Transcript Second module: Inside the computer

2nd Module
• Inside the computer (processor / motherboard / memory).
•Computer’s function (digital vs. binary / bits, bytes / operating
systems).
http://www.learningwithmaria.com/computing
“Learning more on internal hardware”.
Last week we learnt to define a computer and about its main
parts: hardware and software . This week we are going to focus on
the main parts of hardware inside a computer that allow the
information to be processed, the interaction between software
and hardware and the data to be read or stored.
These main parts are:
CPU: the 'brain' of the computer.
Motherboard: where all the components in a computer plug into.
Memory: RAM, cache and ROM.
“Central Processing Unit”.
This is where all the searching, sorting, calculating and
decision making takes place.
On personal computers and small workstations, CPUs are
housed in chips called microprocessors (a silicon chip
composed of tiny electrical switches called transistors).
Its speed is measured in either Megahertz (MHz) or more
commonly now in Gigahertz (GHz). A 1 MHz CPU can carry out
one million instructions per second. A 3 GHz CPU can carry
out 3 billion instructions per second!
“Its components”.
To fully understand all the functions of a CPU, let’s study them in
parts:
•Control Unit
•Immediate Access Store
•Arithmetic and Logic Unit (ALU)
“The Control Unit”.
It executes the instructions you give to your computer.
It controls and monitors the hardware attached to the system to make
sure that the commands given to it by the application software are
used. For example, if you send something to print, the control unit will
keep a check that the instructions are sent to the printer correctly.
It controls the input and output of data so that the signals go to the
right place at the right time.
It controls the flow of data within the CPU.
“The Immediate Access Store”.
It holds the data and programs needed at that instant by the
Control Unit.
The CPU reads data and programs kept on the backing storage
and stores them temporarily in the IAS's memory.
There are two types of IAS: RAM and cache memory.
The CPU needs to have IAS because backing storage (e.g. the
hard disk) is too slow to be able to run the applications from it
directly.
“Arithmetic and Logic Unit”.
This is where the computer processes data either by
manipulating it or acting upon it. It consists of two parts:
•Arithmetic part - which does exactly what you think it should it performs the calculations on the data e.g. 3 + 2 = 5
•Logic part - this deals with logic and comparisons. For example,
it works out if one value is greater, less than or equal to another.
“Central circuit board”.
It is where all of the components and peripherals plug into.
The job of the motherboard is to relay information between the
components and peripherals.
The motherboard houses the ROM and the RAM chips, the CPU,
the graphics card, sound card, network interface card, hard disk
and various other external ports and peripherals all attach
directly to it.
“An image”.
“ROM, Read Only Memory”.
Data stored in ROM is not erased when the power is switched
off - it is permanent. This is called 'non volatile memory'.
ROM is used to hold data that cannot be changed by the user.
Instructions related to the hardware are stored in ROM chips.
An example of a ROM chip is the BIOS (basic input/output
system) which is used when the system boots up.
This data will usually be the software that tells the computer
how to load the operating system when it is switched on or rebooted.
“RAM, Random Access Memory”.
In contrast to ROM, RAM is volatile memory. The data is held
on a chip, but only temporarily. The data disappears if the
power is switched off.
Have you ever forgotten to save your work before the
computer crashed? When you log back on, your work has
disappeared. This is because it was stored in RAM and was
erased when the PC was switched off. However, if you had
saved your work, it would have been transferred from RAM to
the hard disk where it would have been stored safely.
“In terms of speed and size”.
Most data is stored on the hard disk. When we use that data, it is
loaded into RAM because it is much faster to access the data from
RAM than from the hard disk.
When we looked at the 'immediate access store' earlier, we found
out that the CPU needs to access data very quickly. Although
RAM is faster than the hard disk, it still isn't fast enough to cope
with the speed that the CPU needs to deal with data.
The next memory we are going to see, cache, is faster.
“Cache”.
The cache is a special type of computer memory which can be
accessed much faster than RAM. The CPU looks in the cache for
the data it needs. If the data is there, it will retrieve it and process
it. If the data is not there, then the CPU accesses the system
memory and then puts a copy of the new data in the cache before
processing it.
Cache memory is volatile i.e. when the computer is shut down,
the data stored there is lost.
“Digital vs. Binary”
We get the information that the computer has processed in
digital form (Text, numbers, pictures, audio, and nearly any other
form of information). However, the computer can only think in
binary (using binary digits each of which has a value of 1 or 0).
User
Application (information in digital form)
Compiled runtime language (BASIC, C#)
ASM (assembly language)
Computer process to
Binary
translate into binary
Computer
“Bits and bytes: binary units”
A binary number is either a zero or a one and is known as ‘bit’
(binary digit).
However, the CPU cannot deal with just one bit at a time, it is
just too small. It usually deals with 8 bits at a time, which is
known as ‘byte’.
11100101 is a byte, or any other combination you can think of
which contains 8 digits consisting of zeros and ones.
“Bits and bytes: ASCII code”
Why does all this matter? We often need to process words, so
the computer must be able to store letters and other keyboard
characters. This is done by making up a code where each number
represents a character.
One common code is A=65, B=66 and so on. This is called ASCII
code (American Standard Code for Information Interchange).
Each ASCII character occupies just one byte. The eight bit binary
code or byte which represents the letter A is 01000001. Here you
can check the alphabet in binary code.
“Bits and bytes: storage and speed”
8 bits make 1 byte. Each keyboard character takes 1 byte of memory.
1000 keyboard characters = 1000 bytes or 1KB (kilobyte). In reality,
it is really 1024 bytes which make a kilobyte, but generally people
refer to 1000 bytes as a kilobyte.
1000 kilobytes = 1MB (megabyte) = 1,000,000 keyboard characters.
(1,048,576 bytes). A CD ROM has a capacity around 700MB.
1000 megabytes = 1GB (gigabyte) = 1 billion characters (1,073,741,824).
A DVD can hold from 4.7 GB of data up to 17.08GB (double-sided and double layered).
“Definition and characteristics”
An operating system is software consisting of programs and
data that runs on computers, manages computer hardware
resources, and provides common services for execution of
various application software.
It is the most important type of system software. It acts as
intermediary between application programs and the computer
hardware.
Examples of popular modern operating systems
are: BSD, Linux, Mac OS X or Microsoft Windows
“Some screenshots”
DOS (Disk Operating System)
Proprietary Software
Linux (Ubuntu)
Free open source software
“Some screenshots”
DragonFly BSD
“Some screenshots”
Mac OS X Lion
“Some screenshots”
Windows 7
“Conclusion”
In this second module we have seen:
How a computer is organized internally: CPU (divided into central
unit, immediate access store and arithmetic and logic unit),
motherboard and its main memories (ROM and RAM).
http://computer.howstuffworks.com/cpu-quiz.htm
A main function of the computer: transforming digital data into
binary ; storage units (bits, bytes, KBs, MBs and GBs) and OSes.
REMEMBER:You must revise units 1&2 before the exam next week!