Java notes: Computers, software and different hardware components

A1) The term programming means to create (or develop software), which is also called a program.

A2) In basic terms, software contains instructions that tell a computer- or a computerized device what to do. We find and use software on personal computers, airplanes, cars, cell phones, and even toasters. On a personal computer, one uses word processors to write documents. web browsers to explore the internet, and email programs to send and receive emails. Software is the invisible set of instructions that control the hardware and make it perform specific tasks.

A3) Software developers create software with the help of powerful tools called programming languages.

A4) A computer is an electronic device that stores and processes data. A computer includes both hardware and software.

A5) There are six major hardware components in a computer:

1. A central processing unit (CPU)
2. Memory (main memory)
3. Storage devices (such as disks and CDs)
4. Input devices (such as mouse and keyboard)
5. Output devices (such as monitors and printers)
6. Communications devices (such as modems and network interface cards (NIC))

A6) A computer’s hardware components are interconnected by a subsystem called bus (something like a system of roads running between the hardware components). Data and power travel along the bus from one part of the computer to another. In personal computers, the bus is built into the computer’s motherboard.

A7) The motherboard is a circuit case that connects all the parts of a computer together.

A8) The central processing unit (CPU) is the brain of the computer. It retrieves instructions from the computer and executes them. The CPU has two components: a control unit and an arithmetic/ logic unit.

The control unit controls and coordinates the actions of other components.

The arithmetic/logic unit performs numeric operations (Addition, subtraction, multiplication, and division) and logical operations (comparisons).

Today’s CPUs are built on small silicon semiconductor chips that contain millions of tiny electronic switches, called transistors, for processing information.

A9) Every computer has an internal clock that emits electronic pulses at a constant rate. These pulses are used to control and synchronize the pace of operations. A clock speed enables the computer to execute more instructions in a given period of time.

The unit of measurement of clock speed is hertz (Hz), with 1hz equating to 1 pulse per second.

A10) The core is the part of the processor that performs the reading and executing of instructions. In order to increase the CPU’s processing power, chip manufacturer’s produce CPUs with multiple cores. A multicore CPU is a single components with two or more independent cores.

A11) A computer is nothing more than a series of switches. Each switch exists in two states: on or off. Storing information in a computer is simply a matter of setting a sequence of switches on or off. If the switch is on, the value is 1. If the switch is off the value is 0. These 0s and 1s are interpreted as the binary number system and are bits (binary digits).

A12) The minimum storage unit in a computer system is a byte. A byte is composed to 8 bits. A small number such as 3 can be stored as a single byte, To store a number that cannot be contained in a single byte, the computer uses several bytes.

A13) Data of various kinds, such as number and characters, are encoded as a series of bytes. An encoding scheme is a set of rules that govern how a computer translates characters and numbers into data with which the computer can actually work. Most schemes translate each character into a predetermined string of bits. In the popular ASCII encoding scheme, the character c is represented as 01000011 in 1 byte.

A14) A computer’s storage capacity is measured in bytes.

1. A Kilobyte (KB) is about 1000 (1024 to be exact) bytes.
2. A Megabyte (MB) is about 1 million bytes
3. A Gigabyte (GB) is about 1 billion bytes
4. A Terabyte (TB) is about 1 trillion bytes.

A computer’s memory consists of an ordered sequence of bytes for storing programs as well as data with which the program is working You can think of the memory as the computer’s work area for executing a program. A program and its data must be moved into the computer’s memory before they can be executed by the CPU.

The memory stores data and instructions in uniquely addressed memory locations.

A memory byte is never empty, but its initial content may be meaningless to your program.

Like the CPU, memory is built on silicon semiconductor chips that have millions of transistors embedded on it’s surface. Compared to CPU chips, memory chips are less complicated, slower, and less expensive.

A16) Every byte in the memory as a unique address. The address is used to locate the byte for storing and retrieving the data. Since the byes in the memory can be accessed in any random order, the memory is called random-access-memory (RAM).

Today’s computer;s have at least 4GB RAM.

Generally speaking, the more RAM a computer has, the faster it can operate.

A computer’s memory (RAM) is a volatile form of data storage. Any information that has been saved in memory is lost when system’s power is cut off.

A17) Programs and data are permanently stored on storage devices and are moved, when the computer actually uses them, to memory, which operates at much faster speeds that storage devices can. There are three main types of storage devices:

1. Magnetic disk drives
2. Optical disk drives (CD and DVD)
3. Universal Serial Bus (USB) flash drives

A18) Drives are devices for operating a medium, such as disk and CDs. A storage medium physically stores data and program instructions. The drive reads data from the medium and writes data onto the medium.

A19) A computer usually has at least one hard disk drive. Hard disks are used for permanently storing data and programs. Hard disks are usually encased inside the computer, but removable hard disks are also available.

A20) CD stands for Compact Disc. A single CD can hold upto 700MB. There are three types of CDs:

1. CD-ROM
2. CD-R
3. CD-RW

A CD-ROM is a prepressed disc. It is popular for distributing software, music, and video.
A CD-R (CD-Recordable) is write once medium. It can be used to record data once and read many number of times.
A CD-RW (CD-ReWritable) can be used like a hard disk; that is, you can write data onto the disc, then overwrite the data with new data.

A21) DVD stands for Digital Versatile Disc or Digital Video Disc. DVDs and CDs look alike and you can use either to store data. A DVD can hold more data than a CD; a standard DVD’s storage capacity is 4.7GB There are two types of DVDs:

1. DVD-R (DVD- Recordable)
2. DVD-RW(DVD-ReWritable)

A22) Universal Serial Bus (USB) connectors allow the user to attach many kinds of peripheral devices to the computer. You can use a USB to connect to a printer, digital camera, mouse, external hard disc drive, and other devices to the computer.

A USB Flash Drive is a device used for storing and transporting data. A flash drive is small- about the size of a pack of gum. It acts like a portable that can be plugged into your computer’s USB port. USB’s storage capacity extends up to 256 GB.

A23) Input and Output devices help the user communicate with the computer.

A24) A keyboard is a type of input device used for entering input. Compact keyboards are available without a numeric keypad.

Functions keys are located across the top of the keyboard and are prefaced with the letter F. Their functions depend on the software currently being used.

A modifier key is a special key (such as shift, alt, and ctrl keys) that modifies the normal action of another key when the two keys are pressed simultaneously.

The numeric keyboard, located on the right side of most keyboards, is a separate set of keys styled like a calculator to use for quickly entering numbers.

Arrow keys, located between the main keypad and the numeric keypad, are used to move the mouse pointer up, down, left, and right on the screen in many kinds of programs.

The insert, delete, page up, and page down keys are used in word processing and other programs for inserting text and objects, deleting texts and objects, and moving up and down through a document one screen at a time.

A25) A mouse is a pointing device. It is used to move a graphical pointer (usually in the shape of an arrow) called a cursor around the screen, or to click on-screen objects (such as a button) to trigger them to perform an action.

A26) The monitor displays information (text and graphics). The screen resolution and dot pitch determine the quality of the display.

A27) The screen resolution and dot pitch determine the quality of the display of the monitor. The screen resolution specifies the number of pixels in horizontal and vertical dimensions of the display device. The resolution can be set manually. The higher the resolution, the sharper and clearer the image.

A28) Pixels (short for “Picture Elements”) are tiny dots that form an image on the screen.

A29) The dot pitch is the amount of space between pixels, measured in millimetres. The smaller the dot pitch the sharper the display.

A30) A dial-up modem is a type of communication device that uses a phone line to dial a phone number to connect to the internet and can transfer data at the speed of up to 56,000 bps (bits per second).

A31) A Digital Subscriber Line (DSL) connection is a type of communication device that also uses a standard phone line, but it can transfer data upto 20 times faster than a standard dial-up modem.

A32) A cable modem is a type of communication device that uses the cable line maintained by the cable company and is generally faster then DSL.

A33) A Network Interface Card (NIC) is a type of communication device that connects a computer to a Local Area Network (LAN). A high speed NIC called 1000BaseT can transfer data at 1000 million bits per second (mbps)

A34) Local Area Networks (LANs) are commonly used to connect computers within a limited area such as a school, a home, or an office

A computer includes both hardware and software. In general, hardware comprises the visible, physical elements of the computer, and software provides the invisible instructions that control the hardware and make it perform specific tasks.

1. Central Processing Unit (CPU)
2. Memory (main memory)
3. Storage Devices (such as CDs and DVDs)
4. Input and Output devices (such as keyboard, mouse (input) and monitor, printer (output)
5. Communication devices (such as modems and Network Interfacing Cards (NICs))

CPU stands for Central Processing Unit

Hertz (hz) is used to measure computer speed.

A computer is nothing more than a series of switches. These switches can exist into two states: on or off. If the switch is on, it’s value is 1. If the switch is off, it’s value is 0. Storing information in a computer is only a matter of turning switches on or off. The 0s and 1s comprise the binary number system and are called bits.

A byte is the minimum unit of computer storage. A byte comprises of 8 bits. A small number such the number 3 can be stored in a single byte. For larger values a series of bytes can be used.

A computer’s memory consists of an ordered sequence of bytes for storing programs as well as data with which the program is working. It is the computer’s work area for executing a program. A program and it’s associated data must be moved into the main memory before the CPU can execute the program.

RAM stands for Random Access Memory.

Every byte in the memory has a unique address. The address is used to locate the byte for storing and retrieving data Since the bytes can accessed at a random order from the memory, the memory is called Random-Access- Memory (RAM).

Computer storage and memory are measured in bytes and its multiples (kilobytes, megabytes, gigabytes, terabytes, etc)

Disk size is measured in bytes.

Memory is volatile; that is, when the power supply to the computer is turned off the data stored in the memory is erased. On the other hand, storage devices permanently store data irrespective of whether or not the device is connected to a power source.