Software Development Basics PDF

Software development basics Slide 1 of 58  What is Programming? ▪ Programming is giving a set of instructions to a computer to execute. Slide 2 of 58  Programming vs Coding ▪ While sometimes used interchangeably, programming and coding...

Software development basics Slide 1 of 58  What is Programming? ▪ Programming is giving a set of instructions to a computer to execute. Slide 2 of 58  Programming vs Coding ▪ While sometimes used interchangeably, programming and coding actually have different definitions. ▪ Programming is the mental process of thinking up instructions to give to a machine (like a computer). ▪ Coding is the process of transforming those ideas into a written language that a computer can understand. Slide 3 of 58  Programming All Programs Have in Common: Take data and manipulate it to produce a result Input – Process – Output o Input: from files, the keyboard, or other input device o Process: perform some operations on the input to get the required result. o Output: display or print the result using the monitor, printer, or other output device. Slide 4 of 58  Programming languages ▪ Programming languages is a system of notation for writing computer programs. They are used to best communicate with computers. ▪ Programming languages are either text-based or graphical. ▪ Programming has evolved from punch cards with rows of numbers that a machine read, to drag-and-drop interfaces that increase programming speed. Slide 5 of 58  Punch cards Slide 6 of 58  Drag-and-drop interfaces Slide 7 of 58  Programming Languages Machine language “Natural language” of computer component Machine dependent Assembly language English-like abbreviations represent computer operations Translator programs convert to machine language High-level language Allows for writing more “English-like” instructions Contains commonly used mathematical operations Slide 8 of 58  Translators Compiler Converts high-level language programs to machine language Example: C, C++, C# Interpreter Execute high-level language programs without compilation Example: Perl, Python and Matlab Assembler Converts Assembly language programs to machine language Example: GAS Slide 9 of 58 How do we solve a problem using a computer? Problem Software Design: choose algorithms and data structures Algorithm Programming: use language to express design Program Compiling/Interpreting: convert language to Instruction machine instructions Set Slide 10 of 58 10  Problem Solving Problem Statement stated using "natural language" may be ambiguous, imprecise Algorithm step-by-step procedure, guaranteed to finish definiteness, effective computability, finiteness Program A program is a collection of instructions. express the algorithm using a computer language high-level language, low-level language Slide 11 of 58  Problem Solving ▪ A program solves a problem by: Taking in data Manipulating the data Producing some information ▪ If you can break a problem down into these steps, you can create a program to solve it. ▪ But do we start writing code as soon as we run into a problem? Answer: No ! Slide 12 of 58  Program Development Cycle ▪ When Developing a program in the real world, there are seven steps: 1) Analyze the problem 2) Plan a solution 3) Design an interface 4) Write the code 5) Test and debug 6) Document the program 7) Maintain the program Slide 13 of 58  Analyze the Problem ▪ Understand what the problem is and what the solution should be ▪ Keep in mind what the End User should be able to see and do. User – Anyone who uses the program. End User – The person whom the program was designed for him/her to use. ▪ Also keep in mind what the CORRECT solution to the problem is. ▪ This needs to be done before ANY of the following steps can take place. Slide 14 of 58  Algorithms vs. Programs ▪ An Algorithm is a step-by-step procedure devised for the purpose of taking in data and producing the correct output. ▪ A program is the actual implementation of an algorithm in a programming language. ▪ Before writing a program, you must develop an algorithm to solve a problem. ▪ It is highly recommended to think about the problem first, then develop an algorithm, then write the program. Slide 15 of 58  Plan a Solution ▪ Once you understand the problem, you can develop an algorithm. ▪ Create precise steps for the entire flow of the program. Usually in the form of: ▪ Get Input ▪ Validate Input ▪ Manipulate Input ▪ Output Solution ▪ Every detail should be covered in the algorithm. ▪ Consider what is logical and illogical for the control flow. ▪ There are many tools programmers use to model the flow of a program. Slide 16 of 58  Modeling Tools To help understand the steps of an algorithm, programmers use a variety of tools: ▪ Pseudocode is a description of an algorithm using everyday wording, but molded to appear similar to a simplified programming language. ▪ Flowchart is a type of diagram that represents a workflow or process. A flowchart can also be defined as a diagrammatic representation of an algorithm, a step-by-step approach to solving a task. Slide 17 of 58  Flowchart symbols ▪ Terminal: is an oval that indicates the beginning and end of a program. It usually contains the words Start or End. ▪ Flowline: is a line from one symbol pointing towards another to show the process’s order of operation. This displays the flow of execution in a program. Slide 18 of 58  Flowchart symbols ▪ Input/Output: input/output is represented by a rhomboid and indicates the input or output of data. This is similar to setting a value to a variable. ▪ Process: represented by a rectangle, is an operation that manipulates data. Slide 19 of 58  Flowchart symbols ▪ Decision: represented by a rhombus and show a conditional operation that will determine which path a program should take. This is similar to conditional statements which control the flow of execution in a program. ▪ Connector: Used to join flow lines. Slide 20 of 58  Three Basic Constructs Slide 21 of 58  Flowcharts for three constructs Slide 22 of 58  Three Basic Constructs ▪ There are three basic ways to decompose a task: Slide 23 of 58  Sequential ▪ Do Subtask 1 to completion, then do Subtask 2 to completion, etc Slide 24 of 58  Sequential ▪ Example 1: Write an algorithm and draw a flowchart to convert the length in feet to centimeter. ▪ Length in cm= length in feet * 30.48 Slide 25 of 58  Sequential ▪ Example 1: ▪ Pseudocode: Input the length in feet (Lft) Calculate the length in cm (Lcm) by multiplying LFT with 30.48 Print length in cm (LCM) ▪ Algorithm: Step 1: Input Lft Step 2: Lcm  Lft x 30.48 Step 3: Print Lcm Slide 26 of 58  Sequential ▪ Example 1: Start ▪ Flowchart: Input Lft Lcm  Lft x 30.48 Print Lcm End Slide 27 of 58  Sequential ▪ Example2: Write an algorithm and draw a flowchart that will read the two sides of a rectangle and calculate its area. ▪ Rectangle area = length * width Slide 28 of 58  Sequential ▪ Example 2: ▪ Pseudocode: Input the width (W) and Length (L) of a rectangle Calculate the area (A) by multiplying L with W Print A ▪ Algorithm: Step 1: Input W,L Step 2: A = L * W Step 3: Print A Slide 29 of 58  Sequential ▪ Example 2: Start ▪ Flowchart: Input W, L ALxW Print A End Slide 30 of 58  Sequential ▪ Example 3: Consider the problem of finding out how many stamps you need to put on an envelope to mail it. ▪ The rule here is that you need 1 stamp for every 5 sheets of paper in the envelope. ▪ So, the algorithm looks something like this: ▪ Get the number of sheets from the user. (Input) ▪ Divide the number of sheets by 5 (Process) ▪ Round the result from step 2 the highest whole number (Process) ▪ Output the number of stamps (Output) Slide 31 of 58  Sequential ▪ Example 3: ▪ So, a specific example looks like ▪ The user inputs 16 sheets of paper ▪ Dividing 16 by 5 results in 3.2 ▪ Rounding 3.2 up results in 4 ▪ Output 4 stamps Slide 32 of 58  Sequential ▪ Example 3: Start ▪ Flowchart: Read sheets Set stamps = sheets / 5 Round stamps up to next whole number Display: "You will need: " stamps Slide 33 of 58 End  Sequential ▪ Example 3: ▪ What could go wrong? ▪ What if the user inputs “Banana” sheets of paper? Slide 34 of 58  Conditional/ Decision ▪ If condition is true, do Subtask 1; else, do Subtask 2. Slide 35 of 58  Conditional/ Decision ▪ The expression A>B is a logical expression. ▪ it describes a condition we want to test. Yes No ▪ if A>B is true (if A is greater than B) we A>B take the action on left. ▪ print the value of A Print A Print B ▪ if A>B is false (if A is not greater than B) we take the action on right ▪ print the value of B Slide 36 of 58  If–then–else Structure ▪ The structure is as follows: If condition then true alternative else false alternative endif Slide 37 of 58  If–then–else Structure ▪ The algorithm for the flowchart is as follows: Yes No A>B If A>B then Print A Print A Print B else Print B endif Slide 38 of 58  Relational Operators Slide 39 of 58  Conditional/ Decision ▪ Example 3: Stamp problem (Revised Algorithm) ▪ Get the number of sheets from the user. (Input) ▪ Check to see if the input is a positive number. (Validate) ▪ Divide the number of sheets by 5 (Process) ▪ Round the result from step 2 the highest whole number (Process) ▪ Output the number of stamps (Output) Slide 40 of 58  Conditional/ Decision Start Read sheets Yes Is sheets No positive number? Set stamps = sheets / 5 Display error Round stamps up to next message whole number Display: "You will need: " stamps Slide 41 of 58 End  Conditional/ Decision ▪ Example 4: Create an algorithm and a flowchart that will read two numbers and then display the bigger number. Slide 42 of 58  Conditional/ Decision ▪ Example 4: ▪ Algorithm: 1. Input number1, number2 2. If (number1 > number2) then MAX = number1 Else MAX = number2 Endif 3. Print “The largest value is”, MAX Slide 43 of 58  Conditional/ Decision ▪ Example 4: Start ▪ Flowchart: Input number1, number2 Yes No number1>number2 MAX number1 MAX number2 Print “The largest value is”, MAX End Slide 44 of 58  Conditional/ Decision ▪ Example 5: Create an algorithm and a flowchart that will accept a student mark and then display “PASS” if the mark is 50 or more and display “FAIL” otherwise. Slide 45 of 58  Conditional/ Decision ▪ Example 5: ▪ Algorithm: 1. Input mark 2. If (mark >= 50) then Print “PASS” Else Print “FAIL” Endif Slide 46 of 58  Conditional/ Decision ▪ Example 5: Start ▪ Flowchart: Input mark Yes No mark >= 50 Print “PASS” Print “FAIL” End Slide 47 of 58  Repetition ▪ Do Subtask over and over, as long as the test condition is true. Slide 48 of 58  Repetition ▪ Example 6: Write an algorithm and draw a flowchart to find the sum of numbers from 1 to 10. ▪ 1+2+3+4+5+6+7+8+9+10 Slide 49 of 58  Repetition ▪ Example 6: ▪ Algorithm: Step 1: Set sum to 0, number to 1 Step 2: update sum as sum = sum + number Step 3: increment number Step 4: Repeat steps 2 and 3 until number = 10 Step 5: Print sum Slide 50 of 58  Repetition ▪ Example 6: Start ▪ Flowchart: Set sum = 0 Set number = 1 No number Equal == Slide 57 of 58  Logical operators Logical And Or Not Slide 58 of 58