Calculators are used to increase speed and accuracy

Calculators are used to increase speed and accuracy of numerical computations The abacus has roots dating back over 5, 000 years Mechanical calculators have been relatively commonplace since late 19 th century What is a computer? A mechanical or electronic device Stores, retrieves, manipulates large amounts of data (information) at high speed, with great accuracy Does not need human intervention Carries out instructions from a program

Early Computers – 1945 – 1950’s: First generation computers • used vacuum tubes to do internal switching needed for computations • 1955: about 300 computers in the world built mostly by IBM and Remington Rand, based on vacuum tubes. – Late 1950 s: invention of the transistor was one of most important inventions of 20 th Century • computers based on the transistor are the first solid-state computers. – Early 1960’s: DEC created the minicomputer (Servers) – about the size of a file cabinet. • Used small packages of transistors called integrated circuits – Mainframes, such as the IBM 360 are prominent in large companies and Universities.

The Personal Computer – 1970 s: The personal computer becomes available with invention of the microchip – 1974: The microchip, along with the invention of the microprocessor led to creation of first personal computer – Bill Gates and Paul Allen founded Microsoft Corporation – Stephen Wozniak and Steven Jobs founded Apple Computer, Inc.

Computers Today • Currently: – PCs: 95% use Microsoft Windows operating system with a huge array of available software – Minicomputers (servers) are still popular with small business and universities. – Mainframes are in use at large corporations. – Supercomputers are very powerful and specialized • Used for massive computing problems by big corporations and government departments.

Components and Operations • Hardware: equipment, or devices • Software: programs that contain instructions which tell the computer what to do – created by programmers • Hardware and software: the two major • components of any computer system • Major operations in a computer: – Input – Processing – Output

• Input devices: allow data to enter the computer – Mouse, keyboard, scanner • Output devices: allow processed data to be exported out of the computer – Printer, monitor, speakers • Processing: working on the data; such as: – Organizing data – Checking data for accuracy – Mathematical or other manipulations on data • Central Processing Unit (CPU): hardware that performs the tasks

• Components of a computer – Central Processing Unit (CPU) – Internal memory • RAM (Random Access Memory) • ROM (Read Only Memory) – Mass storage devices • Magnetic, optical, and solid-state – Input devices such as keyboard and mouse – Output devices such as monitor and printer

Central Processing Unit (CPU) • Often called the brain of the computer – Carries out program instructions ( in memory) – Performs arithmetic and logical operations Arithmetic Logical Unit (ALU) – Controls other computer components (operating system) • Consists of millions of transistors on a single microchip that plug into the motherboard

Internal Memory • ROM: read-only memory – Contains instructions used by computer during startup – Cannot be altered by computer user • RAM: random-access memory – Is a “scratch pad” for user as he or she works – Can be read from and written to – Operating System/Applications reside

• Storage categories: internal and external • Internal storage: – Main memory, random access memory (RAM) – Located inside the computer system – Volatile: contents are lost when power goes down • External storage: – Persistent: contents are relatively permanent – Floppy drive, hard drive, flash media, magnetic tape – Located outside the computer system

Mass Storage Devices • Magnetic storage – Hard disks, floppy disks, zip drives – Hard disks are internal, others are external • Optical storage – CDs and DVDs • Solid-state storage – Flash drives plug into a USB port

Software • System Software – Control system resources – Operating systems – Windows, DOS, Linux, UNIX, dll, utilities, drivers • Application Software – – – Interract with a user Word Processors (MS Word) Database Managers (Access) Spreadsheets (Excel) Photo Editors Web browsers, email programs (Netscape)