Writable DVDs Tapes

Input / Output Devices Central Processing Unit Main Memory Floppy Disk Hard Disk Monitor Keyboard I/O devices facilitate user interaction Monitor screen Keyboard Mouse Joystick Bar code scanner Touch screen

Software  In contrast to hardware, software is an abstract, intangible entity.  Software can be categorized as system or application software (refer next slide)  It consists of program and data to be used to perform certain tasks  A program is a sequence of simple steps and operations, stated in a precise language that the hardware can interpret  The process of programming involve algorithm design & coding.

Software Categories  System Software  Systems programs keep all the hardware and software running together smoothly  The most important system software is the operating system (OS)  controls all machine activities  provides the user interface to the computer  manages resources such as the CPU, memory & I/O  Windows XP, Unix, Linux, Mac OS  Application Software  generic term for any other kind of softwares  word processors, Spreadsheets, Web browsers, games

Algorithm  Algorithm refers to the strategy to solve a problem  It is a clear step by step sequence of instructions that describes how to accomplish a certain task.  2 ways can be used to represent algorithm: a) pseudocode ○ using english-like-phrases to describe the algorithm b) flowchart ○ using diagrams that employ the symbol to describe the algorithm.

Coding  Algorithm need to be translated into computer language so that it can be executed  Coding refers to the process of expressing algorithm in a programming language  The product of coding is a program.  The act of carrying out the instructions contained in a program is called program execution  A computer program is stored internally as a series of binary numbers known as the machine language of the computer

Digital Information  Computers store all information digitally:  numbers  text  graphics and images  video  audio  program instructions  In some way, all information is digitized - broken down into pieces and represented as numbers

Representing Text Digitally  For example, every character is stored as a number, including spaces, digits, and punctuation  Corresponding upper and lower case letters are separate characters H i , H e a t h e r . 72 105 44 32 72 101 97 116 104 101 114 46

American Standard Code for Computer InterChange (ASCII)  The ASCII data set  128 characters (0 until 127)  Character A in ASCII  01000001

Binary Numbers  Once information is digitized, it is represented and stored in memory using the binary number system  A single binary digit (0 or 1) is called a bit  A byte consists of 8 bits.  Each byte in main memory resides at a numbered location called its address.

Memory Main memory is divided into many memory locations (or cells) 9278 9279 9280 9281 9282 9283 9284 9285 9286 Each memory cell has a numeric address, which uniquely identifies it

Storing Information 9278 9279 9280 9281 9282 9283 9284 9285 9286 Large values are stored in consecutive memory locations 10011010 Each memory cell stores a set number of bits (usually 8 bits, or one byte)

Storage Capacity  Every memory device has a storage capacity, indicating the number of bytes it can hold  Capacities are expressed in various units: KB 210 = 1024 MB 2 20 (over 1 million) GB 2 30 (over 1 billion) TB 240 (over 1 trillion) Unit Symbol Number of Bytes kilobyte megabyte gigabyte terabyte

Chapter 1.1

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Chapter 1.1