CS50 Week 1 Lecture Notes

Introduction

• Week 1 builds upon concepts from Week 0.
• Transition from Scratch to C programming language.
• Core programming concepts such as functions, conditionals, loops, and variables from Scratch are now translated into C.
• Programming involves converting source code to machine code (0s and 1s).
• Compilers are tools that translate source code to machine code.

Programming Environment

• Use of VS Code in a cloud-based environment (cs50.dev) with a GitHub account.
• VS Code features: file explorer, code editor, and terminal window.
• Introduction to command line interface (CLI).
• Importance of terminal commands like ls, cd, mkdir, mv, rm.

Writing C Programs

• Hello World in C:
  • Syntax: printf("Hello, world\n");
  • Requires #include <stdio.h> for input/output functions.
  • Functions: printf as equivalent to Scratch's say.
  • Escape Sequences: new line \n, quote \", backslash \\.

User Input and Variables

• Use of CS50's library functions like get_string, get_int for user input.
• Variables in C have types: int, char, string, etc.
• Example: Reading user input and printing personalized messages.
• Format specifiers in printf: %s for strings, %i for integers.

Conditionals

• If-Else Statements: Similar to Scratch’s condition blocks.
• Syntax: if (condition) {...} else if (condition) {...} else {...}
• Example: Comparing two numbers and printing results.
• Importance of logical operators: ==, !=, >, <, <=, >=.

Loops

• While Loops:
  • Syntax: while (condition) {...}
  • Example: Counting down or up for repeated tasks.
• For Loops:
  • Syntax: for (initialization; condition; increment) {...}
  • Example: Printing patterns or repeated actions.
• Do-While Loops: Ensures code runs at least once.
• Example: Implementing a get_positive_int function.

Functions

• Defining custom functions:
  • Syntax: return_type function_name(parameters) {...}
  • Example: Creating a meow function to print sound effects.
• Prototypes: Necessary to declare functions above main().
• Importance in modularizing and reusing code.

Style and Design

• Code should be correct, well-designed, and well-styled.
• Use of tools like check50, style50, and design50 in CS50.

Practical Examples

• Mario: Printing pyramids using loops.
• Calculator: Implementing basic arithmetic with user input.
• Handling integer overflow and floating-point precision issues.

Common Issues and Solutions

• Integer Overflow: Limited by 32/64-bit storage.
• Floating-Point Precision: Limitations in representing decimals.
• Historical examples like the Boeing 787 and Pac-Man.
• Future concerns like the Year 2038 Problem.

Conclusion

• Emphasized understanding fundamental concepts over syntax.
• Previewed common challenges in computing with real-world examples.