CS50 Lecture - Week 1 Notes

Overview

• The focus for this week is on learning C, a traditional programming language.
• Reminder: Concepts from last week (functions, loops, conditionals) are essential for this week.
• Today's goals: Solve problems using C and understand limitations of programming.

Introduction to C

• First Program: "Hello, World!"
• The transition from Scratch to C includes:
  • Functions: printf in C vs say in Scratch
  • Source code: What humans write vs Machine code: What computers understand (binary)

Development Environment

• Using CS50.dev for coding.
• VS Code interface:
  • Code writing area
  • Terminal window for commands
  • File Explorer for managing files

Writing Code in C

Basic Commands

• Creating Files: code filename.c
• Compiling Code: make filename
• Running Programs: ./filename

Example: "Hello, World!"

• Basic C structure:

  #include <stdio.h>
  int main(void) {
      printf("Hello, World!\n");
      return 0;
  }
  

Functions and Variables

• Functions are blocks of code that perform tasks.
• Variables store data values.
• Example of a function that prints multiple "meow" outputs.

Parameterized Functions

• Create functions with parameters:

  void meow(int times) {
      for (int i = 0; i < times; i++) {
          printf("meow\n");
      }
  }
  

Control Structures

Conditional Statements

• if, else if, and else to control flow based on conditions.

Loops

• While Loop: Executes code as long as a condition is true.
• For Loop: More succinct for iterating through a range of values.

User Input and Error Handling

• Use get_string, get_int, etc. from CS50 library for user input.
• Implement loops for validation of inputs (e.g., ensuring positive integers).

Memory Limitations

Integer Overflow

• Integer types can overflow when limits are exceeded (e.g., counting past 2^31 - 1).
• Example of how programming errors can lead to bugs in software (e.g., Pac-Man, Donkey Kong).

Floating Point Precision

• Floating point numbers can have imprecision due to limited representation in memory.
• Casting integers to floats for accurate calculations.

Final Notes

• Use comments to document code and improve readability.
• Practice working with commands in the terminal to manage files and run programs.
• Be aware of potential bugs and correct design in programming.

Conclusion

• This lecture set the foundation for programming in C, focusing on syntax, functions, control structures, and common pitfalls.
• Upcoming problem set 1 will allow students to apply these concepts.