1. An overview of Computer System
Unit-1
An overview of Computer System

2. 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.
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3. Block Diagram of Digital Computer
Random-access memory
(RAM)
Central processing unit
(CPU)
Input-output processor
(IOP)
Input
devices
Output
Block diagram of a digital computer

4. 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… )

5. Generations of Computers
First generation: Vacuum tube computers (1940s 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.

6. Generations of Computers
Second generation (1950s): 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

7. Generations of Computers
Third generation (1960s and 1970s): 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

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

9. 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

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

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

12. 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.

13. 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”

14. 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

15. Access Speed Increases Storage Capacity Decreases
Primary & Secondary Storage Media
Semiconductor
Memory
Magnetic
Disks
Floppy Disk
Hard Disk, RAID
Magnetic Tape
Optical Disks
CD-ROM, CD-R
CD-RW
DVD
Access Speed Increases
Storage Capacity Decreases
Cost per Bit Increases
Direct
Access
Sequential
Secondary Storage
Primary
Storage

16. 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

17. 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"

18. 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

19. 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 = 1,000,000 (MB) Million
Giga = 1,000,000,000 (GB) Billion
Bytes are composed using either the ASCII coding system (7 bits = character) or EBCDIC (8 bits = character)

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

21. Output Devices
Output Devices are used to take output from computer system. These are as follows
Monitor
Printer
Plotter