OEA FREE COMPUTER COURSES
"Who controls the past commands the future. Who commands the future conquers the past."
Computer
An electronic device that has the ability to store, retrieve, and process data, and can be programmed with instructions that it remembers.
The physical parts that make up a computer (the central processing unit, input, output, and memory) are called hardware.
Programs that tell a computer what to do are called software.
WHAT A COMPUTER DOESThe instructions in the program direct the computer to input, process and output as follows:Input/OutputThe computer can selectively retrieve data into its main memory (RAM) from any peripheral device (terminal, disk, tape, etc.) connected to it. After processing the data internally, the computer can send a copy of the results from its memory out to any peripheral device. The more memory it has, the more programs and data it can work with at the same time.StorageBy outputting data onto a magnetic disk or tape, the computer is able to store data permanently and retrieve it when required. A system's size is based on how much disk storage it has. The more disk space, the more data is immediately available.PROCESSING(The 3 C's*)Once the data is in the computer's memory, the computer can process it by calculating, comparing and copying it.CalculateThe computer can perform any mathematical operation on data by adding, subtracting, multiplying and dividing one set with another.CompareThe computer can analyze and evaluate data by matching it with sets of known data that are included in the program or called in from storage.CopyThe computer can move data around to create any kind of report or listing in any order.By calculating, comparing and copying, the computer accomplishes all forms of data processing. For example, records are sorted into a new order by comparing two records at a time and copying the record with the lower value in front of the one with the higher value.The computer finds one customer out of thousands by comparing the requested account number to each record in the file. The dBASE query statement: SUM SALARY FOR TITLE = "NURSE" causes the computer to compare the title field in each record for NURSE and then add (calculate) the salary field for each match.In word processing, inserting and deleting text is accomplished by copying characters from one place to another.Remember The 3 C'sIf you wonder whether the computer can solve a problem, identify your data on paper. If it can be calculated, compared and copied on paper, it can be processed in the computer. The 3 C's - Finding Things The example above counts all California records in the database by comparing each record with "CA." Every record in the database is read into memory. The memory locations that state is written into are compared with the letters "CA" in the program. If they are equal, a "1" is added to the California counter. The second record is written into the same memory bytes as the first record, and the field is compared again. This process is performed until the last record has been examined. The 3 C's - Displaying and Printing Data is stored as contiguous fields in the database. There are no blanks in between. The data is displayed and printed the way we like to see it by writing the data into memory and copying the characters into the desired order. The date in this example is printed through a "picture," which is a set of characters that acts as a filter. Each character in the date is compared to a corresponding character in the picture, and the one copied as output is determined by the rules. Pictures can be implemented in software or in hardware. The 3 C's - Sorting Sorting, or resequencing, data is accomplished by comparing each item of data with the others and copying it into the appropriate order. Of course, there's a ton of calculating going on to keep track of what's being compared. Years ago, when databases were stored on tape, the speed of a vendor's sort program was a powerful marketing feature. All transactions had to be sorted into account number sequence in order to be processed. In today's online systems, data is often indexed. Instead of sorting the actual data records themselves, the much smaller indexes are sorted. The 3 C's - Editing The magic of word processing is really nothing more than copying the text in memory. In this example, if you want to insert a character into an existing line, the remaining characters are copied one memory location (byte) to the right so there is room for the additional letter. Deleting is just copying in reverse. As in all data processing, there is a whole lot of calculating and comparing going on to keep track of where the text is stored in memory.THE STORED PROGRAM CONCEPTThe computer's ability to call in instructions and follow them is known as the "stored program concept." Instructions are copied into memory from a disk, tape or other source before any data can be processed. The computer is directed to start with the first instruction in the program. It copies the instruction from memory into its control unit circuit and matches it against its built-in set of instructions. If the instruction is valid, the processor carries it out. If not, the computer comes to an abnormal end (abend, crash).The computer executes instructions sequentially until it finds a GOTO instruction that tells it to go to a different place in the program. It can execute millions of instructions per second tracing the logic of the program over and over again on each new set of data it brings in.As computers get faster, operations can be made to overlap. While one program is waiting for input from one user, the operating system (master control program) directs the computer to process data in another program. Large computers are designed to allow inputs and outputs to occur simultaneously with processing. While one user's data is being processed, data from the next user can be retrieved into the computer.It can take hundreds of thousands of discrete machine steps to perform very routine tasks. Your computer could easily execute a million instructions to put a requested record on screen for you.
GENERATIONS OF COMPUTERS
First-generation computers, starting with the UNIVAC I in 1951, used vacuum tubes, and their memories were made of thin tubes of liquid mercury and magnetic drums.
Second-generation systems in the late 1950s replaced tubes with transistors and used magnetic cores for memories (IBM 1401, Honeywell 800). Size was reduced and reliability was significantly improved.
Third-generation computers, beginning in the mid-1960s, used the first integrated circuits (IBM 360, CDC 6400) and the first operating systems and DBMSs. Online systems were widely developed, although most processing was still batch oriented using punched cards and magnetic tapes.
Starting in the mid-1970s, the fourth generation brought us computers made entirely of chips. It spawned the microprocessor and personal computer. It introduced distributed processing and office automation. Query languages, report writers and spreadsheets put large numbers of people in touch with the computer for the first time.
The fifth generation is becoming visible with more widespread use of voice recognition and natural and foreign language translation. Higher-speed machines combined with more sophisticated software will enable the average computer to talk to us with reasonable intelligence sometime in the 2010-2015 time frame.
(Central Processing Unit)
The CPU controls the operation of a computer. Units within the CPU perform arithmetic and logical operations and decode and execute instructions. In microcomputers, the entire CPU is on a single chip.
Monitor
Also called a display. A device that displays text and graphics generated by a computer. Desktop monitors are usually cathode-ray tubes, and laptop monitors are usually liquid crystal display. A monitor can be monochrome (black and white) or color. Color monitors may show either digital or analog color.
Keyboard
A set of keys for computer input, which resembles a typewriter keyboard, but with a few extra keys for computer commands and usually a numeric keypad added. The original typewriter keys worked mechanically to make a metal hammer with a raised, inked type character on it strike a page. On a computer keyboard, hitting on a key sends an electrical signal to a microprocessor, which sends a scan code to the computer's basic input/output system.
Keyboard keys
The buttons on a keyboard that are pressed with a finger to input characters.
101-key keyboard
A standard computer keyboard with 101 keys including the alphanumeric keys, the number pad, F keys, and arrow keys.
104-key keyboard
A keyboard with 104 keys designed to accommodate the Windows 95 operating system.
AT keyboard
Advanced Technology keyboard. The keyboard that originally came with the IBM PC/AT computers, which had 84 keys including the alphanumeric keys, the number pad, F keys, and arrow keys.
AZERTY keyboard
The first six letters in the keyboard layout used in some European typewriters..
Chiclet keyboard
A keyboard with small, square keys.
Dvorak keyboard
A keyboard designed to make typing more efficient, using a different arrangement of letters than the QWERTY keyboard so that the letters used most frequently are all together on the main line of keys. The problem with converting to the Dvorak keyboard is that it would require all typists to relearn how to type
Keyboard buffer
A memory area that stores keystrokes when a typist is too fast, to allow the program to catch up.
Keyboard commands
Commands given by pressing keys on the keyboard; most keyboard commands require two keys pressed at once, and some require three or four keys pressed at once. For example, control-B, alt-G, command-shift-I.
Keyboard key
Each part of a keyboard that is pressed with a finger to input a character.
Keyboard shortcut:A key combination that can be pressed to do a task, instead of using the mouse to select a pull-down menu option. Keyboard shortcuts can be found in the pull-down menus, where they appear next to the commands. A commonly used keyboard shortcut in Windows or Macintosh is Control+S, which is a quick way to save a file.
QWERTY keyboard
The standard typewriter or computer keyboard. The arrangement of letters originally was designed to keep fast typists from jamming the old mechanical typewriters; frequently used keys are separated from each other. With modern keyboards there are no longer jamming problems. An alternative keyboard called the Dvorak layout was designed which has the most frequently-used keys all on the center line for faster typing, but the qwerty keyboard continues to be used because so many typists know it.
RAM
(Random Access Memory)
The working memory of the computer. RAM is the memory used for storing data temporarily while working on it, running application programs, etc."Random access" refers to the fact that any area of RAM can be accessed directly and immediately, in contrast to other media such as a magnetic tape where the tape must be wound to the point where the data is. RAM is called volatile memory; information in RAM will disappear if the power is switched off before it is saved to disk.
Modem
A peripheral device that connects computers to each other for sending communications via the telephone lines. The modem modulates the digital data of computers into analog signals to send over the telephone lines, then demodulates back into digital signals to be read by the computer on the other end; thus the name "modem" for modulator/demodulator. Modems are used for sending and receiving electronic mail, connecting to bulletin board systems, and surfing the Internet.
Cable modem
A cable modem is an external device that hooks up to your computer and instead of getting an internet connection through your telephone wire (or another system), you get a connection through your cable network (same place your cable TV connection comes from).
External modem
A modem that is outside the computer case; a separate unit that is plugged into the serial port.
Fax/modem
A combination fax and data modem, which is either an external unit, that plugs into the serial port or an expansion board that is installed internally. A faxmodem makes it possible to fax a document straight from the computer, but cannot scan documents, which are not in the computer. Most modems now are faxmodems.
Internal modem
A modem that is inside the computer, connected by plugging into an expansion slot
Motherboard
The main circuit board inside a computer, which contains the central processing unit, the bus, memory sockets, expansion slots, and other components.Additional boards, called daughter boards, can be plugged into the motherboard.
DOS
Disk Operating System.More computers worldwide have DOS than any other operating system.There are different versions of it: PC-DOS for IBM PCs, MS-DOS for non-IBM PCs, plus Apple DOS, Amiga DOS, Novell DOS, etc.
MS-DOS
Microsoft Disk Operating System.A personal computer operating system from Microsoft, which is similar to IBM's PC-DOS.It is a single user system that runs one program at a time because of limited memory. Add-on memory boards can expand DOS capabilities.See also DOS.
Computer hardware
The hardware is the physical part of a computer system; the machinery and equipment. Software means the programs that tell the computer what to do.
Computer software
Software is the programs that tell a computer what to do. Hardware is the physical part of a computer system; the machinery and equipment.
Desktop computer
A computer that is small enough to sit on a desktop.
Digital computer
A computer that operates on data which is represented as binary digits (0s and 1s).All commonly-used computers are digital.
MP3
MP3 stands for Motion Picture Experts Group, Audio Layer 3.A popular music download format. MP3 produces CD-quality music in a compressed file that can be transferred quickly, and played on any multimedia computer with MP3 player software. The technology creates sound files a tenth the size of standard CD music files with very little loss of sound quality.
Software
Instructions for the computer. A series of instructions that performs a particular task is called a "program." The two major categories of software are "system software" and "application software." System software is made up of control programs such as the operating system and database management system (DBMS). Application software is any program that processes data for the user (inventory, payroll, spreadsheet, word processor, etc.).
A common misconception is that software is data. It is not. Software tells the hardware how to process the data.
Software is "run."
Data is "processed."
Data
(1) Technically, raw facts and figures, such as orders and payments, which are processed into information, such as balance due and quantity on hand. However, in common usage, the terms data and information are used synonymously.
The amount of data versus information kept in the computer is a tradeoff. Data can be processed into different forms of information, but it takes time to sort and sum transactions. Up-to-date information can provide instant answers.
A common misconception is that software is also data. Software is executed, or run, by the computer. Data is "processed." Software is "run."
(2) Any form of information whether in paper or electronic form. In electronic form, data refers to files and databases, text documents, images and digitally encoded voice and video.
(3) The plural form of datum.
Computer system
The complete computer made up of the CPU, memory and related electronics (main cabinet), all the peripheral devices connected to it and its operating system. Computer systems fall into two broad divisions: clients and servers. Client machines fall into three categories from low to high end: laptop, desktop and workstation. Servers range from small to large: low-end servers, midrange servers and mainframes.
A computer system is sized for the total user workload based on (1) number of users sharing the system simultaneously, (2) type of work performed (interactive processing, batch processing, CAD, engineering, scientific), and (3) amount of storage. Following are the components of a computer system and their significance.
PLATFORM
The hardware platform and operating system determine which programs can run on the computer. Every application is written to run under a specific CPU and operating system environment. The most widely used platform means more software is available for it.
INPUT/OUTPUT
A server's input/output (I/O) capacity determines the number of simultaneous users that it can support at terminals or PCs.
NUMBER OF CPUs
The more CPUs, the more processing that can take place at the same time. High-end servers often contain multiple processors.
CLOCK SPEED
The megahertz rate of the CPU determines internal processing speed. See MHz.
DISK AND MEMORY
A computer system's disk capacity determines the amount of information immediately available to all users. Its memory capacity determines how many applications can be efficiently run at the same time.
