Chapter 2

Inside Computer

Components (Parts) of Computer

1. Processor (CPU)2. Main Memory (Primary : RAM) 3. Hard Disk (Secondary memory and removable storage)4. Input/Output Devices (Mouse, Keyboard, Printer etc.)5. Connection Ports6. Power supply7. Motherboard8. Monitor9. Bios

Units to measure CPU speed

• CPU speed is measured in megahertz and gigahertz.• Mega means million and Giga means billion. • Hertz is a unit of measurement that measures the

processing speed. It means cycles per second. • CPU needs one or more cycles to perform an action.

More cycles per seconds means that the CPU can process more instructions per second.

• So, the higher the processing speed, the faster the CPU can process instructions.

Units to measure CPU speed (Continued…)

1 Byte 8 Bits1 Kilobyte (KB) = 210 bytes1 Megabytes (MB) = 210 Kilobytes

= 210 × 210 Bytes= 220 bytes

1 Gigabytes (GB) = 210 Megabytes= 210 × 210 Kilobytes= 210 × 210 × 210 Bytes= 230 bytes

1 Gibibyte (GiB) 1.074 GB

CPU

• The Central Processing Unit (CPU), also called a processor, is like the brain of the computer. It executes instructions in response to commands.

• Whenever we press a key, click the mouse, or start an application, we send instructions to the CPU. These are all executed by the CPU.

• A processor’s speed is measured in Megahertz (MHZ), or Gigahertz (GHZ). Higher the speed, faster is the execution of instructions.

• The CPU is generally a 2 inch ceramic square with a silicon chip located inside. The chip is usually about the size of a thumbnail.

RAM vs ROMRAM is Random Access Memory. ROM is Read Only Memory.

RAM is the memory available for the operating system, programs and processes to use when the computer is running.

ROM is the memory that comes with your computer that is pre-written to hold the instructions for booting-up the computer.

RAM requires a flow of electricity to retain data (e.g. the computer powered on).

ROM will retain data without the flow of electricity (e.g. when computer is powered off).

RAM is a type of volatile memory. Data in RAM is not permanently written. When you power off your computer the data stored in RAM is deleted.

ROM is a type of non- volatile memory. Data in ROM is permanently written and is not erased when you power off your computer.

There are different types of RAM, including DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory).

There are different types of ROM, including PROM (programmable read-only memory) that is manufactured as blank memory (e.g. a CD-ROM) and EPROM (erasable programmable read-only memory).

Hard Disk• The hard disk drive is the data center of the computer.• The hard disk drive is usually found inside a computer.• Operating system, the documents and content that a user

creates and saves, the software to operate the computer, and the applications like Word processor and Scratch, are stored on the hard disk until explicitly deleted.

• Whatever information we save on a computer, is written to the hard disk, which can be retrieved later. It is a permanent storage device.

• The computer loads the instructions from secondary memory (hard disk) into main memory (RAM) as and when required.

Removable Storage devices

• Devices that can be removed from the computer and can be carried wherever required are called as Removable Storage Devices.

• Examples : CD/DVD, hard disk, pen drive etc.

Backup and its Importance/Uses• Making a copy of a document or information that you

create on the computer, is called taking backup. • Backup of content (documents, paintings, reports, etc.)

that you create is important.• Backup can be taken on CD/DVD, pen drive, a removable

hard disk, or another computer to which you have access.• We can also mail a copy to ourselves if we have Internet

connectivity.• We also get books, games, educational lessons on

CD/DVDs. These devices can also be used for distribution and sharing of resources.

How does input get converted to output?• An input device converts data and instructions entered using the

device into a pattern of electrical signals. • A user inputs data and instructions (example: using a keyboard),

initiates a task (example: using a mouse), transfers images (example: using a web camera), using the input devices.

• These signals correspond to binary code that can be processed by a digital computer.

• An output device reverses the process, translating the binary code into a form intelligible to the user.

• The computer displays processed information (example: a print out of the information or audio, video) through the output devices.

• Some devices can handle both input and output. The network device (called network card) in a computer is both input and output device.

Processing• Input devices are used to send information to

the computer and output devices are used to receive information from the computer.

• CPU is neither an input nor an output device. It takes information from the input devices, processes it and sends the result to the output devices. This is called processing.

NIC (Network Interface Card)• In computer networking, a NIC provides the hardware interface

between a computer and a network. A NIC technically is network adapter hardware in the form factor of an add-in card such as a PCI (Peripheral Component Interconnect) or PCMCIA (Personal Computer Memory Card International Association)card.

• Some NIC cards work with wired connections while others are wireless. Most NICs support either wired Ethernet or Wifi wireless standards. Ethernet NICs plug into the system bus of the PC and include jacks for network cables, while WiFi NICs contain built-in transmitters / receivers (transceivers).

• In new computers, many NICs are now pre-installed by the manufacturer. All NICs feature a speed rating such as 11 Mbps, 54 Mbps or 100 Mbps that suggest the general performance of the unit.

Connection PortsSome common ports and their details are as follows:1. PS/2 Port: Used to connect the mouse and keyboard.2. Ethernet Port: Used to connect the network cable.3. Audio In/Audio Out: Connect various audio devices,

including speakers, microphones, headsets, etc.4. VGA Port: Monitor is connected to this port.5. USB Port: The Universal Serial Bus port is one of the most

useful ports. These USB ports let you attach a variety of devices such as mouse, printers, keyboards, web cameras, USB/flash drives, and digital cameras to the computer quickly. Most peripherals have a USB version.

6. Power cord sockets.7. Fan.

Personal System/2 (PS/2) Video Graphics Array

PS/2 WiresEthernet Port and Wire

USB (Universal Serial Bus)

Case Fan Power cord sockets.

Audio In/Audio Out