Transcript Unit 7
M150 – DATA, COMPUTING and INFORMATION
q
Week 7
(Unit 6)
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M150 – DATA, COMPUTING and INFORMATION
What you should do this week?
Read Unit 6
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M150 – DATA, COMPUTING and INFORMATION
Outline
Unit 6
What’s next
Some review questions
Your questions
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Unit 6: Five Themes
Distinguishing: Computer as a system that is made up of
Software, Hardware and Firmware.
Describing: Functions of different components of a
computer ( memory, OS, mother board, etc….).
Collaborating: Different computer components to process a
computer program.
Understanding: How computer understand our
commands???!!!.
Introducing: The mechanism of how the software is going to
skip or repeat a sequence of instructions
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Unit 6: Agenda
Hardware, Software and Computer system
The resources of a computer , and how they are managed.
Running a program.
Types of programming languages.
The structure of computer programs.
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Unit 6: Hardware, Software and Computer system
Hardware vs. Software
Computer Hardware and Software components work together in order to execute
computer program
Hardware: describes the physical parts of computer that can be touched.
Software: describes the information or the programming the computer uses, you
can't touch it
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Unit 6: Firmware
a software program or set of instructions programmed on a
hardware device (usually in the ROM)
It provides the necessary instructions for how the device
communicates with the other computer hardware
can be thought of as "semi-permanent" since it remains the
same unless it is updated
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Unit 6: Example1
"I bought a 100-pack of empty DVD discs and tried to burn a
video to a few of them but it would not work".
I contacted my DVD drive manufacturer and they suggested
that I update the firmware on the DVD drive.
The updated Firmware had a new set of computer code for my
drive instructing how to write to the DVD I’m using
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Unit 6: Hardware Vs. Software
Although Hardware and Software are different in nature,
there are related.
A solution to a computer problem can be implemented using
either Hardware or Software.
Hardware uses several tangible electronic circuits.
Software uses instructions to use same circuits.
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Unit 6: Reflection 1
EX: 2.3
A book could be thought of as being made of paper and ink, or
it could be thought of as being a collection of words and
sentences.
Which view is analogous to Software and which to Hardware?
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Unit 6: Computer as a system
The tutor asked us to define computer, after a discussion the result was a
computer is a machine that Accepts input, Process Input then it gives a
result as an Output.
So every machine that Accepts input, Processes that input, and produces
Output is called a system
Perfect
Then my mother’s Washing machine is a system
Yes
Or
No
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Unit 6: Agenda
Hardware, Software and Computer system
The resources of a computer, and how they are managed.
Running a program.
Types of programming languages.
The structure of computer programs.
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Unit 6: Reflection 2
EX:3.1
In what form are the data and Instructions stored in a
computer?
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Unit 6: CPU – The Heart Of Computer
The Central Processing Unit: (CPU also called processor) is the part of the computer that
executes program instructions. It consists of two parts:
1.
The Arithmetic and Logic Unit (ALU) is where all calculations and logical operations
are performed.
a- Arithmetic operations involve addition, subtraction, multiplication, and division.
b- Logic operations basically consist of comparing or combining two values:
• All ALUs can compare >, <, and =.
• Some ALUs can also compare >=, <=, and <>.
• Comparisons can be combined using the logical operations NOT, AND and
OR. Truth tables are used to formally define these logical operations.
2.
The Control Unit (CU): The control unit interprets program instructions. The control
unit communicates with main memory and with input and output device controllers. The
control unit directs the ALU to execute program instructions.
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Unit 6: CPU – The Heart Of Computer
The CPU Registers : are high-speed storage locations
within the CPU, used for specific tasks:
Memory Data Register (MDR) is used to hold data that are being
transferred to or from primary storage.
Memory Address Register (MAR) indicates the location of the data to be
stored or retrieved from primary storage.
Instruction Register (IR) holds the instruction being executed.
Program Counter (PC) holds the primary storage address of the next
instruction to be executed.
The address held in the PC ,instruction cycle
insures sequential execution of instructions.
Jumps to another part of the program are achieved by instructions,
which reset the contents of the program counter.
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Unit 6: CPU – The Heart Of Computer
Accumulator (AC) holds the results of ALU operations.
Program Status Register (PS) contains binary flags that signal the results
of the previous operation.
For example the carry bit will be set to 1 if the last arithmetic operation
lost a carry bit, and to 0 otherwise. Other condition codes indicate
whether the last result was negative, zero or overflowed.
General-purpose registers are used for different purposes.
The first three registers are used by the control unit and are not
accessible to the programmer.
The arrangement of registers define the processor architecture.
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Unit 6: Memory
(also called primary storage, internal storage, or main memory).
Memory is the part of the computer that holds data for processing, programs, and
information waiting to be output to secondary storage.
There are three main characteristics of memories:
The capacity of the memory varies in different computers and is measured in bytes.
A byte consists of 8 binary digits called bits.
Each bit can represent binary 0 or binary 1. Each byte represents one character in
memory.
There are four commonly used units of memory capacity:
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Unit 6: Memory
There are two types of memory chips:
Random access memory (RAM): Data and programs must be loaded
from external storage (such as disk) into RAM before it can be used by
the processor. RAM is volatile (temporary).
Read only memory (ROM): chips have programs built into them at the
factory and cannot be changed by the user, thus they are not volatile.
programmable ROMs (PROM) that can be programmed by the user
using special devices to save his own information.
ROM typically contains special instructions to start up the computer,
give keyboard keys their special control capabilities and put
characters on the screen.
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Unit 6: Memory hierarchy
Memory hierarchy: there is a memory hierarchy consisting of
primary memory (CPU internal registers, cache memory,
main memory) and secondary memory (external devices
such as disks)
Cache memory: is a high-speed expensive RAM memory
used to store copies of the most frequently accessed
information in main memory.
Virtual memory: Virtual memory is a memory system used to
increase the effective size of the computers physical main
memory.
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Unit 6: Secondary (external) storage
We mentioned before that the main memory is volatile (temporary).
If the power is turned off program and data disappear.
External storage is nonvolatile (permanent).
External storage also has much more capacity than the primary memory.
There are two approaches to external storage:
sequential access and
direct access.
The most widely used external storage media are
-floppy disks,
-hard disks,
-optical disks and
-magnetic tapes.
Disks are direct access storage media, while tapes are sequential access
storage media.
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Unit 6: Operating System
Is the most important system software component.
It interacts between the application software and the computer and
manages the computer’s internal resources.
Within the OS, besides the kernel, there is a group of other programs
called utility programs, that perform common tasks, such as formatting
disks, copy files from other disks, backup disks, remove and rename
files, and others.
Mainframes and minicomputers have powerful OS, including virtual
memory, multiprogramming and multiprocessing, where many users can
run different programs at the same time. Microcomputer OS focus on a
single user.
The most important operating systems are: DOS, Microsoft Windows,
Unix, Linux and MAC.
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Unit 6: Operating System
The Operating system has the following functions;
Provision of user interface
Management of the memory
Coordination and control of peripheral devices.
Scheduling access for the processor
Interface between Hardware and computer applications.
Provide basic utilities (disk formatting, file management,
etc….).
The bootstrap loader: is a program that is stored permanently in
the computer’s electronic circuitry in ROM. This process is
called booting.
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M150 – DATA, COMPUTING and INFORMATION
Unit 6: Agenda
Hardware, Software and Computer system
The resources of a computer , and how they are managed.
Running a program.
Types of programming languages.
The structure of computer programs.
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Unit 6: The Fetch/execute cycle
During the program execution the CPU do the following steps:
Get an instruction from the program.
Find and transfer any data necessary to perform instruction.
Carry out the instruction.
The process of locating, transferring and carrying out a single
instruction during execution is called fetch/execute cycle.
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Unit 6: Continue
During each cycle the CPU must:
Locate the next instruction in the program which is stored in the main
memory (first one is used if the execution has just started).
Transfer the instruction in to the processor by putting it in a register.
Decode the instruction.
Locate any data located in the main memory which refers to the
instruction.
Do the processing.
Place the result in an appropriate register.
If needed move result back to the main memory to be used later.
Increment the program counter by 1.
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Unit 6: Example executing Program
Executing Program
Instruction
LDA
501
ADD 502
STO 503
HLT 000
Memory
location of
instructions
701
702
703
704
Data
Memory
location of data
2
3
?
501
502
503
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Unit 6:Continue
operator
operand
LDA 501
address of
a memory
location
LoaD
Accumulator
part of the
computer's memory
The Accumulator
Before LDA
executes
after LDA
executes
???
?
2
3
?
500
501
502
503
2
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Unit 6:Continue
operator
operand
ADD 502
address of
a memory
location
ADD to
Accumulator
The Accumulator
before ADD
executes
after ADD
executes
2
part of the
computer's memory
?
2
3
?
500
501
502
503
5
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Unit 6:Continue
operator
operand
STO 503
STOre
Accumulator in
memory
The Accumulator
before STO
executes
after STO
executes
address of
a memory
location
computer's memory
before STO
?
2
3
?
500
501
502
503
computer's memory
after STO
5
5
?
2
3
5
500
501
502
503
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Unit 6:Continue
operator
operand
HLT 000
HaLT
dummy
value - not
used
No effect on accumulator or memory
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Unit 6: Agenda
Hardware, Software and Computer system
The resources of a computer , and how they are managed.
Running a program.
Types of programming languages.
The structure of computer programs.
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Unit 6: Types of programming languages.
Five Generations of Programming Languages
GENERATION
First
Second
Third
Fourth
Fifth
NAME
Machine
Assembly
Procedural and structural
Object oriented
Natural
SAMPLE STATEMENT
10010001
ADD A, B JMP L
Overtime:= 5 0;
FIND NAME "JONES“
IF patient is dizzy, THEN check
temperature and blood pressure
Computer professionals talk about levels or generations of programming
languages, ranging from ‘low’ to ‘high.’ Programming languages are called lower
level when they are closer to the language the computer itself uses.
The computer understands the 0s and 1s that make up bits and bytes.
Programming languages are called higher level when they are closer to the
language humans use that is, for English speakers, more like English.
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Unit 6: Machine Languages: The First Generation
We mentioned earlier that a byte is made up of bits,
consisting of 1s and 0s.
These 1s and 0s may correspond to electricity’s being on or
off in the computer.
They may also correspond to a magnetic charge’s being
present or absent on storage media such as disk or tape.
Data represented in 1s and 0s is said to be written in
machine language.
To see how hard this is to understand, imagine if you had to
code this :
111100100111001111010010000100000111000000101011
Machine languages also vary according to computer design another characteristic that makes them hard to work with
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Unit 6: Assembly Languages: The Second Generation
Assembly languages have a clear advantage over the 1s and 0s of machine
language because they use abbreviations or mnemonics.
These are easier for human beings to remember.
The machine language code we gave earlier could be expressed in
assembly language as:
ADD A, B
JMP L
Assembly language is also considered low-level.
Assembly languages also vary from computer to computer.
With the third generation, we advance to high-level languages, many of
which are considered portable languages.
That is, they can be run on more than one kind of computer—they are
“portable” from one machine to another.
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Unit 6: High-Level Procedural Languages: The Third Generation
People are able to understand languages that are more
like their own (e.g., English) than machine languages or assembly
languages. These more English-like programming languages are called
“high-level” languages.
However, most people still require some training in order to use higherlevel languages. This is particularly true of procedural languages.
Procedural languages are programming languages with names like
BASIC, Pascal, C, COBOL, and FORTRAN.
They are called “procedural” because they are designed to express the
logic—the procedures—that can solve general problems.
For a procedural language to work on a computer, it must be translated
into machine language Depending on the language, this translation is
performed by either a compiler or an interpreter.
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Unit 6: High-Level Procedural Languages: The Third Generation
A compiler converts the programmer’s procedural language program,
called the source code; into a machine language code, called the object
code.
An interpreter converts the procedural language one statement at a time
into machine code just before it is to be executed. No object code is
saved.
What is the difference between using a compiler and using an interpreter?
When a program is run, the compiler requires two steps. The first step is
to convert the entire program’s source code to object code.
The second step is to run the object code. The interpreter, in contrast,
converts and runs the program one line at a time.
The advantage of a compiler language is that once the object code has
been obtained, the program executes faster.
The advantage of an interpreter language is that programs are easier to
develop.
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Unit 5: Problem-Oriented Languages: The Fourth Generation
Third-generation languages are valuable, but they require
training in programming.
Object-oriented languages, also known as very high-level
languages, require little special training on the part of the
user.
Unlike general-purpose languages, object-oriented
languages are designed to solve specific problems. Some of
these fourth-generation languages are used for very specific
applications. Many consider Lotus 1-2-3 and dBASE to be
flexible fourth-generation languages.
Query languages: Query languages enable nonprogrammers
to use certain easily understood commands to search and
generate reports from a database. An example is the
commands used on an airline reservations system
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Unit 6: Natural Languages: The Fifth Generation
Natural languages are still being developed.
They are designed to give people a more human (“natural”)
connection with computers.
The languages are human languages: English, French,
Japanese, or whatever.
Researchers also hope that natural languages will enable a
computer to learn — to “remember” information, as people
do, and to improve upon it.
Clearly this area is extremely challenging.
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Unit 6: Agenda
Hardware, Software and Computer system
The resources of a computer , and how they are managed.
Running a program.
Types of programming languages.
The structure of computer programs.
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Unit 6: The basic building blocks of computer programs
All programs can be built from three logical building blocks
• Selection/ifs
• If the traffic in the high
street is heavy
• take the first left
• take the first right
Sequence
• Take the first left
• Take the second right
• Take the third exit at
the roundabout
• take the first left
• else
• follow the high
street to the end
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Repetition/loops
• while you have not yet
reached the turnoff for
Little Whamping
• go straight ahead at
each roundabout
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Unit 6:Continue
Let's not worry about the programming language for a while
The syntax for how you do sequence, selection and
repetition varies from programming language to
programming language but the basic structures stay the
same.
Once you have the concepts clear you can apply them to any
language (JavaScript, Java, Visual Basic, C#, C++, Perl etc
etc)
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Unit 6: Sequence
The only thing to worry about is getting the instructions in the correct
order
post the
envelope
buy a birthday
card
buy a stamp
put the card in
the envelope
address the
envelope
write in the
birthday card
Put these instructions into a logical sequence for
Robbie the willing but slightly dim robot!
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Unit 6: Selection
A selection instruction allows you to write programs (and remember
programs are basically just plans) that will operate in different ways
depending on circumstances
If I win the lottery this
Saturday I'll tell my boss
what I think of her on
Monday otherwise I'll start
an OU degree and get a
better job in a couple of
years
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Unit 6: True or false
Selection always includes a condition that can be
evaluated when the program runs (i.e. the plan is
executed) to be true or false (this is called a Boolean
expression).
The truth or falsity of the condition determines which
path is taken.
a "flow chart"
The condition is
like a fork in the
road determining
which path you
take
I win the
lottery this
Saturday
True
tell my boss what I
think of her on
Monday
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False
start an OU degree
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Unit 6: Selection exercises
If Charlton Athletic stay in the premiership next season I'll
renew my season ticket. Otherwise I'll spend my money on
getting Sky instead.
Identify the condition and draw a flow chart diagram
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Unit 6: Repetition
A repetition instruction allows one or more instructions to be
repeated a number of times.
While I've got a chance of
winning I'll keep putting one
foot in front of the other
I've got a
chance of
winning
False
True
Sorry Paula!
put one foot in
front of the other
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Unit 6: Repetition exercise
I'm getting Robbie to plant tulip bulbs in the garden.
I've given him a bag of bulbs and told him that
while there are still any left in the bag he should
take one out, dig a hole for it and put it in.
Draw a flow chart representing my instructions to
Robbie.
What's wrong with these instructions for Robbie
To make cups of tea for the family repeat the
following actions:
put milk in cup
put teabag in cup
pour in boiling water
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Unit 6: Conditions again
Important observation: both selection and repetition
are controlled by conditions that can be evaluated
to true or false (i.e. Boolean expressions).
Selection - which path should I follow?
Repetition - how often should I go round the loop?
Because Boolean expressions are of crucial
importance a considerable chunk of Unit 6 section 6
is devoted to them.
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Unit 6: Compound conditions
Often we want to combine separate conditions when using
them to control a selection or a repetition e.g.
if (the customer is over 64
or the customer is under 18)
charge them reduced rate
else
charge them full rate
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Unit 6: Evaluating compound conditions
You have to evaluate the separate parts and combine them
according to rules in order to evaluate the truth or falsity of the
overall expression
true/false
true/false
true/false
(the customer is over 64 or the customer is under 18)
The rules used to combine the separate parts depend on the
operator used. In this case the operator is or.
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Unit 6: Evaluating or expressions
If either or both of the sub-expressions are true then
the whole expression evaluates as true. Only if both
the sub-expressions are false does the whole
expression evaluate to false.
Evaluate
(the customer is over 64 or the customer is under 18)
When
a)
b)
c)
the customer is 17
the customer is 65
the customer is 63
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Unit 6: Another or exercise
if (the patient is over 12 or the patient is under 60)
prescribe the adult dosage
else
prescribe reduced dosage
What will happen when the patient is:
a) 16
b) 11
c) 70
Is there a problem here?
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Unit 6: Evaluating and expressions
If (the sky is purple and there is a shower of dead
frogs)
stay under the duvet
else
get up and go to work
If either or both of the sub-expressions are false
then the whole expression evaluates as false. Only
if both the sub-expressions are true does the whole
expression evaluate to true.
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Unit 6: An and exercise
If (the date is an odd number and there's an "r" in the
month)
drink Coffee
else
drink Tea
What's to be drunk on:
a)
May 11th
b)
March 21st
c)
September 22nd
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Unit 6: Mixing it exercise
If ((gender = "male" and age > 64)
or
(gender = "female" and age > 59))
charge reduced rate
else
charge full rate
What will happen for:
a)
b)
c)
a male of 63
a female of 60
a male of 25
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Unit 6: Mixing it exercise 2
if (monthly income > 2000
or (monthly income > 1000 and
monthly outgoings < 500))
grant credit
else
refuse credit
What will happen for:
a)
b)
c)
someone with monthly outgoings of 1800 and a monthly
income of 2100
someone with a monthly income of 900 and monthly
outgoings of 200
someone with a monthly income of 1200 and monthly
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outgoings of 600
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What’s next
Unit 7: An introduction to programming using JavaScript
Introduction
Getting started
Programming for selection: the if statement
Programming for repetition: the while statement
Programming for repetition: the for statement
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Some review questions
What is assembly language?
Write using assembly language a program that adds 2
numbers. Using your program describe what is meant by
operator and operand .Also describe what happens to in the
computer hardware as the program is executed? In this case
you can assume that the first number is stored at memory
location 400 is 3 and the second number is stored at 401 is 4.
Also assume that the starting memory location is 700.
Define virtual and cache memory?
Describe using an example the meaning of low and high level
language?
What is meant by compiler and interpreter?
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Your questions
?
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