INTRODUCTION TO COMPUTING Course Instructor: Asma Sanam Larik

PART I What is Computer ? What is Computer ? What is Hardware ? What is Hardware ? What is Software ? What is Software ? What are the Input/ Output Devices ? What are the Input/ Output Devices ? Von Neumann Architecture Von Neumann Architecture CPU CPU Introduction to Memory Introduction to Memory

What is a Computer? A Computer is a device that receives, stores, and processes information A Computer is a device that receives, stores, and processes information Different types of computers have different characteristics Different types of computers have different characteristics supercomputers: powerful but expensive; used for complex computations (e.g., weather forecasting, engineering design and modeling) supercomputers: powerful but expensive; used for complex computations (e.g., weather forecasting, engineering design and modeling) desktop computers: less powerful but affordable; used for a variety of user applications (e.g., , Web browsing, document processing) desktop computers: less powerful but affordable; used for a variety of user applications (e.g., , Web browsing, document processing) laptop computers: similar functionality to desktops, but mobile laptop computers: similar functionality to desktops, but mobile palmtop computers: portable, but limited applications and screen size palmtop computers: portable, but limited applications and screen size

Desktop Specifications purchasing a computer can be confusing purchasing a computer can be confusing sales materials contain highly technical information and computer jargon sales materials contain highly technical information and computer jargon the following specs describe two computer systems for sale in January, 2007 the following specs describe two computer systems for sale in January, 2007 Desktop 1 is a low-end system, inexpensive but with limited features Desktop 1 is a low-end system, inexpensive but with limited features Desktop 2 is a high-end system, uses the latest technology so expensive Desktop 2 is a high-end system, uses the latest technology so expensive

Hardware vs. Software the term hardware refers to the physical components of a computer system the term hardware refers to the physical components of a computer system e.g., monitor, keyboard, mouse, hard drive e.g., monitor, keyboard, mouse, hard drive the term software refers to the programs that execute on the computer the term software refers to the programs that execute on the computer e.g., word processing program, Web browser e.g., word processing program, Web browser hardware components software components

Common Desktop Hardware

von Neumann Architecture Although specific components may vary, virtually all modern computers have the same underlying structure Although specific components may vary, virtually all modern computers have the same underlying structure known as the von Neumann architecture known as the von Neumann architecture named after computer pioneer, John von Neumann, who popularized the design in the early 1950's named after computer pioneer, John von Neumann, who popularized the design in the early 1950's The von Neumann architecture identifies 3 essential components The von Neumann architecture identifies 3 essential components 1. Input/Output Devices (I/O) allow the user to interact with the computer 2. Memory stores information to be processed as well as programs (instructions specifying the steps necessary to complete specific tasks) 3. Central Processing Unit (CPU) carries out the instructions to process information

Central Processing Unit (CPU) the CPU is the "brains" of the computer, responsible for controlling its inner workings the CPU is the "brains" of the computer, responsible for controlling its inner workings made of circuitry – electronic components wired together to control the flow of electrical signals made of circuitry – electronic components wired together to control the flow of electrical signals the circuitry is embedded in a small silicon chip, 1-2 inches square the circuitry is embedded in a small silicon chip, 1-2 inches square despite its small size, the CPU is the most complex part of a computer despite its small size, the CPU is the most complex part of a computer (CPU circuitry can have 100's of millions of individual components) commercial examples: Intel Core 2 Duo, AMD Athlon, Motorola PowerPC G4 commercial examples: Intel Core 2 Duo, AMD Athlon, Motorola PowerPC G4

CPU (cont.) the CPU works by repeatedly fetching a program instruction from memory and executing that instruction the CPU works by repeatedly fetching a program instruction from memory and executing that instruction individual instructions are very simple (e.g., add two numbers, or copy this data) individual instructions are very simple (e.g., add two numbers, or copy this data) complex behavior results from incredible speed complex behavior results from incredible speed a 2.53 GHz Celeron D processor can execute 2.53 billion instructions per second a 2.53 GHz Celeron D processor can execute 2.53 billion instructions per second a 2.93 GHz Core 2 Duo processor can execute 2.93 billion instructions per second a 2.93 GHz Core 2 Duo processor can execute 2.93 billion instructions per second

Memory memory is the part of the computer that stores data and programs memory is the part of the computer that stores data and programs modern computers are digital devices, meaning they store and process information as binary digits (bits) modern computers are digital devices, meaning they store and process information as binary digits (bits) bits are commonly represented as either 0 or 1 bits are commonly represented as either 0 or 1 bits are the building block of digital memory bits are the building block of digital memory by grouping bits together, large ranges of values can be represented

Memory (cont.) modern computers use a combination of memory types, each with its own performance and cost characteristics modern computers use a combination of memory types, each with its own performance and cost characteristics main memory (or primary memory) is fast and expensive main memory (or primary memory) is fast and expensive data is stored as electric signals in circuitry, used to store active data data is stored as electric signals in circuitry, used to store active data memory is volatile – data is lost when the computer is turned off memory is volatile – data is lost when the computer is turned off examples: Random Access Memory (RAM), cache examples: Random Access Memory (RAM), cache secondary memory is slower but cheaper secondary memory is slower but cheaper use different technologies (magnetic signals on hard disk, reflective spots on CD) use different technologies (magnetic signals on hard disk, reflective spots on CD) memory is permanent – useful for storing long-term data memory is permanent – useful for storing long-term data examples: hard disk, floppy disk, compact disk (CD), flash drive examples: hard disk, floppy disk, compact disk (CD), flash drive

Memory (cont.) higher-end computers tend to have higher-end computers tend to have more main memory to allow for quick access to more data and programs more main memory to allow for quick access to more data and programs more secondary memory to allow for storing more long-term data more secondary memory to allow for storing more long-term data

Input/Output (I/O) input devices allow the computer to receive data and instructions from external sources input devices allow the computer to receive data and instructions from external sources examples: keyboard, mouse, track pad, microphone, scanner examples: keyboard, mouse, track pad, microphone, scanner output devices allow the computer to display or broadcast its results output devices allow the computer to display or broadcast its results examples: monitor, speaker, printer examples: monitor, speaker, printer

Software recall: hardware refers to the physical components of computers recall: hardware refers to the physical components of computers software refers to the programs that execute on the hardware software refers to the programs that execute on the hardware a software program is a sequence of instructions for the computer (more specifically, for the CPU) to carry out in order to complete some task a software program is a sequence of instructions for the computer (more specifically, for the CPU) to carry out in order to complete some task e.g., word processing (Microsoft Word, Corel WordPerfect) e.g., word processing (Microsoft Word, Corel WordPerfect) e.g., image processing (Adobe Photoshop, Macromedia Flash) e.g., image processing (Adobe Photoshop, Macromedia Flash) e.g., Web browsing (Internet Explorer, Mozilla Firefox) e.g., Web browsing (Internet Explorer, Mozilla Firefox)

Questions ???

PART II What are bits and Bytes? What are bits and Bytes? Boolean Operations Boolean Operations Flip Flop Gates Flip Flop Gates Organization of Main Memory Organization of Main Memory Hexadecimal Notation Hexadecimal Notation Magnetic Disks and Tapes Magnetic Disks and Tapes Representation of Data, Sound, Text, Images Representation of Data, Sound, Text, Images

Bits and Bit Patterns Bit: Binary Digit (0 or 1) Bit: Binary Digit (0 or 1) Bit Patterns are used to represent information. Bit Patterns are used to represent information. Numbers Numbers Text characters Text characters Images Images Sound Sound And others And others

Boolean Operations Boolean Operation: An operation that manipulates one or more true/false values Boolean Operation: An operation that manipulates one or more true/false values Specific operations Specific operations AND AND OR OR XOR (exclusive or) XOR (exclusive or) NOT NOT

Figure 1.1 The Boolean operations AND, OR, and XOR (exclusive or)

Gates Gate: A device that computes a Boolean operation Gate: A device that computes a Boolean operation Often implemented as (small) electronic circuits Often implemented as (small) electronic circuits Provide the building blocks from which computers are constructed Provide the building blocks from which computers are constructed VLSI (Very Large Scale Integration) VLSI (Very Large Scale Integration)

Figure 1.2 A pictorial representation of AND, OR, XOR, and NOT gates as well as their input and output values

Flip-flops Flip-flop: A circuit built from gates that can store one bit. Flip-flop: A circuit built from gates that can store one bit. One input line is used to set its stored value to 1 One input line is used to set its stored value to 1 One input line is used to set its stored value to 0 One input line is used to set its stored value to 0 While both input lines are 0, the most recently stored value is preserved While both input lines are 0, the most recently stored value is preserved

Figure 1.3 A simple flip-flop circuit

Figure 1.4 Setting the output of a flip-flop to 1

Figure 1.4 Setting the output of a flip-flop to 1 (continued)

Figure 1.5 Another way of constructing a flip-flop

Hexadecimal Notation Hexadecimal notation: A shorthand notation for long bit patterns Hexadecimal notation: A shorthand notation for long bit patterns Divides a pattern into groups of four bits each Divides a pattern into groups of four bits each Represents each group by a single symbol Represents each group by a single symbol Example: becomes A3 Example: becomes A3

Figure 1.6 The hexadecimal coding system

Main Memory Cells Cell: A unit of main memory (typically 8 bits which is one byte) Cell: A unit of main memory (typically 8 bits which is one byte) Most significant bit: the bit at the left (high-order) end of the conceptual row of bits in a memory cell Most significant bit: the bit at the left (high-order) end of the conceptual row of bits in a memory cell Least significant bit: the bit at the right (low-order) end of the conceptual row of bits in a memory cell Least significant bit: the bit at the right (low-order) end of the conceptual row of bits in a memory cell

Figure 1.7 The organization of a byte-size memory cell

Main Memory Addresses Address: A “name” that uniquely identifies one cell in the computer’s main memory Address: A “name” that uniquely identifies one cell in the computer’s main memory The names are actually numbers. The names are actually numbers. These numbers are assigned consecutively starting at zero. These numbers are assigned consecutively starting at zero. Numbering the cells in this manner associates an order with the memory cells. Numbering the cells in this manner associates an order with the memory cells.

Figure 1.8 Memory cells arranged by address

Memory Terminology Random Access Memory (RAM): Memory in which individual cells can be easily accessed in any order Random Access Memory (RAM): Memory in which individual cells can be easily accessed in any order Dynamic Memory (DRAM): RAM composed of volatile memory Dynamic Memory (DRAM): RAM composed of volatile memory

Measuring Memory Capacity Kilobyte: 2 10 bytes = 1024 bytes Kilobyte: 2 10 bytes = 1024 bytes Example: 3 KB = 3 times1024 bytes Example: 3 KB = 3 times1024 bytes Sometimes “kibi” rather than “kilo” Sometimes “kibi” rather than “kilo” Megabyte: 2 20 bytes = 1,048,576 bytes Megabyte: 2 20 bytes = 1,048,576 bytes Example: 3 MB = 3 times 1,048,576 bytes Example: 3 MB = 3 times 1,048,576 bytes Sometimes “megi” rather than “mega” Sometimes “megi” rather than “mega” Gigabyte: 2 30 bytes = 1,073,741,824 bytes Gigabyte: 2 30 bytes = 1,073,741,824 bytes Example: 3 GB = 3 times 1,073,741,824 bytes Example: 3 GB = 3 times 1,073,741,824 bytes Sometimes “gigi” rather than “giga” Sometimes “gigi” rather than “giga”

Mass Storage On-line versus off-line On-line versus off-line Typically larger than main memory Typically larger than main memory Typically less volatile than main memory Typically less volatile than main memory Typically slower than main memory Typically slower than main memory

Mass Storage Systems Magnetic Systems Magnetic Systems Disk Disk Tape Tape Optical Systems Optical Systems CD CD DVD DVD Flash Drives Flash Drives

Figure 1.9 A magnetic disk storage system

Figure 1.10 Magnetic tape storage

Figure 1.11 CD storage

Files File: A unit of data stored in mass storage system File: A unit of data stored in mass storage system Fields and keyfields Fields and keyfields Physical record versus Logical record Physical record versus Logical record Buffer: A memory area used for the temporary storage of data (usually as a step in transferring the data) Buffer: A memory area used for the temporary storage of data (usually as a step in transferring the data)

Figure 1.12 Logical records versus physical records on a disk

Representing Text Each character (letter, punctuation, etc.) is assigned a unique bit pattern. Each character (letter, punctuation, etc.) is assigned a unique bit pattern. ASCII: Uses patterns of 7-bits to represent most symbols used in written English text ASCII: Uses patterns of 7-bits to represent most symbols used in written English text Unicode: Uses patterns of 16-bits to represent the major symbols used in languages world side Unicode: Uses patterns of 16-bits to represent the major symbols used in languages world side ISO standard: Uses patterns of 32-bits to represent most symbols used in languages world wide ISO standard: Uses patterns of 32-bits to represent most symbols used in languages world wide

Figure 1.13 The message “Hello.” in ASCII

Representing Numeric Values Binary notation: Uses bits to represent a number in base two Binary notation: Uses bits to represent a number in base two Limitations of computer representations of numeric values Limitations of computer representations of numeric values Overflow – occurs when a value is too big to be represented Overflow – occurs when a value is too big to be represented Truncation – occurs when a value cannot be represented accurately Truncation – occurs when a value cannot be represented accurately

Representing Images Bit map techniques Bit map techniques Pixel: short for “picture element” Pixel: short for “picture element” RGB RGB Luminance and chrominance Luminance and chrominance Vector techniques Vector techniques Scalable Scalable TrueType and PostScript TrueType and PostScript

Representing Sound Sampling techniques Sampling techniques Used for high quality recordings Used for high quality recordings Records actual audio Records actual audio MIDI MIDI Used in music synthesizers Used in music synthesizers Records “musical score” Records “musical score”

Figure 1.14 The sound wave represented by the sequence 0, 1.5, 2.0, 1.5, 2.0, 3.0, 4.0, 3.0, 0

Questions ???