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Computer Hardware is used for four basic functions: input, output, processing, and storage.

An input device: is a component, such as a mouse or keyboard, which allows the user to enter in data.

An output device: is a component, such as a monitor or printer, which displays data.

The processing device: is used to process data.

storage device: is used to store data either temporarily or permanent.

Half a byte (four bits) is called a nibble

In some systems, the term octet is used for an eight-bit unit instead of byte.

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The mostly known/popular input devices are keyboard(s) and mouse/mice.

Keyboard; is an input device that allows the user to enter data into the computer.

Enter or Return – Moves the cursor down one line and to the left margin. Enter also process commands such as choosing an option in a dialog (message) boxes and submitting a form.

DEL or Delete – Deletes the character at cursor and/or characters to the right of the cursor and all highlighted (or selected) text.

Backspace – Deletes the character to the left of the cursor and all highlighted text.

Space Bar – Moves the cursor one space at a time to the right.

Processor, Memory, Adapter cards (sound card, modem card, Video card, Network card), Ports, Drive bays, Power Supply.

DRIVE BAYS-An area of reserved space in a personal computer where hard or floppy disk Drives (or tape drives) can be installed/sit. The number of drive bays in a computer determines the total number of internal mass storage devices it can handle.

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Shift Key – Use the shift keys to type capital letters and to type the upper character on any keys with two characters on them.

Caps Lock – Locks the keyboard so it types capital letters (a light goes on when caps lock is on).

Tab – Moves the cursor five spaces to the right (number of spaces are usually adjustable). Tab moves to the next field in a form or table (Shift-Tab for previous field).

ESC or Escape – Cancels a menu or dialog box.

Arrow Keys – Moves the cursor around document without changing text.

Function Keys or F keys – Access commands by themselves or in combination with the three command keys; CTRL, SHIFT, and ALT

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Command or Special Keys

Command keys normally do nothing on their own but work in combination with other keys.

Each piece of software uses the command keys differently though there is a move to standardize some functions.

The Control key or Ctrl is often used to access commands.

The Alternative key or Alt is often used to access menus.

The Shift key is used to type capital letters.

The command keys are all used to move through documents and edit text faster and easier.

All buses consist of two parts — an address bus and a data bus. The data bus transfers actual data whereas the address bus transfers information about the data and where it should go. The address bus is used to identify particular locations (addresses) in main memory.

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Keyboard Shortcuts for Windows

CTRL+ESC: Open Start menu

ALT + Tab: Switch between open programs

ALT+F4: Quit program

Shift + Delete: Delete item permanently

Windows Program Key Combinations

CTRL+C: Copy

CTRL+X: Cut

CTRL+V: Paste

CTRL+Z: Undo

CTRL+B: Bold

CTRL+U: Underline

CTRL+I: Italize

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General Keyboard-Only Commands

F1: Starts Windows Help

F5: Refreshing

F10: Activates menu bar options

Shift+F10: Opens a shortcut menu for the selected item (this is the same as right-clicking an object

CTRL+ESC: Opens the Start menu (use the arrow keys to select an item)

ALT + Tab: Switch to another running program (hold down the ALT key and then press the Tab key to view the task-switching window)

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Is a device that controls the movement of the cursor or pointer on a display screen.

Cursor: is a special symbol, usually a solid rectangle or a blinking underline character that signifies where the next character will be displayed on the screen.

There are typically two buttons on a mouse, and several clicking techniques that can be utilized to interact with the computer.

It can be difficult to know when, how, and where to click. Below is a list of clicking techniques to help clear the confusion.

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Click

Use the left mouse button to click one time.

This technique is mainly used to select objects and to navigate through menus.

Double-Click

Use the left mouse button to click two times quickly.

This technique is used to open objects (icons, programs, etc).

Right-Click

Use the right mouse button to click one time.

This technique is used to access short cut menus in Windows 95 and other software programs.

Click and Drag

Use the left mouse button to click and hold down.

Move the mouse cursor to a new location and release the left mouse button.

This technique is used to move or select objects.

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The mostly known/popular output devices are monitor(s), printer(s) and/ or Speakers.

Monitor: is an essential output device that displays the most information as to what is happening inside the computer.

They receive information from the CPU and they translate the information into a comprehensible picture and words.

They have the option to adjust the position of the picture on the screen, as well as the size.

Adjusting the color, tint, position, and size are common functions available on most models of monitors, though the location of these controls may vary from monitor to monitor.

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Produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper transparencies.

some printers are combined with scanners and/or fax machines in a single unit.

A printer which is combined with a scanner can essentially function as a photocopier.

Monitor Printer

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Are the output devices which are used to convert electrical energy into sound.

They consist essentially a thin flexible sheet called diaphragm that is made to vibrate by electrical signal from amplifier.

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The primary hardware which is responsible for processing is Central Processing Unit (CPU).

The Central Processing Unit/Processor

It is the brain of a computer.

It executes the stored program instructions that accept the input, process the data, and produce the output.

It gives all of the instructions to all of the other parts of the computer.

It is the most important and the most expensive part of the computer.

The best-known and most widely used CPU at the moment is the ‘Intel Pentium’ processor.

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It consist of two parts namely the Control Unit and the Arithmetic/Logic Unit.

The Control Unit: Directs and coordinates most of the operations in the computer.

For every instruction, the control unit repeats a set of four basic operations called the Machine cycle:

Fetching the instruction or data item from memory,

Decoding the instruction into commands the computer understands.

Executing the commands, and, if necessary;

Storing, or writing the result to memory.

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Arithmetic/logic unit (ALU): Performs the execution part of the machine cycle.

Specifically, the ALU carries out three operations

Arithmetic operations – performing calculations, which include addition, subtraction, multiplication, and division

Comparison operations – comparing data items to determine if the first item is greater than, equal to, or less than the other item

Logical operations – working with conditions and logical operators such as AND, OR, and NOT

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Storage devices can be either temporary (primary) or permanent (secondary).

Temporary (Primary) Storage Areas

Registers, are temporary storage areas for instruction or data.

It is associated with the CPU, not memory.

They are temporary storage areas that assist transfers and arithmetic/logical operations.

They can operate very rapidly to accept, hold and transfer instructions or data used in performing arithmetic or logical comparisons-all under the direction of the control unit of the CPU.

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Many machines assign special roles to certain types of registers, including-

An accumulator, which collects the results of computations.

A storage register, which temporary hold data taken from or about to be sent to memory.

An address register, which tells where a given instruction or piece of data is stored in memory.

Each storage location in memory is identified by address; just as each apartment in an apartment building is identified by address, etc

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Memory (RAM)

Memory is also referred to as primary storage, primary memory, main storage, internal storage, and main memory

All these terms are used interchangeably.

Memory (also called Random Access Memory or RAM) is part of computer that holds data and instruction for processing.

Although closely associated with the CPU, memory is technically separated from it.

However, specific items such as microwave ovens may combine the CPU and memory on a single chip.

Memory is used only temporary, i.e. it holds your program and data only as long as your program is in operation.

Data and instructions are kept in secondary storage, usually on disk, when not in use.

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Data and instructions from an input device are put into memory by the CU.

Data is then sent from memory to the registers, where an arithmetic operation or logical operation is performed by an ALU.

After being processed the information is returned to memory, where it is held until it is ready to be incorporated into other calculations or released to an output unit.

Memory/RAM

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A storage device is the computer hardware that writes and/or reads data to and from storage media.

Secondary storage devices have controllers that contain software to manage the device and temporarily hold data as it is transferred between primary and secondary storage.

They retain data even if there is no power

Primary or temporary storage is faster than permanent storage and is used to hold data and instructions.

Processing Disk drives such as Hard drives, floppy disks, Zip drives, and CD- ROMs are all examples of permanent storage.

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Disk drives provide a means for permanently storing data.

All computer data are stored in digital form, a series of 0’s and 1’s called bits.

Bit is a short for binary-digit. Is the smallest unit of data in a computer.

A bit has a single binary value, either 0 or 1.

Eight bits grouped together is called a byte.

For example;

1 Kilobyte (KB) = 1024 bytes

1 Megabyte (MB) = 1,000,000 bytes

1 Gigabyte (GB) = 1,000,000,000 bytes

The four most popular secondary storage devices are hard disks, floppy disks, Zip drives and CDs/DVDs.

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Hard disks are fixed inside a sealed unit (the hard disk drive) that is permanently mounted in the system unit.

A hard drive stores data magnetically and is a read/write storage medium.

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A floppy drive can read from and write to a floppy disk.

Floppy disks are only capable of storing 1.44 MB of data.

The advantage is that they are easily transportable between PC floppy disk drives.

This means that you can store data from one PC onto a floppy disk and easily transfer it to another.

ZIP drives

A ZIP drive is a device that reads from and writes to a Zip disk, which is a removable magnetic medium that can store up to 750 MB

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The bad news for floppy disks is that new PC’s are unlikely to have a floppy disk drive fitted.

USB (Universal Serial Bus) portable disk drives commonly known as flash disks are now the norm.

They hold much more data (up to 8GB or more) and are extremely compact and transportable; they fit on a key ring.

Memory card is also used to store data permanently, for example, you can store data from the phone and easily transferred it to the PC.

The card reader reads data from the memory card to the PC.

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This is computer memory on which data has been pre-recorded.

After data is written to a ROM chip, it cannot be removed,

It only can read.

ROM is referred to as being nonvolatile.

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CD-ROM (Compact Disk, Read Only Memory) disks are used primarily for the distribution and installation of commercial software.

The disk is loaded into the CD-ROM drive and the software installation process usually starts automatically.

The drive can also be used for playing audio and visual media; music, games and video.

A CD-ROM disk stores approximately 700 Megabytes of data.

CD-ROM drive

Hard disk Drive

Floppy drive

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Now days CD-R (CD-Recordable) and CD-RW (CD-ReWritable) disks are commonplace.

Newer PC systems will include a CD ‘burner’; a drive that can write to CD-R and CD-RW disks.

DVD-ROM (Digital Versatile Disk, Read Only Memory) disks are similar to CD-ROM but hold more information; over 5 Gigabytes.

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The system Unit: Is a case that contains electronic components of the computer used to process data.

The case that houses the processor, motherboard, internal hard- and floppy disks, power supply, and the expansion bus.

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Components of the inside of system unit

power supply

ports

drive bays

processor

memory

sound card

video card

Modem

network card

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It is the main circuit board in the system unit,

It contains adapter cards, processor chips, and memory chips.

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The motherboard is a Printed Circuit Board that all the main internal components are connected to.

The lines on a circuit board are called traces and are circuits, or paths, that enable data, instructions, and power to move from component to component on the board.

This system of pathways used for communication and the protocol and methods used for transmission are collectively referred to as the bus.

A protocol is a set of rules and standards that any two entities use for communication.

Other hardware (like sound, graphical cards) may be found directly connected or connected via an expansion slot.

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Communication: Almost all communication between the PC and its peripherals, other PCs, and you, the user, goes through the motherboard.

Upgradability: The capabilities of your motherboard dictate to what extent you will be able to upgrade your machine.

Control: The motherboard contains the chipset and BIOS program, which between them control most of the data flow within the computer.

Performance: The motherboard is a major determining factor in your system’s performance, for two main reasons:

Determines what types of processors, memory, system buses, and hard disk interface speed your system can have, and these components dictate directly your system’s performance.

The quality of the motherboard circuitry and chipset themselves have an impact on performance.

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Organization: In one way or another, everything is eventually connected to the motherboard.

The way that the motherboard is designed and laid out dictates how the entire computer is going to be organized.

Processor Support: The motherboard dictates directly your choice of processor for use in the system.

Peripheral Support: The motherboard determines, in large part, what types of peripherals you can use in your PC.

For example, the type of video card your system will use (ISA, VLB, PCI) is dependent on what system bases your motherboard uses.

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Is a device that enables the playing and recording of audio by converting analog sound to digital format and vice-versa.

Graphics card

Is a device that translates image data from the computer into a format that can be displayed on the computer monitor screen.

Video Card or Video Graphic Adapter (VGA)

This is a board that plugs into a PC to give it display capabilities.

This translates data from the CPU into a format that a monitor can display.

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The PC motherboard contains (usually four) expansion slots that allow extra hardware devices to be connected.

The hardware printed Circuit Board or card plugs into the expansion slot and is then connected to the CPU by the system bus.

The three most commonly used expansion slot types are

PCI (Peripheral component interconnect) expansion slot used for high-speed input/output devices.

AGP (accelerated graphics port) expansion slot used for a video card.

The AGP expansion slot connects AGP video cards to a motherboard.

Video expansion cards are also known as graphic expansion cards.

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ISA (Industry Standard Architecture) expansion slot used by older and/or slower devices.

PCI ISA

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AGP expansion slot

How an AGP slot looks like.

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Bus is a channel that allows devices inside computer to communicate with each other.

This is a collection of wires through which data is transmitted from one part of a computer to another.

It is an internal communication line that connects the components housed in the PC system unit; disks, CPU, memory, input/output ports, expansion slots, etc.

It enables the different parts of the system to share data.

System bus: Communication among processors, memory and input/output devices.

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Bus width determines number of bits transmitted at one time.

The bus size indicates the number of wires in the bus.

For example, a 32-bit bus has 32 wires or connectors that transmit 32 bits simultaneously.

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The fig below shows the system bus that connects processor and memory (RAM)

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The system BIOS is the lowest-level software in the computer; it acts as an interface between the hardware (especially the chipset and processor) and the operating system.

The BIOS provides access to the system hardware and enables the creation of the higher-level operating system (DOS, Windows etc.) that you use to run your applications.

The BIOS is also responsible for allowing you to control your computer’s hardware settings, for booting up the machine when you turn on the power or hit the reset button, and various other system functions.

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Bios chip

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Complementary Metal-Oxide Semiconductor.

Is a chip that can maintain configuration information as long as it has an electrical charge.

It is used on system boards to remember hardware configuration information such as the presence of a hard drive, floppy drive or CD-ROM drive.

CMOS battery

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A port is a socket, usually at the back of the PC, that connects devices such as the monitor, keyboard, mouse or printer.

These are several types of ports

Serial ports connect devices like a modem that require data to be passed to them in a serial format; in other words, one bit at a time.

Parallel ports pass data to the connected device, usually a printer, one byte at a time.

Universal Serial Bus (USB) ports have in recent times become the most popular type of external connection; they are easy to use and extremely versatile.

These days every external device manufactured will almost certainly be USB connectable

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A modem (Modulator – Demodulator) is a device that allows computer information to be transmitted across the telephone network.

It is used to connect to ISP( Internet Service Provider) and get internet.

It is also known as a both input and output device.

A Ribbon cable (for drive data): (Also known as multi-wire planar cable) is a cable with many conducting wires running parallel to each other on the same flat plane. As a result the cable is wide and flat.

Its name comes from its resemblance to a piece of ribbon.

They are used in a PC to connect hard disk, CD and floppy.

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Power supply; is a critical component in a PC, as it supplies electrical power to every component in the system.

The basic function of the power supply is to convert the type of electrical power available at the wall socket to that which is usable by the computer circuitry.

Standard PC power supplies have two connectors for the system board: one for the floppy drive and four connectors for devices like hard drives and CD-ROMs (although these numbers vary depending on the manufacturer).

Power supply

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The process of entering data into computer is called data entry.

This process of entering data to a computer is done by user, in which data will be processed in order to get information.

User will use input devices such as keyboard and mouse to enter data in system then the data will be processed to produce information.

The result which is output will be shown in a monitor or through printed document.

Below are the procedures and diagram used by computer to execute data

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First: Data is entered through input devices e.g. keyboard

Second: Control Unit (CU): After receiving instruction from the main memory to sent signal and commands, CU sent signal and commands to various part of the computer system to prepare and accept the data.

After the data is processed it is sent back to main memory which stores it temporarily before the next command is executed.

The data is then sending to secondary storage devices after secondary storage device had received command from the Control Unit.

For the information to be put into a hard copy i.e. paper, the information moves from the secondary storage device to the main memory which waits for signals and commands from Control Unit.

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After receiving signal from the Control Unit that the output devices are ready to receive data, the main memory releases the data to the output devices like printers.