Lecture Notes: CS50 Week 1 - Introduction to C

Overview

• Instructor: David Malan
• Topic: Introduction to the C programming language
• Objective: Build upon fundamentals from Scratch (Week 0) with a focus on solving problems using C, a more traditional programming language.

Key Concepts

Transition from Scratch to C

• Scratch: Block-based visual programming suitable for young learners.
• C: Text-based, traditional programming language.
• Both Scratch and C involve functions, loops, and conditionals, but C requires more syntax and manual coding.

Basic C Programming

• Source Code: Code written by humans, needs to be converted to Machine Code (binary) for computers to execute.
• Compiler: A program that translates source code to machine code (e.g., Make in C).
• VS Code: A cloud-based coding environment used in CS50 for C programming.

Syntax Basics

• printf: Equivalent to Scratch's say. Used for output; requires format specifiers like %s for strings and %i for integers.
• #include <stdio.h>: Includes standard input/output library for functions like printf.
• Conditionals: if, else if, else structures for decision-making.
• Loops: while and for loops for repetition. do while for post-tested loops.
• Functions: Can define custom functions in C using void or return types (e.g., int).

Common Challenges

Errors and Bugs

• Missing Semicolons: Common mistake in C syntax.
• Type Errors: Mismatches between expected and actual data types.
• Scope Issues: Variables only exist within their declared scope.

Correctness vs. Design

• Efficiency: Use of else if statements to avoid unnecessary checks.
• Code Duplication: Avoid repetitive code by using loops and functions.

Programming Concepts Illustrated

Variables and Data Types

• Integers (int) and Strings: Basic data types in C.
• Characters (char): Single character data type.
• Floats and Doubles: For decimal numbers, with a focus on precision (floating-point arithmetic).

Practical Examples

• Mario Example: Creating a grid of blocks using nested loops.
• Hello, World!: Basic C program to print text to the console.
• Agree Program: Simple program to check user input using conditionals.

Advanced Topics

• Integer Overflow: Exceeding the storage capacity of a data type.
• Floating Point Imprecision: Limitations in representing decimals with a finite number of bits.
• Real-world implications: Historical bugs and design flaws (e.g., Y2K, Boeing 787 issue).

Tools and Commands

Command-Line Interface (CLI)

• Basic Commands: ls, mv, rm, cd for file navigation and manipulation.
• Make: Used to compile C programs.

VS Code

• Environment: Cloud-based setup for coding in C, with access to necessary libraries and tools.

Learning Outcomes

• Transitioning from visual to text-based programming.
• Understanding basic C syntax and structure.
• Identifying and solving common programming errors.
• Applying logical structures to solve problems efficiently.