Week 5: Algorithms and Programming Basics

**[WEEK 5: ALGORITHMS AND PROGRAMMING BASICS]** In this week's lecture, we will explore three main topics: 1. **Program Development, Flowcharts, and Algorithms** 2. **Programming Languages, Compilers, and Interpreters** 3. **Algorithms -- Pseudocode and Flowcharts** **[1. PROGRAM DEVELOPMENT...

**[WEEK 5: ALGORITHMS AND PROGRAMMING BASICS]** In this week's lecture, we will explore three main topics: 1. **Program Development, Flowcharts, and Algorithms** 2. **Programming Languages, Compilers, and Interpreters** 3. **Algorithms -- Pseudocode and Flowcharts** **[1. PROGRAM DEVELOPMENT, FLOWCHARTS, AND ALGORITHMS]** **What Is Program Development?** - **Definition:** Program development is the process of designing, writing, testing, and maintaining code that instructs computers to perform specific tasks. - **Phases of Development:** - **Planning:** Understand the problem and determine requirements. - **Design:** Outline the structure and flow of the program (using diagrams like flowcharts). - **Coding:** Write the actual code in a programming language. - **Testing:** Run the program to identify and fix errors. - **Maintenance:** Update the program as needed after deployment. **What Is an Algorithm?** - **Definition:** An algorithm is a step-by-step procedure or a set of rules to solve a problem or perform a computation. - **Example:** A recipe for baking a cake is like an algorithm---it lists the steps in order. - **Key Characteristics:** - **Input:** What you start with (data, parameters). - **Process:** The steps taken to transform the input. - **Output:** The final result. **Flowcharts: Visualizing Algorithms** - **Purpose:** Flowcharts are diagrams that visually represent the steps of an algorithm or process. - **Common Symbols:** - **Oval:** Start and End points. - **Rectangle:** Process or instruction. - **Diamond:** Decision (yes/no question). - **Parallelogram:** Input/Output operations. - **Arrows:** A line that connects & shows the relationship between the shapes. **Example Flowchart: Calculating the Sum of Two Numbers** flowchart TD A\[Start\] \--\> B\[Input Number 1 and Number 2\] B \--\> C\[Calculate Sum = Number1 + Number2\] C \--\> D\[Display Sum\] D \--\> E\[End\] *Diagram Explanation:* 1. **Start:** The process begins. 2. **Input:** The user is prompted to enter two numbers. 3. **Calculation:** The program computes the sum of the two numbers. 4. **Output:** The sum is displayed. 5. **End:** The process terminates. **Assignment 1** - **Task:** Create a flowchart for an algorithm that determines if a number is even or odd. - **Hints:** - Use a diamond symbol to represent the decision (i.e., checking if the remainder when divided by 2 equals 0). - Include input and output steps. **2. [PROGRAMMING LANGUAGES, COMPILERS, AND INTERPRETERS]** **Introduction to Programming Languages** - **Definition:** A programming language is a formal language comprising a set of instructions that produce various kinds of output. They are used to implement algorithms. - **High-Level vs. Low-Level:** - **High-Level Languages:** Closer to human language (e.g., Python, Java). Easier to read, write, and maintain. - **Low-Level Languages:** Closer to machine language (e.g., Assembly). Offers more control over hardware but is harder to read and write. **Compilers vs. Interpreters** - **Compilers:** - **Function:** Translate the entire source code into machine code before execution. - **Examples:** C, C++. - **Pros:** Faster execution since code is pre-compiled; optimizations can be applied. - **Cons:** Errors are reported after compiling the whole program, which can make debugging harder. - **Interpreters:** - **Function:** Translate and execute code line-by-line. - **Examples:** Python, JavaScript. - **Pros:** Easier to debug since execution stops at the error line; good for rapid prototyping. - **Cons:** Slower execution because translation happens during runtime. **Diagram: Compilation vs. Interpretation Process** flowchart LR subgraph Compilation A\[Source Code\] \--\> B\[Compiler\] B \--\> C\[Machine Code\] C \--\> D\[Execution\] end subgraph Interpretation E\[Source Code\] \--\> F\[Interpreter\] F \--\> G\[Direct Execution\] end *Diagram Explanation:* - **Compilation:** The compiler converts the complete source code into machine code which is then executed. - **Interpretation:** The interpreter reads and executes each line of code directly without a separate machine code stage. **Assignment 2** - **Task:** Write a brief paragraph (4--5 sentences) comparing compilers and interpreters. Focus on one advantage and one disadvantage of each. **3. Algorithms -- Pseudocode and Flowcharts** **What Is Pseudocode?** - **Definition:** Pseudocode is a plain language description of the steps in an algorithm. It is not written in any specific programming language syntax but in an easy-to-understand format. - **Purpose:** It helps programmers plan their code and logic before writing actual code. - **Key Features:** - Uses simple language. - Focuses on logic rather than syntax. - Helps in brainstorming and debugging. **Writing Effective Pseudocode** - **Guidelines:** - **Keep It Simple:** Use clear and concise language. - **Structure:** Break down the problem into smaller, manageable parts. - **Use Indentation:** Helps in showing hierarchy and decision structures (like loops and conditionals). **Example: Factorial of a Number** **Pseudocode:** START INPUT number SET factorial to 1 FOR each integer i from 1 to number DO SET factorial = factorial \* i END FOR OUTPUT factorial END **Flowchart for Factorial Calculation:** flowchart TD A\[Start\] \--\> B\[Input number\] B \--\> C\[Set factorial = 1\] C \--\> D\[Set i = 1\] D \--\> E{Is i \ F\[Set factorial = factorial \* i\] F \--\> G\[Increment i by 1\] G \--\> E E \-- No \--\> H\[Output factorial\] H \--\> I\[End\] *Diagram Explanation:* 1. **Start:** Begin the process. 2. **Input:** The user inputs a number. 3. **Initialization:** Factorial is set to 1, and a counter i starts at 1. 4. **Loop (Decision):** The algorithm checks if i is less than or equal to the number. 5. **Calculation:** Multiply the current factorial by i and increment i. 6. **Output:** Once the condition fails, output the factorial result. 7. **End:** Terminate the process. **Assignment 3** - **Task:** 1. Write pseudocode for finding the largest number in an array of integers. 2. Create a flowchart that represents the pseudocode you have written. - **Hints:** 1. Start by assuming the first element is the largest. 2. Loop through the array and update the largest number if a bigger number is found.