Exploring Computers Article

 Glossary of Terms

Hardware and Software

    Computers are made up of hardware and software.  Hardware is the tangible, physical equipment that can be seen and touched.  Examples of hardware are things such as the keyboard, printer, monitor, and computer chips.

  Software is a package of instructions that tell the computer what to do also known as an application or short for app.  Software are things such as

Microsoft Word, Windows, Sim City, or Google Chrome.  People who write software (instructions that tell the computer what to do) are called programmers or coders.

    Programmers write instructions, or programs, to the computer so that it is able to execute a task or operate properly.  A program can be defined as a series of detailed step-by-step instructions that tell the computer precisely what actions to perform. Many people are making money writing apps (or programs) for the I-phone and Android phones.

    Many people believe that computers can do just about anything and that their level of sophistication requires a genius to program and run them.  In reality, computers are very simple devices that can perform basically only four functions.  A computer can (1) store data and software instructions (programs), (2)

follow a set of steps or commands, (3) do simple and complex arithmetic calculations, and (4) perform logical comparisons.  What makes the computer such a powerful device, given only these four basic functions, is its tremendous speed, its accuracy, and its ability to store vast volumes of data.

Memory – Chips (internal) – thumb/Flash Drives (external)

    The computer must be given instructions (code), in the form of software (program), which tell it exactly what to do.  The instructions that the computer follows are stored in locations known as memory.  For simplicity purposes think of memory in two categories:
(1) The computer’s Internal memory  (ex. microchips: RAM, ROM)
(2) The computer’s External memory  (ex. thumb drives, hard drives, cloud storage: ie. Dropbox)

    The computer’s Internal memory which is composed of computer chips is divided into two types:  RAM (random-access memory

) and ROM (read-only memory).  RAM’s primary purpose is to temporarily store programs given to it by a programmer or operator of the computer.  This type of memory is temporary because it is erased when the computer is turned off (powered down).  In other words, all the information in RAM is erased when the computer is turned off.  It is called random access because  the processor can jump directly form one location to another in random order as the program is needed.  RAM holds programs such as  Microsoft Office, browser software like Chrome, and Internet Explorer or whatever program the computer is currently running.  It make the computer run fast when the program is stored in RAM and not on the hard drive.  This is why it is very important to always buy a computer with plenty of RAM to ensure your computer runs at a fast speed.

    ROM’s primary purpose is to store important instructions that the computer will reuse over and over such as what to do when the computer is turned on and how to control specific requests made by the computer.  ROM is permanent memory that can not be changed or erased.  This is why it is called Read-Only Memory.

Input and Output devices

  A hardware device which enables the computer to accept data is called an input device.  The most common example of an input device is a keyboard.  Other commonly known input devices include a mouse, bar-code scanner, camera, stylus pen, touch display screen, and speech recognition device.

    A hardware device which reports computer information in a form we can understand is called an output device.  The two most common forms of output devices are monitor, and printer.  Other examples include sound or music speakers or earbuds.

Processors
    All computers do processing by following a series of instructions in a software program.  The computer chip that receives and carries out these instructions is called the processor.  All computer systems, regardless of size or manufacturer, have processors (also referred to as central processing units or CPU).

    The processor performs many different functions.  It receives and temporarily stores instructions as well as the data to be processed.  It moves and changes stored data.  It does arithmetic calculations.  It makes decisions of logic, such as determining if two numbers are equal.  It directs the action of the input and output devices.   The CPU is often referred to as the brains of the computer system.

External Storage

    Nearly all general-purpose computers include the ability to connect to additional storage devices that hold data outside the memory of the computer.  These additional storage devices are known as external storage.  External  storage devices are on-line to the computer; that is, they are connected directly to the computer.  They are, therefore, under the control of the processor and can be used at all times.  The most common form of external storage is a thumb drive (aka… USB flash drive).    Other forms of external storage

include hard drives and CD/DVD (recordable) drives.  Now the most commom form of external storage is cloud storage where all the data is stored on servers connected to the internet.

A flash drive can hold as little as 2 GB (gigabytes) to 32 GB (gigabytes) of memory where one CD can store 700 MB (megabyte).  A single layer DVD can hold 4.7 GB (gigabytes of memory).  Hard drives can hold even more.  Most hard drives hold between 250 GB (gigabytes) to 1000 GB (or 1 tarabyte).  Without external storage, one would not be able to back up their computer or be able to travel easily from one location to another with data.
 

The Computer’s World

    To help you understand how the computer works, imagine that each character is represented inside the computer by a series of electronic switches.  In many ways, these electronic switches can be compared to the light switches in our home.  A light switch can be in only one of two states: on or off.  The circuits inside the computer can be thought of in much the same way as the light switches.  The electronic switches can be either on or off.  Since on and off represent only two conditions the computer understands, it is impossible for the computer to communicate the way we do with words.  All it knows is an electrical state of on and off.  Isn’t that incredible considering what a computer can do?  But you ask, we have lots more numbers than 0 and 1 and many more than just 2 words.  You see, numbers and words are instead converted into binary numbers.  Binary means “consisting of two things”, so a binary number is made by using only two digits, 0 and 1.  The number 0 represents “off” to the computer and the number 1 represents “on” to the computer.  Much of the world’s number system is based on the 10 system but the computer’s system is based on the Binary system.  Therefore the binary number system is the only coding system the computer actually understands.

    Imagine eight on/off switches grouped inside the computer.  Each switch (0 or 1) is called a bit.  The on switch is like a light being turned in the on position.  The computer represents it as the number 1.  The off position is represented by the computer with the number 0 (zero).  It takes eight switches (Bits) to store one character (letter, symbol, or space).  As shown below 01010011 is the way the computer understands the letter S.   It sure does take a lot of switches to type one letter on the computer.  Luckily for the computer that it operates at the speed of light which is 186,282.397 miles per second.

A combination of eight switches (bits)  is called a byte in computer terminology.  The computer groups eight bits together to form a byte because it has proven to be a good combination for the computer to handle.

    By using eight bits to turn various switches on and off, there are 256 different combinations possible.  In the binary number system, there can be as many 0’s and 1’s as needed within the eight switches to represent a particular number.  Each 0 can be thought of as representing a switch that is turned off, while each 1 represe

nts a switch that is turned on.

    Each time a key on a keyboard is struck, a binary number is generated in the computer via electronic signaling (see example above).  Inside the computer, the binary number is stored in a memory chip.  All data inside the computer is represented by the use of binary numbers.

    We have now learned that the processor and memory (both ROM and RAM) are made up of electronic circuits that represent information by turning switches off and on.  And we learned that eight switches or bits make up a byte and each byte can store one character of data.

The basic measurement of memory for a PC (Personal Computer) memory is measured in bits and bytes.  A single byte is made up of a series of 1’s and 0’s normally traveling in pairs of eight.  These eight 0’s and 1’s are the way the computer communicates and stores information.  With each keystroke or character a byte of memory is used.

Here is another way of looking at the measurement of memory: 

Directions:  Copy this table into your document.

If we were to key in the name Ernest Grover, it would take thirteen (13) bytes to store the name in RAM.  The one space between the first and last name would require one byte, and the  (12) twelve letters of the name would require twelve bytes.
 

    E     r       n        e      s       t                G       r       o       v      e        r    =13 bytes-used
 

    Computer manufacturers express the capacity of memory in terms of bytes.  Remember it takes 1000 bytes to make a kilobyte or KB. K is short for Kilo and B is short for bytes, which means 1024 bytes of computer memory.  Some of the first personal computers had 64K of memory (RAM).  This meant that the computer had approximately 64,000 bytes of memory and had the capacity to store up to 64,000 characters during processing in RAM.  Today this is would be a ridiculously low amount of memory.  Many disks, hard drives, and CDs can store hundreds, thousands, and even millions more memory than the RAM chips in a computer.  For example a normal CD holds up to 700MB of information (or 700,000,000 million bytes) and an average hard drive can hold 500GB which is 500,000,000,000 (billion) bytes.  If a MB (megabyte) is 1 million bytes then 1 GB (gigabyte) is a billion bytes and some hard drives are now even 1 terabyte which is 1 trillion bytes or 1000 billion bytes of memory.  Wow… now that is a lot of memory.  Many mp3 players can only hold 32 GB worth of music but even that is a lot of songs.