Unit1 An overview of Computer System Anatomy of

Unit-1 An overview of Computer System

Anatomy of a digital Computer Definition of Computer • A device that accepts data, processes the data in accordance with a stored program, generates results, and usually consists of input, output, storage, arithmetic, logic, and control units. • A machine for manipulating data according to a list of instructions known as a program. …cntd

Block Diagram of Digital Computer Random-access memory (RAM) Central processing unit (CPU) Input devices Input-output processor (IOP) Output devices Block diagram of a digital computer

Block Diagram of Digital Computer • A digital computer consists of a number of processors interconnected with memory and Input/Output devices • A Processor or CPU (Central Processing Unit) fetches instructions from memory, and executes them one after another • A Memory is where programs and data are stored • I/O devices allow for interaction between users and computer (printers, keyboard, mice… )

Generations of Computers • First generation: Vacuum tube computers (1940 s - 1950 s) • First Generation Electronic Computers used Vacuum Tubes • Vacuum tubes are glass tubes with circuits inside. • Vacuum tubes have no air inside of them, which protects the circuitry.

Generations of Computers • • • Second generation (1950 s): Transistors Uses Silicon developed in 1948 won a Nobel prize on-off switch Second Generation Computers used Transistors, starting in 1956 • Replaced vacuum tubes with Transistors

Generations of Computers • Third generation (1960 s and 1970 s): Integrated circuits • Third Generation Computers used Integrated Circuits (chips). • Integrated Circuits are transistors, resistors, and capacitors integrated together into a single “chip” • Operating System • Software – Instructions for Computer • Operating system is set of instructions loaded each time a computer is started • Program is instructions loaded when needed

Generations of Computers • Fourth generation (late 1970 s through present): LSI and VLSI – Personal computers, computer networks, WWW, etc. • The First Microprocessor – 1971 -Intel 4004 Microprocessor • The 4004 had 2, 250 transistors • 108 Khz • Called “Microchip”

Generations of Computers • Very Large Scale Integrated Circuit (VLSIC) – Transistors, resistors, and capacitors • 4004 had 2, 250 transistors where • Pentium IV has 42 MILLION transistors

Generations of Computers • Fifth generation- 21 st Century Computing • Great increases in speed, storage, and memory • Increased networking, speed in Internet • PDAs • Cell Phone/PDA • WIRELESS!!!

Major Hardware Components of a Computer System • • • CPU Main Memory Secondary Memory Input Devices Output Devices

Central Processing Unit • Control Unit: works with the operating system to move data between auxiliary storage and main memory; and between main memory and the ALU • Arithmetic/Logic Unit (ALU): processes data arithmetically (addition, subtraction, multiplication, division) or logically (greater than, less than, equal to) • Main Memory: contains both program instructions and the data that is required. • A single machine can have multiple CPUs to share processing tasks (co-processors, multiprocessing), but each CPU can execute only a single task.

Inside the System Unit • Main component: motherboard – Circuit board that “houses” integrated circuits (microscopic elements … wires, transistors, etc…) required to make the digital pulse flow inside of the computer. Pulses flow from component to component via the “bus”

Motherboard (cont. ) – Attachments to the motherboard include: • Main Memory: types of main memory include: – RAM - temporary (includes virtual memory storage). Include RAM cache – ROM - permanent – When add main memory, make sure add-on chips are compatible • Real time clock (current date and time) • Microprocessor or CPU (central processing unit) – Control Unit: traffic cop portion of the CPU – ALU: arithmetic logic unit processes all math and logical operations performed by the computer

Magnetic Tape Optical Disks CD-ROM, CD-RW DVD Primary Storage Semiconductor Memory Magnetic Disks Floppy Disk Hard Disk, RAID Direct Access Sequential Access Direct Access Secondary Storage St Acc or es ag s Co e C Spe ap ed st ac In pe r B ity cr De ea it s In cr crea es ea se ses s Primary & Secondary Storage Media

Memory Units- a unit for measuring computer memory • Unit - any division of quantity accepted as a standard of measurement or exchange; "the dollar is the United States unit of currency"; "change per unit volume" • Nibble - a small byte • Byte - a sequence of 8 bits (enough to represent one character of alphanumeric data) processed as a single unit of information

Memory Units . . cntd • Sector - the minimum track length that can be assigned to store information; unless otherwise specified a sector of data consists of 512 bytes • Block - a sector or group of sectors that function as the smallest data unit permitted; "since blocks are often defined as a single sector, the terms `block' and `sector' are sometimes used interchangeably"

Main Memory • Stores Instructions and Data – Stored Program Concept • Random Access Memory (RAM): allows data and instructions to be accessed randomly from any memory location (address). Primary storage. – Volatile - lost when power is turned off • Read Only Memory (ROM): usually contains programs that help the computer system operate: – can only be read: cannot be written to or altered by the user (usually) – ROM is not volatile

Main Memory • Data and instructions are stored as BITS (binary digits). Everything from our world is translated into a computer recognizable format called binary (zeros or ones) – The combination of binary digits represents our letters or numbers. One character represented is equal to a byte. • Memory capacity is measured in bytes. Today’s most common measurement is megabytes Kilo = 1, 000 (KB) Thousand Mega = 1, 000 (MB) Million Giga = 1, 000, 000 (GB) Billion • Bytes are composed using either the ASCII coding system (7 bits = character) or EBCDIC (8 bits = character)

Input Devices • Input Devices are used to input the data to computer system. These are as follows ü Keyboard ü Mouse ü Trackball ü Touch Screen ü Optical Character Recognition ü MICR ü Scanners etc.

Output Devices • Output Devices are used to take output from computer system. These are as follows üMonitor üPrinter üPlotter