Class Notes

Computer Hardware

Categories of Computers

Mainframes- Very large powerful computers. These computers are very expensive. They are usually connected to terminals which resemble small computers and allow many people to use the same computer (the mainframe). This is called timesharing The largest and fastest mainframes are known as supercomputers.

Minicomputers- Computers in introduced in 1965. They were smaller and less costly. It was not as powerful as the mainframe but was affordable to  small businesses and school districts. They operate 3 to 10 times faster than microcomputers. They are not as popular as they used to be.

Microcomputers- Also known as personal computers (PCs) became popular in the mid 1970s. They were less costly, more powerful and smaller than the minicomputers. Their price allowed everyday people to own a computer. Today, the microcomputer is small enough to fit on a desk or in a briefcase. A notebook or laptop microcomputer is smaller and lighter than desktop microcomputers and can use power from an electrical outlet or rechargeable batteries. Although they are smaller in size notebook computers generally cost more than am equivalent desktop microcomputer because miniature components cost more. Notebook, laptop, and desktop computers are all in this category.

Hardware

Consists of the actual physical, tangible components of the computer. They are divided in 3 basic components: Central Processing Unit, Primary Storage Unit, and Peripheral Devices.

(input) Peripheral Devices ----> (processing) CPU and Primary Storage Unit ---->(output) Peripheral Devices

CPU - The "brain" of the computer. It performs processing functions. It is composed of 2 major components: the control unit and the arithmetic logic unit (ALU). The control unit is in charge of the activities of the CPU. It basically directs or tells the computer what to do. The ALU performs mathematical computations such as *, /, +, -, and < , >, =. The CPU is contained on a single chip called a microprocessor also known as an integrated circuit. The speed of a microprocessor is determined in clock speed, which is measured in megahertz ( MHz), millions of cycles per second. The higher the faster. ex. 100 MHz Pentium

 PRIMARY STORAGE UNIT- is also known as main memory, primary memory, or internal storage. There are two types of chips that take care of a computers internal memory, ROM and RAM chips. ROM is read only memory. ROM is nonvolatile memory because it does not disappear when the computer is turned off. ROM chips store information permanently in the computer's memory, this information supplies the computer with a list of operating instructions. RAM is random access memory. Information on RAM chips can be modified. Users can read, write, and erase its information. RAM is known as volatile memory because it is temporary. When an individual turns off the computer, he loses the information in RAM. RAM, also known as main memory, is the "working memory" of the computer. Its temporary storage. It stores program data while we are working with that program. A program must be loaded into RAM in order to work. Computers typically now come with 16 MB (megabytes) of RAM. The more MB, the better.

PERIPHERAL DEVICES- Devices that are connected to the computer under the microprocessor's control. It includes input devices, output devices, secondary storage, and input/output devices.

INPUT DEVICES

keyboard- is an input device which is similar to a standard typewriter, but it includes extra keys such as the function keys and a numeric keypad.

mouse- an input device. It is usually a palm sized box with two buttons. As you push and pull the mouse along a surface, a pointer moves on the computer screen. It is effective for selecting items.

lightpen- an input device. It looks like a pen attached to the computer by a cable. The user enters input by drawing on the screen.

trackball- an input device. a device which looks like a box with buttons and a ball inside it. The user rolls the ball to move a pointer on the screen.

trackpad- an input device. a pressure sensitive pad with buttons. When you press your finger on it and move it, the pointer moves in the direction you move your finger.

joystick- an input device. a small box with a moving stick and buttons.

touch screen- an input device which lets you touch the screen to make selections.

bar-code reader- input device allows the user to run an optical wand over a barcode and interpret information.

scanner- an input device which transforms images into electronic images.

OUTPUT DEVICES

Printer- an output device. It allows the user to keep permanent records by producing a printout or hardcopy of information. A dotmatrix printer uses tiny dots of ink to produce text and graphics. An inkjet printer sprays tiny dots of ink on a paper to produce text and graphics. A laser printer uses laser beams to bond a substance called toner to the paper.

Monitor- an output device. a tv like screen which uses cathode ray tube technology. Notebook computers use liquid crystal displays.  Monitors have higher resolutions than regular television sets.

SECONDARY STORAGE- receives data from RAM and writes it on a storage medium such as a disk. This data can then be read later and sent back to RAM. It provides long term memory. Remember a computer can not execute a program unless it is first copied into RAM.

Hard disk drive- secondary storage. A hard disk drive is usually built in to most computers. It allows for the fastest access to data. It also allows for huge amounts of data to be saved. A hard disk consists of a sealed chamber inside the computer which holds several disk platters. Information is stored, read, and written on these disk platters.

floppy disk drive- secondary storage. A floppy disk drive is usually built into most computers. The actual disk to be used is not built in to the computer. Most computers now use a 3 1/2 inch floppy disk. The floppy disk is inserted in the disk drive and information can then be stored, written, and read from it. A floppy disk actually holds a disk inside its protective plastic jacket. The disk rotates inside the disk drive when it is being accessed.

CD-ROM disk drive- secondary storage. compact disc read only memory disk drive. A cd-rom disc can only be read. you cannot write on them. cd-rom discs can hold a great deal of data. They can hold 400 times as much data as a 3 1/2 inch floppy disk.

INPUT/OUTPUT DEVICES

modem- an input/output device. short for modulator/demodulator. A modem allows 2 computers to communicate with each other via telephone lines. It modulates digital signals from the computer to analog signals for transmission over phone lines then demodulates transmission from analog back to digital signals. The speed in which a modem can do this is called the baud rate. Many new computers have a baud rate of 33.6 KBPS (kilobits per second. )

 Study Guide

1. What is a mainframe?
2. What is timesharing?
3. What are the largest and fastest computers called?
4. Which computers were introduced in 1965?
5. Which computers became popular in the mid-1970's?
6. What is more expensive a desktop computer or notebook computer?
7. What is the definition of hardware?
8. Hardware is divided into 3 components, what are they?
9. What are the 2 components of the CPU?
10. What unit is in charge of the CPU's activities?
11. What unit does the math for the CPU?
12. The speed of the microprocessor is measured in what?
13. The Primary storage unit consists of what two types of chips?
14. ROM stands for?
15. RAM stands for?
16. Is ROM permanent or temporary memory?
17. Is RAM permanent or temporary memory?
18. What is the definition of a peripheral device?
19.  Is a keyboard an input device, output device, or input/output device?
20. Is a mouse an input device, output device, or input/output device?
21. Is a lightpen an input device, output device, or input/output device?
22. Is a trackball an input device, output device, or input/output device?
23. Is a trackpad an input device, output device, or input/output device?
24. Is a joystick an input device, output device, or input/output device?
25. Is a scanner an input device, output device, or input/output device?
26. Is a printer an input device, output device, or input/output device?
27. Is a monitor an input device, output device, or input/output device?
28. A hard disk drive consists of a sealed chamber inside the computer which holds what?
29. A floppy disk drive is primary or secondary storage?
30. A CD-ROM stands for?
31. Modem is short for what?
32. The speed of a modem is measured in what?
33. A laser printer uses a laser to bond what to the paper?
34. A notebook computer uses what type of display?
35. The f1 to f12 keys are what keys?
36. What printer sprays tiny dots of ink?
37. What kinds of a signals does a modem translate?
38. What is known as the brain of the computer?
39. The projector in our room, e-210, is what kind of device?
40. The Smartboard in our room, e-210, is what kind of device?