Introduction to the Computer Hardware and Software

Types of computers Micro mini- and mainframe Differ basically in Size and Speed. Networking of microcomputers (mini and mainframe computers only). Server - stores distributed software and licensing, for shared access to files, as well as secure back-up. Maintenance – Different for all the three types.

Mini computers needs a part-time or full time operator. Microcomputers often have no operator other than the current user, and the maintenance responsibility falls on the user. A computer network requires part- or full- time staff. Micro-computers encompass PDA (personal digital assistant), a smartphone, or a tablet PC, to laptops, desktops. There are two common types of microcomputers: MAC and PC type.

Hardware Components

The CPU CPU stands for “central processing unit” and is actually a microprocessor. Microprocessor is a clock speed in mega- Hertz.

The Display (Monitor) The computer monitor/ screen is called the “CRT”, which stands for "cathode ray tube". “LCD” or liquid crystal display monitors. LCD monitors are thinner, lighter and use less power than the traditional CRT monitor. Screen size is measured on the diagonal. Screen resolution - pixels that can be displayed.

Printers and Scanners Most common types - InkJet and Laser printers. InkJet Printers - transfer an image via magnetic charge.  High quality graphics and a large variety of fonts are available.  Inexpensive to purchase, but more costly to maintain. Laser Printer - the image is produced by scanning a laser beam across an electronically charged drum.  Toner, or ink, having an opposite charge and stuck to the drum, is then transferred to the paper by pressure and heat.  High quality graphics and multiple font printing are readily available. Laser printers tend to be more expensive to purchase and relatively expensive to maintain.

Some commonly used printing terms Buffer Size - storage device inside the printer for stores a portion of the document prior to printing. PPM (pages per minute) describes print speed for inkjet or laser printers (8-12 is good). PCL stands for "printer control language". Developed by Hewlett-Packard, it is a set of fonts and layout instructions. Postscript is a set of fonts and layout instructions originally defined for MacIntosh computers only.

Printers require PRINT DRIVERs. A PRINT DRIVER consists of a program that recodes output from the Software Program to suitable patterns of dots on the paper. Print drivers are written by the software manufacturers (not Printer manufacturers), since the software manufacturers determine the coding table for the output.

Scanners Scanners have become an important method of transferring printed information into digital format in recent years. The basic principle of a scanner is to analyze an image and process it in some way. Scanning of images and text (using Optical Character Recognition or OCR) allow you to save information to a file on your computer. You can then alter or enhance the image, or edit text, and incorporate it into a document or print it out.

Types of Scanners Flatbed scanners, also called desktop scanners, are the most versatile and commonly used home scanners. Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. This model is useful in situations with large volumes of pages to be scanned. Handheld scanners rely on the user to move them instead of a motorized belt. Does not provide good image quality. However, it can be useful for quickly capturing text. These are most commonly seen for scanning bar codes. Drum scanners are used to capture incredibly detailed images, and are most commonly used in the publishing industry.

Quality of scanned images and text depends upon a combination of factors:  Sharpness is a function of the quality of the optics used to make the lens and the brightness of the light source.  Resolution is defined by the number of dots per inch (dpi). The scanner's dpi is determined by the number of sensors in a single row (x-direction sampling rate) by the precision of the stepper motor (y-direction sampling rate).  Software is then used to enhance images. Interpolation is a software process used to increase the perceived resolution of an image. Extra pixels are created in between the ones actually scanned. These extra pixels are an average of the adjacent pixels.

Bits and Bytes – How the Computer Stores Information The mechanics of computer function is an enormous number of "on/off" switches. In actuality, computers know only “on”s and “off”’s. A single "on/off" switch is called a bit. The term “bit” comes from “binary digit”. The digit “1” is assigned to “on”, the digit “0” is assigned to “off”. Bits can be combined to obtain representations for numbers, letters, and special characters. A byte is a combination of 8 bits. There are 28 = 256 combinations of 8 bits, or 256 “characters” that can be represented by 1 byte.

ASCII, Unicode and Hexadecimal Codes ASCII stands for American Standard Codes for Information Interchange. The ASCII codes correspond to assignments of characters or icons (letters, number and symbols) to the 256 switch settings in a byte (8-bits). The ASCII code number is the decimal equivalent of the binary code used for the eight switch settings. ASCII code derives from bits and bytes.

Computer Storage Terminology We consider next how units of bits and bytes of information are used to define storage space on a computer.  One bit represents one "0/1" switch.  One byte represents 23 bits = 8 bits.  After that, we increment bytes by powers of 10. The amount of storage space available on a disk is usually described in terms of bits, bytes, KB, MB, or GB.

RAM, ROM, and Read/Write Storage A major component of the microcomputer is the storage device(s). All microcomputers have systems for getting data into the computer, saving information on the computer, and getting data back out of the computer. Data are stored on disks that may be removable or fixed in the computer.

There are different kinds of storage: 1.Random Access Memory (RAM) 2.Read Only Memory (ROM) 3.Read/Write storage: Hard Disk, Floppy Disk, CD, DVD, Zip disk, plug-in drives Random Access Memory (RAM) is a major component of personal computers. RAM is the fastest storage device, and is accessed at the speed of the microprocessor. Most software has a minimum RAM requirement.

Random Access Memory can be installed on the motherboard (the motherboard is the CPU), or installed in expansion slots in a computer. Limitation of RAM is that it is temporary. When the computer is turned off, the information stored in RAM is lost.

The Hard Drive Information can be stored “permanently” on a hard disk.  a device inside the computer box (most common)  a card in an expansion slot  an external device

CD’s, Diskettes, and Zip Disks CD-ROM stands for "Compact Disk-Read Only Memory. CD-ROM is a storage medium based on laser technology. The storage capacity is large, on the order of one or more gigabytes. CD-R/W stands for Compact Disk-Read/Write. However, once you have written to a CD, it cannot be erased and overwritten like a diskette, unless you buy CD’s designed for rewriting. Even re-writable CD’s are not designed for continual saving and overwriting

DVD (Digital Video Display) drives are a common option on computers. Compact Flash (USB drives), memory sticks and other compact media (e.g., micro SD cards) are increasing versatile and vary in capacity. They are very useful to have and can fit in your wallet or on a keychain. Access Time is the time required by the CPU of the computer to access one byte of information on a device. It is good to have fast access time. The access time is measured in milliseconds.

Modem and Ethernet "Modem" is shorthand for Modulate and Demodulate. It enables two computers to exchange data over standard telephone lines. Use of a modem requires communications software, which performs several functions, among them:  Dialing and redialing  Logging on (connecting) to system being called  Transmission of information. Transmission speed of a modem is Baud rate = # bits that can be transferred in 1 second. The standard for a good, high-speed modem is 56K.

Ports and Cables A port is a physical location through which the computer exchanges information with an external device (e.g., printer or modem). A port has an address so that the computer knows where to send and receive information. Three types of port: parallel and serial ports, and USB.

Software The CPU, storage devices, and other devices in a personal computer communicate with each other via an operating system. Examples of IBM compatible operating systems include UNIX, DOS, and OS2. The DOS operating system was basic for most IBM compatible computers. In the past, as recently as 1996, learning DOS commands to manage files and access to application software was important. Originally, WINDOWS functioned as a layer “above” the disk operating system, though in new versions Windows serves as the operating system.

Windows Windows is a Graphical User Interface (GUI) – a more intuitive way to interact with a computer. Instead of typing a command in DOS, tasks can be performed in an intuitive, visual manner via point and click, with the help of a “mouse” or other input device. Tasks such as copying a file from one disk to another can be accomplished by “dragging” an icon representing the file from the icon representing one disk to the icon of another. A GUI acts as a translator allowing the user and the computer to communicate with each other in a way that is easy for both to understand.

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