Programing Fundamental

transcript

C Programming - Lecture 1 1

Programming FundamentalsCS-215/203

Engr. Qazi Shahzad AliLecture # 1

C Programming language

• Developed in 1972 by Dennis Ritchie at AT & T Bell Labs (American Telephone & Telegraph Company)

• Very widely used general purpose programming language

• Available on many machines and operating systems

• Design to be flexible and powerful

• Originally a replacement for assembly language (middle-level)

• C requires extreme care in programming

• C++ is a superset of C

Outline and Objective

1-Program Development Cycle

2-Programming Tools

1-Program Development Cycle

• Software refers to a collection of instructions for the computer

• The computer only knows what to do what the programmer tells it to do

• Therefore, the programmer has to know how to solve problems

Performing a Task on the Computer:

Input Processing Output

Program Planning

• A recipe is a good example of a plan

• Ingredients and amounts are determined by what you want to bake

• Ingredients are input

• The way you combine them is the processing

• What is baked is the output

1-Program Development Cycle:

1. Analyze Requirement: Define the problem, review the requirements.

2. Design Solution: Plan the solution to the problem (Solution algorithm or Program Logic)

3. Validate Design: Check Program design for accuracy.

1-Program Development Cycle:

4. Implement Design (Code): Translate the algorithm into a programming language (here, C).

5. Test Solution (Test and Debug): Locate and remove any errors in the program.

6. Complete the Documentation: Organize all the materials that describe the program.

2-Programming Tools:

1. Algorithms

2. Pseudo code

3. Flowchart

4. Hierarchy Chart (Structure chart)

1-Algorithm

• Step by step method of performing any task is called as Algorithm.

• Breaking up a big task in to smaller steps to make it easy to perform.

• Brushing teeth, making tea, getting ready for school/office are examples of some sort of algorithms

• Each step of the algorithm is called as Instruction

1-Algorithm

• A step by step series of instructions for solving a problem (a recipe is an example of an algorithm)

• Algorithms are key to solving many problems efficiently

1-Algorithm

• Example of making tea :

Begin1. Boil water

2. Put tea powder in the kettle

3. Pour boiled water in the kettle

4. Wait for three minutes

5. Boil milk

6. Put boiled milk in a cup

7. Add sugar to the cup

8. Empty the kettle in the cup

9. Stir the cup with a spoon

Algorithm Example

Unfortunately not every problem or task has a "good" Algorithmic solution.

• Unsolvable problems - no algorithm can exist to solve the problem (Halting Problem)

• "hard" (intractable) problems - algorithm takes too long to solve the problem (Traveling Salesman Problem)

• Problems with no known algorithmic solution

2-Pseudo code

2-Pseudocode?

• A program design technique that uses English words.

• Has no formal syntactical rules.• The idea is to represent the algorithm in a

form that is in between pure English and actual Running code

• Actually it’s one of the way for expression of Algorithm.

What is Pseudo code?

• Pseudo means “pretended” / “not real”

• Code refers to a computer programming language

• It is a written statement of an algorithm using a restricted and well-defined vocabulary

Pseudo code - format

• Write only one statement per line

• Capitalize initial keyword

• Indent to show hierarchy

• End multi-line structures

• Keep statements language independent

Pseudocode - format

• It should not be paragraphs or free-flowing sentences.

• It also should not contain any language-specific syntax.

• it should reflect what’s in your final program, not the ideas you scrapped along the way

Pseudo code Vocabulary

1.1. Input/outputInput/output

2.2. IterationIteration

3.3. Selection/DecisionSelection/Decision

4.4. ProcessingProcessing

1-Input/output

• 1- Input– INPUT, READ

– Used to get values from a data source, for example from a keyboard

– INPUT age

• 2- Output– DISPLAY, PRINT, WRITE

– Used to output values to a data sink, a screen or printer

– DISPLAY new_value

2-Iteration or Loop

• FOR <var> = <start value> to <stop value>

statement(s)

ENDFOR

• FOR count = 1 to 10

DISPLAY count

ENDFOR

3-Decision

• IF <condition> THEN statement

END-IF

• IF <condition> THEN statement

ELSE statement

END-IF

4-Processing

• ADD– ADD 3 TO count

• SUBTRACT– SUBTRACT 5 FROM count

• COMPUTE– COMPUTE 10 + count GIVING result

• SET– SET count TO 12

Example

Original Program SpecificationWrite a program that obtains two numbers from the user. It will print out the sum of those numbers.

Pseudo codeDISPLAY the message to enter the first integerREAD user’s first integer inputDISPLAY the message to enter the second integerREAD user’s second integer inputCOMPUTE first integer + second integer GIVING sumDISPLAY an output message that explains the answer as the sumDISPLAY the sum

Exercise

• Write Pseudocode to calculate the area of a circle

• Write Pseudocode to calculate sum of first ten numbers

• Write Pseudocode to calculate sum of first ten even numbers

Program Algorithm (stage 4) (pseudocode)

• Set count and sum to 0• DO WHILE there is more data

Get next number: valueIncrement countadd value to sum

LOOP• IF count > 0 THEN

Set average to sum/countDisplay average

ELSEDisplay ‘No data!’

END IF

Examples of Pseudocode:

• Fahrenheit to Celsius :1. get a value for f-temp 2. set the value of c-temp to (5 / 9) * (f-temp - 32) 3. return the value of c-temp

• Math:1. get a value for X, Y 2. if X <= Y then

1. return the value of X

3. else 1. return the value of Y

3-Flow Chart

• Logic diagram to describe each step that the program must perform to arrive at the solution.

• A popular logic tool used for showing an algorithm in graphics form.

Flowchart Symbol

• Programmer prepares flowchart before coding.

• Most common flowchart symbols are:

Flow line Terminal Input/Ouput Decision Processing

Purpose of Flowcharting:

• An aid in developing the logic of a program.

• Verification that all possible conditions have been considered in a program.

• Provides means of communication with others about the program.

• A guide in coding the program.

• Documentation for the program.

Flow Chart (using Boxes) Example of making tea:

Boil water

Put tea powder in kettle

Pour boiled water in kettle

Empty kettle in cup

Wait for three minutes

Put boiled milk in cup

Stir the cup with a spoon

Add sugar to the cup

Boil milkEnd

Example of Flowchart: Ordering a Burger

Algorithm 1 (Standard Process):1. Approach Counter2. Order Burger3. If You Want Fries Then

1. Order Fries4. Else, Go To Next Step5. If You Want Drink Then

1. Order Drink 6. Else, Go To Next Step7. Pay cashier

Algorithm 2 (Improved Process):1. Approach counter2. Order Combo Meal3. Pay cashier

Pseudocode

Want Fries

Cold Drink

Approach Counter

Pay Cashier

Flowchart

Order Burger

Order Fries

Order drinks

Example of Flowchart and Pseudocode:

Computing The Sum, Average, and Product of Three Numbers

Read X, Y, Z

S = X + Y + ZA = S / 3P = X x Y x Z

Write S, A, P

Flowchart

1. READ X, Y, Z2. COMPUTE SUM (S) As X + Y + Z3. COMPUTE Average (A) As S / 34. COMPUTE Product (P) As X x Y x Z5. WRITE (Display) the Sum, Average,

and Product

Pseudocode

1. READ A, B2. IF A is less than B

1. BIG = B2. SMALL = A

3. ELSE1. BIG = A2. SMALL = B

4. Write (Display) BIG, SMALL

Pseudocode

Determine Large/Small

1. READ A, B2. IF A is less than B

1. BIG = B2. SMALL = A

3. ELSE1. BIG = A2. SMALL = B

4. Write (Display) BIG, SMALL

PseudocodeStart

Read A, B

BIG = ASMALL = B

Write BIG, SMALL

A < B?

NoBIG = BSMALL = A

Flowchart

Example of Flowchart and Pseudocode: Computing Interest on a Loan

READ NameBalance, Rate

COMPUTE Interest = Balance X Rate

WRITE Name,Interest

1. READ Name, Balance, Rate2. COMPUTE Interest as

balance x Rate3. WRITE (DISPLAY) Name And Interest

Pseudocode

Flowchart

4-Hierarchy Chart

4-Hierarchy Chart?

• Shows the overall program’s structure.

• Describes what each part, or Module, of the program does.

• Also how each module relates to other modules in the program.

• Main benefit: Provide help in the initial planning of a program.

Example of Hierarchy Chart

Making of Tea

1-Boil Water 2-Boil Milk 3-Mix A & B

Add Tea Powder

Add Sugar“A”Wait for 3 Minutes

“B”Mix Sugar +

Boil Milk

Tea is Ready

Class ProblemProblem: calculate and report the

grade-point average for a class

General Steps

• Problem: calculate and report the grade-point average for a class

• Discussion: the average grade equals the sum of all grades divided by the number of students

• Output: Average grade• Input: Student grades• Processing: Find the sum of the grades; count the

number of students; calculate average

Flowchart: Determine the Average Grade

Ex: Three grades: 50, 75, 100Startcounter = 0; sum = 0Get grade 50counter = 1; sum = 50Get grade 75counter = 2; sum = 125Get grade 100counter = 3; sum = 225No more dataAverage = 225 / 3 = 75Display 75End

Pseudocode:Determine the Average Grade

• Determine the average grade of a class: Start

SET counter to zeroSET sum to zeroIF there are more data (grades)– READ the next grade– INCREMENT the counter by 1– ADD the grade to the sumELSE– COMPUTE average = sum / counterDISPLAY averageEnd

Another Example of Hierarchy Chart:

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