BIM111 Introduction to Computer Engineering

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BIM111 Introduction to Computer Engineering

• Software

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Contents

• Software, Program, Algorithm
• Basic Operation of the Computer
• System Software Components
• High level languages, Compiler, Assembler,
  Linker, Loader and Operating system
• Software Development Cycle

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Program (Software)

• Conceptually a program is a step-by-step solution
  to a problem
• Also named an algorithm
• A well-defined computational procedure that takes
  some values (data) as input and produces some
  results as output

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Example Program Compute the sum, product and avg
of 2 numbers, a b
DATA
ALGORITHM
a ? 10 b ? 40 sum ? ab product ? ab avg ?
sum/2 print sum print product print avg
a
10
?
?
b
?
40
sum
?
50
product
?
400
avg
25
?
SCREEN
50 400 25
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Basic Operation of the Computer

• loop
• Fetch the next instruction from memory
• Decode the instruction
• Interpret what the instruction means
• Fetch the operands (if necessary)
• Fetch the operands from memory to CPU registers
• Execute the instruction
• Perform what the instruction is telling us to do
  (add, subtract, multiply, divide, )
• Store the result back to memory (if necessary)
• repeat

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Example Program Execution
MEMORY
S1 a ? 10 S2 b ? 40 S3 sum ? a b S4 product
? ab S5 avg ? sum/2 S6 print sum S7 print
product S8 print avg
Instructions
CPU
Registers
IP
ALU/ FPU
10
10
50
SCREEN
a
10
?
S2
S4
S5
S6
S7
S8
S1
S3
40
40
25
50 400 25
b
Control Unit
40
?
50
400
sum
?
50
DATA
product
?
400
avg
?
25
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From Algorithm to 0s and 1s

• Although we showed the instructions stored in
  memory in pseudo-code (human readable form), what
  is really stored is 0s and 1s
• Remember a computer only understands 0s and 1s
• This means that we need tools that would help us
  convert the program from human-readable form to
  the machine-readable form called the machine
  language
• These tools are called system software tools

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System Software Components

• We have several system software components to
  make programming the computer easy
• High-level Programming Languages (C, C, Java,
  C, ..)
• Compiler
• Converts your programs implemented in high-level
  language to assembly language, which are mnemonic
  codes that correspond one-to-one with machine
  language
• Assembler
• Converts programs implemented in assembly
  language to machine language, which are binary
  number codes understood by a specific CPU
• Linker
• Combines several object files together into an
  executable
• Loader Operating System
• Loads your program into memory for execution
• Relevant Course BIM201 System Software

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Operating System

• Is a layer of software that exports an
  easy-to-use interface to program the hardware

User Programs
P1
P2
Pn
System call API
Operating System (Windows, Linux, Solaris, )
Hardware API
Hardware

• User programs make use of the hardware through
  the services provided by the OS
• Thus OS makes life easier for user programs
• Relevant course BIM322 Operating Systems

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Problem Solving

• Computer programs are written to solve problems.
• Coding a computer program should not be started
  until all plans are made.
• First, a solution is created, and then the
  program is coded in a computer language.
• The key is planning.

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Software Development Cycle

• 1. Specify problem requirements
• State the problem clearly understand what is
  required
• 2. Analyze the problem
• Identify the inputs (data), outputs (results),
  and any additional requirements
• 3. Design a solution (algorithm)
• Develop the list of steps that solves the problem
• Do Procedural Design or Object-Oriented Design
• 4. Implement the algorithm
• Code the algorithm using a programming language
  (C, C, Java, C, )
• Notice that an algorithm is independent of the PL

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Software Development Cycle (cont)

• 5. Test and verify
• Run the code with many sets of test data to
  verify that it does what it is supposed to do
• 6. Maintain and update code
• Modify the code as needed
• Relevant Courses
• Introduction to Computer Engineering
• C Programming
• Visual Programming
• Object Oriented Programming
• Advanced Programming Techniques
• System Analysis Design
• Software Engineering
• Programming Language Concepts

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Algorithms

• We use algorithms every day.
• Whenever we are doing a task, such as following a
  recipe or assembling a bookcase, the algorithm
  tells us each step in the proper order.

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Ex-ATM Machine

• Problem Design an algorithm for a simple ATM
  machine
• Get the password from the user
• If the password is not valid, construct an error
  message and skip to step 6.
• Get the inputs
• 3.1 Get the transaction type (deposit or
  withdrawal), and the amount from the user.
• 3.1 Get the current balance from the bank.
• (continued on next page)

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Ex-ATM Machine (cont)

• If the transaction type is deposit, add the
  amount to the current balance.
• If the transaction type is withdrawal, check the
  current balance
• 5.1 If amount is greater than the current
  balance, construct an error message and skip to
  step 6.
• 5.2 If amount is equal to or less than the
  current balance, subtract the amount from the
  current balance.
• Output the error message or the cash, and the
  current balance.
• Ask the user whether to repeat steps 3 through 6
  for another transaction.

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Ex1-Making a Sandwich

• Problem Design an algorithm to make peanut
  butter and jelly sandwich
• Inputs
• Bread (at least 2 slices)
• Peanut Butter
• Jelly
• Knife
• Plate to place the sandwich on
• Output
• One sandwich

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Ex1-Making a Sandwich (cont)

• Put the bread, peanut butter, jelly, knife and
  plate onto the workplace
• Place two slices of bread on the plate
• Using knife spread the peanut butter on one slice
• Spread jelly on the other slice using the knife
• Slap the two pieces together, sticky side in
• Eat the sandwich

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Ex1-Making a Sandwich (cont)

• Step 1 is the input
• Steps 2-5 explain the process
• Step 6 is the output
• Clearly, we must do steps one after the other
• We should not do step 5 before step 3 or the
  sandwich would not be very interesting

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Ex2-Convert Fahrenheit-to-Celsius

• Problem Design an algorithm to convert a
  fahrenheit temperature to celsius temperature
• Input
• Temperature in fahrenheit degrees
• Output
• Temperature in celsius degrees

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Ex2-Convert Fahrenheit-to-Celsius

• Prompt the user and get the fahrenheit
  temperature to convert
• celsius (fahrenheit-32)/1.8
• Print the fahrenheit and celsius degrees on the
  screen

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Ex3-Compute the sum, product and average of 2
numbers

• Problem Design an algorithm to find the sum,
  product and average of 2 numbers
• Input
• 2 numbers
• Output
• Sum, product and average of the numbers

sum
num1
program
prod
num2
avg
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Ex3-Compute the sum, product and average of 2
numbers

• Prompt the user and get number1 and number2
• sum number1 number2
• product number1 number2
• average sum / 2
• Print sum, product, average

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Ex4-Compute the circumference and the area of a
circle

• Problem Design an algorithm to compute the
  circumference and the area of a circle
• Input
• The radius of the circle
• Output
• The circumference and the area of the circle

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Ex4-Compute the circumference and the area of a
circle

• Prompt the user and get the radius of the circle
• circumference 2 3.14 radius
• area 3.14 radius radius
• Print the circumference and the area

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Ex5-Compute the minimum and maximum of 2 numbers

• Problem Design an algorithm to find the minimum
  and maximum of 2 numbers
• Input
• 2 numbers
• Output
• Minimum and maximum of the numbers

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Ex5-Compute the minimum and maximum of 2 numbers

• Prompt the user and get number1 and number2
• if (number1 lt number2)
• 2.1. min number1
• 2.2. max number2
• else (i.e., number1 gt number2)
• 3.1. min number2
• 3.2. max number1
• Print min and max

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Ex6-Compute the minimum of 3 numbers

• Problem Design an algorithm to find the minimum
  of 3 numbers
• Input
• 3 numbers
• Output
• Minimum of the numbers

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Ex6-Compute the minimum of 3 numbers

• Prompt the user and get number1, number2 and
  number3
• if (number1 lt number2)
• 2.1. if (number1 lt number3) then min number1
• 2.2. else (i.e., number3 lt number1) min
  number3
• else (i.e., number1 gt number2)
• 3.1. if (number2 lt number3) min number2
• 3.2. else (i.e., number3 lt number2) min
  number3
• Print min

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Ex7-Compute the minimum of 3 numbers (2nd
Algorithm)

• Prompt the user and get number1, number2 and
  number3
• min number1 (Assume that number1 is min)
• if (number2 lt min) min number2
• if (number3 lt min) min number3
• Print min