Week 1: Introduction to C Programming

Overview

• Instructor: David Malan
• Topic: Introduction to C, building on basics from Scratch.

Key Concepts

Transition from Scratch to C

• Last week: Scratch - visual programming (functions, loops, conditionals)
• This week: C programming language - traditional syntax
• Purpose: Learn problem-solving tools for programming.

Importance of C

• Focuses on problem-solving with functions, variables, conditionals, loops, etc.
• Highlights limitations of computers in terms of solving problems and representing information.

Source Code and Machine Code

• Source Code: Code written by humans (high-level language)
• Machine Code: Binary code that computers understand (low-level language)
• Conversion by Compilers: Translates source code to machine code.

Programming Environment

• Using VS Code in the cloud (https://cs50.dev)
• Tabbed interface with text editor, terminal, and file explorer.
• Command-line Interface (CLI): Execute commands using the keyboard (e.g., compiling, running programs).
• Graphical-user Interface (GUI): Menus, icons, and interactions through mouse clicks.

Writing Simple C Programs

Hello, World in C

• Translate Scratch’s “Say” block to C:

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

• Importance of #include <stdio.h>, int main(void), printf, and \n.

Variables in C

• Declaration and initialization: int counter = 3;
• Modifying Variables:
  • counter = counter + 1;
  • counter += 1;
  • counter++;

Conditionals in C

• Example of an if statement:

  if (x < y) {
      printf("x is less than y\n");
  } else if (x > y) {
      printf("x is greater than y\n");
  } else {
      printf("x is equal to y\n");
  }
  

• Comparison of Scratch and C syntax

Loops in C

• While Loop: Repeat until a condition is false

  int counter = 3;
  while (counter > 0) {
      printf("meow\n");
      counter--;
  }
  

• For Loop: More compact syntax

  for (int i = 0; i < 3; i++) {
      printf("meow\n");
  }
  

• Infinite loop example using while (true)

User Defined Functions in C

• Creating custom functions:

  void meow(int n) {
      for (int i = 0; i < n; i++) {
          printf("meow\n");
      }
  }
  
  int main(void) {
      meow(3);
  }
  

• Function Prototypes: Declaring functions before use.

Common Functions in C

• CS50 Library: Simplifies getting user input (#include <cs50.h>)
  • Example functions: get_string(), get_int(), get_float(), get_char()

CLI Overview

• Common Commands: ls, cd, mkdir, mv, rm, cp
• File Management: Navigating directories, creating/removing directories/files, renaming and copying files.

Programming Challenges and Limits

Integer Overflow

• Definition: Exceeding the maximum value for an integer type causes it to wrap around.
• Example: Counting beyond the capacity of 32-bit integers (~4 billion).

Floating Point Imprecision

• Definition: Limited precision in representing real numbers due to fixed number of bits.
• Example: 1/3 not accurately represented beyond a certain number of decimal places.

Real-World Implications

• Historical bugs: Y2K bug, Boeing 787 software bug.

Summary

• Emphasized foundational programming concepts in C.
• Introduction to limitations of computing (integer overflow, floating point imprecision).
• Prepared for future discussions and problem sets by covering core syntax and logic in C.