What Is a System

Computer Technology 3200

Unit 1 Notes

What Is a System?

A system is anything that:

Receives input from a source
Performs a process on the input
Provides an output based on the processing
Gives feedback to tell the system whether everything is functioning properly

Systems can be naturally occurring, like a river or our bodies, or they can be man-made, like a car, a toaster or….a computer.

Many systems are made up of several subsystems that do specific jobs. Think of all the subsystems that make up a car (or quadrunner)

So How is a Computer a System?

A computer cannot “think” on its own- it receives input from different sources or components, such as:
the keyboard or mouse
software programs
the operating system (Windows)
the hard drive
a scanner
a digital camera

Then it has to perform a process on the input it gets by using other components like the Central Processing Unit (CPU)

Once the processing has been done, the results need to be sent to specific outputs, like:
the video card and monitor
the printer
the sound card and speakers

Now that we know what a system is, what it does and that a computer is a type of system, we have to answer the following questions:

What are the basic building blocks of data and information?

How does data travel around a computer?

What are the major components of a computer system that are involved in the processing of data and information?
What determines how fast information gets processed?
How is information stored within a computer system?
What are the components of a computer system that are responsible for input and output and how are they connected to the rest of the computer?

The answers to these questions will be found as we examine computer architecture

What Is Computer Architecture?

Definition: Computer architecture is a term that describes the physical and logical layout of the parts of a computer system and how they are connected together:

Physical Architecture: Includes the way the electrical paths are laid out and the number, type and function of the different circuit boards used to move data around the system.

Logical Architecture: Involves the location, transmission and storage of data and the ways in which it is manipulated and transmitted to and from the outside world.

So What Are Some of the Physical Parts of a Computer System?

Power Supply

The power supply takes the 110-volt alternating current (AC) from the wall outlet and converts it into several direct current (DC) voltages for use by various computer components.

The power supply is REGULATED to produce very stable voltages and FILTERED to supply very stable currents. Despite this, computers should be plugged into a SURGE SUPPRESSOR that eliminates any major power fluctuations from the wall outlet.

Voltage: The force that causes electrons to flow
Current: Flow of electrons, measured in amperes
Resistance: The opposition to the flow of electron currents

Chips

Chips refer to tiny pieces of silicon containing thousands of electronic components and their connections referred to as an INTEGRATED CIRCUIT (IC).

The main components in the circuits are transistors, diodes, resistors, and capacitors.

The transistors and diodes constitute electronic switches
The resistors and capacitors control the flow of current.

Chips are housed in plastic cases called DIPs or Dual In-Line Packages. These are either soldered directly into the circuit boards or placed in sockets on the board for easy installation and removal.

Chip circuits comprise the main processor and electronic memory of the computer as well as many other support circuits.

The Motherboard

The motherboard is a resin or plastic board that contains all the chips that form the main electronic circuits of the computer.

These include the:
Microprocessor
ROM memory chips such as the BIOS chip
RAM memory chips
Clock

IC's that connect the CPU to the bus.

The motherboard also contains the parallel conducting paths (bus) that interconnect the chips as well as provide connections to the outside. These paths are printed onto the motherboard as parallel lines of conductors that make it a PRINTED CIRCUIT (PC) board.

Interface Boards

Interface boards are PC boards that plug into the motherboard to control peripheral devices.

Some of the interface cards that are found inside a computer system include:

Sound card: Allows speakers or a microphone to be plugged in
Video card: Allows the monitor to be plugged in
Network card or modem: Allows a computer to communicate with another computer or access the Internet.

Hard Drive

The main source of permanent internal memory in a computer system

One of its major roles is to hold the files that make up the computer’s operating system as well as any other needed programs. Many other files like written documents, music, pictures/graphics and so on, can also be stored.

Ribbon Cables

These wide, gray cables connect the different drives in a computer system to the motherboard.

Processor

Controls all the movement of information from one component to another

Bits and Bytes

Question: What is the basic building block of a computer?

The basic building block of any computer is a switch. These switches can be turned either on or off by an electrical current and can maintain their state until another signal changes it.

In computers a switch represents either 0 (off) or 1 (on). A 1 or a 0 represented by a switch is called a BIT or Binary Digit.

Thus the basic physical building block is a switch and the basic logical building block is a BIT.

What is the difference between digital and analog electronics?

In digital devices such as computers switches are either on or off. Currents either flow or they do not. The size of the current is not important as long as it is within the range that operates the switches properly. Such circuits are called DIGITAL.

In analog circuits the strength of the current is important. The loudness of a speaker in your radio is controlled by the size of the current and in theory at least can be controlled continuously over a set range by a rotary volume control. Such a device is referred to as ANALOG.

What are bytes?

Bits are arranged in groups. A group of eight bits is called a BYTE.

By rearranging the sequence of bits in a byte, 256 different sequences are possible. Thus a byte can contain codes for 256 different things.

The code that is most accepted by computer designers to represent the letters and symbols we communicate with is the ASCII code or American Standard Code for Information Interchange.

In this code a byte or 8 bits represents one character. The ASCII code is used to represent symbols but other codes are used to represent instructions, and numbers inside the computer.

How does a byte represent a character?

Tables of ASCII codes are available in most programming books. Here's how it works:

0100 0001 or decimal 65 represents the letter A

0100 0010 or decimal 66 represents the letter B

....

0101 1010 or decimal 90 represents the letter Z

and so on

Hang on now, what is the decimal number system?

The number system we use everyday is called the decimal system that uses ten digits, 0 to 9.
We also call this the Base 10 system.

The binary number system uses two digits, 0 and 1.
We also call this the Base 2 system.

So how are binary and decimal numbers converted?

Binary / Decimal
0 0 0 0 0 0 0 0 / 0
0 0 0 0 0 0 0 1 / 1
0 0 0 0 0 0 1 0 / 2
0 0 0 0 0 0 1 1 / 3
0 0 0 0 0 1 0 0 / 4
0 0 0 0 0 1 0 1 / 5
0 0 0 0 0 1 1 0 / 6
0 0 0 0 0 1 1 1 / 7
0 0 0 0 1 0 0 0 / 8
0 0 0 0 1 0 0 1 / 9
0 0 0 0 1 0 1 1 / 10

OK, so how did you do that?

Every bit represents a power of 2. Here’s what a byte looks like:

Base 2 / 27 / + / 26 / + / 25 / + / 24 / + / 23 / + / 22 / + / 21 / + / 20
Base 10 / 128 / + / 64 / + / 32 / + / 16 / + / 8 / + / 4 / + / 2 / + / 1 / = / 255

Binary

/ 1 / 1 / 1 / 1 / 1 / 1 / 1 / 1 / = / 255

QUESTION: We said earlier that there were 256 possible sequences, right? So why did the calculation above only add up to be 255?

ANSWER: We need to count zero as a possible value, so there ARE 256 possible sequences:

0-255= 256 possibilities

EXAMPLE: Convert 177 decimal to binary.

A. Write down the eight powers of 2 and put a line under each:

128 / 64 / 32 / 16 / 8 / 4 / 2 / 1
___ / ___ / ___ / ___ / ___ / ___ / ___ / ___

B. Put a 1 under the largest number less than or equal to 177:

128 / 64 / 32 / 16 / 8 / 4 / 2 / 1
1 / ___ / ___ / ___ / ___ / ___ / ___ / ___

C. Subtract that number from the original:

177-128 = 49 (so put a 1 under the 32 now)

D. Repeat steps B and C for the remaining number until it becomes 0:

49-32 = 17 (so put a 1 under the 16), then

17-16 = 1 (so put a 1 under the 1)

128 / 64 / 32 / 16 / 8 / 4 / 2 / 1
1 / ___ / 1 / 1 / ___ / ___ / ___ / 1

E. Fill the remaining blanks with 0's. The binary number in the blanks is equal to the original number.

128 / 64 / 32 / 16 / 8 / 4 / 2 / 1
1 / 0 / 1 / 1 / 0 / 0 / 0 / 1

Final answer: 17710 = 101100012