What is a computer ?
• A Computer is an electronic device which takes input through input
devices, processes it and gives the output through output devices.
• It also stores data for further processing.
• Computer works with 0’s & 1’s(Binary).
• Like all electronic devices a computer works with DC power supply.
Block diagram of a computer
RAM(Random Access Memory)
• Primary storage for the CPU.
• Integrated circuits (chips) are used to temporarily store programs,
instructions and data.
• It is a volatile memory (requires power to store the data).
Static Ram (Cache Memory)
• The CPU process data at a very high speed.
• Dynamic RAM cannot match that speed.
• Hence, a special type of RAM called as cache is used.
• Cache memory stores instructions and data which the CPU is
currently working on or may soon need.
• Cache levels:
– The cache memory that is placed inside the actual CPU is called level l cache
(internal cache memory).
– The cache memory located on the die of the CPU is called as level ll cache
(external cache memory).
ROM(Read Only Memory)
– Integrated circuits that are used to permanently store start-up (boot)
instructions and other critical information.
• Types of ROM:
-PROM(Programmable Read Only Memory)
-EPROM(Erasable Programmable Read Only Memory)
-EEPROM (Electrically Erasable Programmable Read Only Memory)
BIOS (Basic input output system)
• During the boot up it performs POST(Power On Self Test)
• Recognizes the hardware devices
• Locates and loads the operating system
• It helps the operating system to access the hardware devices
Components on the motherboard
• Processor slot/socket
• Memory Slots
• Expansion Slots
• I/O Ports
• IDE / SATA Connectors
• Floppy Drive Connector
• CMOS Battery
• Power Supply connector
• Heat Sink
• Front Panel Connectors
Input / Output (I/O) PORTS
Back panel connectors:
• PS/2(Personal System v2):
Used to connect keyboard and mouse
• USB(Universal Serial Bus):
Used to connect various USB enabled devices
(Webcam,Pendrive,External Hard disk ,Modems,etc)
• VGA (Visual Graphic Adapter)(15-pin female):
Used to connect display devices like LCD,monitor,projector etc
Back panel connectors:
• Serial port(9-pin male):
Used to connect PC to modems
Also called as Com port
• LAN Port :
Used to connect PC to the Local Area Networks.
• NORTH BRIDGE:
– It controls the processor
and RAM (high speed devices)
– It is placed nearer to the processor
– It also contains graphic processor
– It is also called as GMCH
(Graphic Memory Controller Hub)
• SOUTH BRIDGE :
– It controls low speed devices like I/O ports, slots etc
– It is placed nearer to the slots
– It is also called as IOCH
(Input Output Controller Hub)
IDE and SATA Connectors
IDE and SATA connectors are used to connect Hard Disk, CD-ROM,
IDE(Integrated Drive Electronics)/Enhanced IDE
• IDE/EIDE cables are used to connect the devices to
SATA(Serial Advanced Technology Attachment)
• SATA cables are used to connect the devices to
the SATA ports
• CMOS(Complementary Metal Oxide Semiconductor) RAM is used to
store the date, time, and system configuration
• Battery which powers this memory is called as CMOS Battery
Secondary Storage Devices
• Magnetic storage devices
- Floppy disk
- Tape drive
- Zip drive
• Optical storage devices
– Compact Disc(CD)
– Digital Versatile Disc(DVD)
– Blu Ray Disc(BRD)
• Uses magnetic media for storing data
• Non-volatile permanent storage device
• Mass storage devices
• Interfaces used
– IDE / EIDE (Enhanced IDE)
• In CD or DVD data is stored in the form of lands and pits
• Land can reflect laser beam and pit will absorb the laser beam
• While reading data if the light emitted by laser is reflected then it is
treated as binary ‘1’ and if laser beam is not reflected then it is
treated as binary ‘0’