Before you start
Objectives: learn which devices are used to input data, to process data and to output processed data so we can use it. Learn what makes computers modular, how computers can communicate and what is the part of software.
Prerequisites: no prerequisites.
Key terms: hardware devices, internal hardware, internal components, software, internal components, processing, data storage, input devices, keyboard, mouse, touchscreen, output devices, monitor, audio, printer, network, modularity.
Hardware versus Software
The first thing to remember is that our PC consist of hardware and software. The PC hardware includes the electronic components that we see when we open up the computer case. The PC hardware, by itself, can’t really do much of anything. Our PC needs something that gives that hardware set of instructions that tell it what to do. This is what the software is used for. PC software can be stored as programs on a hard drive or even stored as programs inside of some special hardware chips on the system itself.
The internal hardware provides three main functions.
First, it provides processing functionality. The main processing unit in our PC is the Central Processing Unit (CPU). Its job is to process data according to a set of instructions. It takes the input and does something with it.
Short Term Data Storage
Second functionality is short term data storage. This is done using Random Access Memory or RAM. RAM is the place where the CPU stores the data it’s currently working on. In addition, the instructions that the CPU is currently using are also stored in RAM. Remember, RAM is not persistent. That means that if we shut down our PC, data that was stored in RAM will be erased. RAM is used for short-term storage because of speed.
Long Term Data Storage
For long-term storage we use a variety of storage mediums. The most important one is the Hard Disk Drive or HDD. It can store bunch of data and it can retrieve it relatively quickly, but not as nearly as fast as RAM. That’s why we don’t use a Hard Drive instead of RAM. Remember, data saved on long-term storage is persistent. That means that if we shut down our PC, the data saved on the Hard Drive will be intact.
There are other types of long-term storage medium as well. One of the older ones which we don’t use a lot anymore is Floppy Disc Drive or FDD. Back in the old days computers didn’t have a HDD, they only had an FDD. We don’t use FDD anymore because they are slow and can’t store a lot of data. The advantage of FDD is that the medium is removable. Another option for long-term storage are optical drives. These include CD as well as DVD drives. With CD or DVD drive we can store huge amounts of information on an optical disc. These optical storage devices come in two different varieties. We have the Read Only version, for example CD-ROM, which means Compact Disk – Read Only Memory. We can read information from that medium, but we can not save new information. The same is with the DVD-ROM drives. However, we have a writable versions as well, like CD-R, or CD-RW. These allow us to both read information from the CD as well write information to it. It is the same with the DVD and Blu-ray drives.
One more type of long-term storage medium is a Flash Drive. Unlike RAM, memory chips used in Flash Drives are persistent. This is great because flash memory is fast and it can store a lot of data.
Let’s take a look at some key components that let us bring some information from the outside and put it inside of the PC. There’s three main sources of input.
The first one is the keyboard. Keyboard allows us to send information to the internal PC hardware by pressing a key. When we press a key on the keyboard, electronic signals are sent through the wire (or ether) into the internal PC hardware where that signal is picked up and sent to the CPU (Central Processing Unit). Before the Personal Computers emerged, data were sent to the CPU using punch cards which ran trough the card reader.
The second important input device is the mouse. Mouse works different than keyboard. Keyboard has a chip that checks which key has been pressed and sends an appropriate code for the particular key to the PC hardware. Mouse has little sensors along with the roller ball. When we move the mouse, the sensors keep track of which direction the ball is rolling and moves the cursor on the screen accordingly. Optical or laser mouse works a little differently but the principle is the same.
The third input device is the touchscreen. When we have a touchscreen we don’t have to use the keyboard or the mouse. Touchscreen applies an overlay on top of the PC monitor. This overlay consist of two layers between which is an empty space. When we press on a particular place on the screen, the first layer gets bent in and touches the second layer, which then sends an electrical signal to the PC hardware consisting of X and Y coordinates of the screen. Software then does what it is programmed to do when we press on particular point on the screen.
To get information out of the PC we need to have output devices connected to it.
The most important output device is a Monitor. Information being processed by the CPU can be displayed on the screen so we can see what we are working with. Monitors were not used as soon as the Computer emerged. Before monitors, we used Punch-cards to input data to to the computer and the results of the processing would be printed on the paper instead of the screen.
The second type of output is audio. Again, today we take audio for granted, but in the beginning computers could not produce audible signals.
The third device that we use to output data from the PC is a Printer. With printers we can print documents or whatever we see on our PC monitor. Printer takes information from the PC and using a variety of different technologies prints the formatted information onto a piece of paper.
Another thing that we have to mention is how multiple computers can communicate together. That’s done using a computer network. A special interface is installed on each computer and we connect them together using a predefined type of wire or radio signal. This way, information processed on one computer can be sent to another computer on the network. Network acts as both input and output medium.
The great thing about modern PC system is the fact that it is modular. All PC components that we talk about are built on a modular basis and are standardized. That means that we can add or remove components to customize our PC or to replace bad parts. Standards allows us to buy different components from a variety of different manufacturers, put them all together into a system and have them interoperate correctly.
The PC hardware, by itself, can’t really do much of anything. Our PC needs something that gives that hardware set of instructions that tell it what to do. This is what the software is used for. The internal hardware provides three main functions: processing, short term and long term data storage. The main processing unit in our PC is the Central Processing Unit (CPU). Short term data storage is done is done using Random Access Memory or RAM. For long-term storage we use a variety of storage mediums. The most important one is the Hard Disk Drive or HDD. There’s three main sources of input: keyboard, mouse and touchscreen. The most important output devices are: monitor, audio device and printer. Computers can communicate using computer network. All computer components are standardized and because of that modern PC systems are modular.