unexpected things

• names of variables etc should (must?) be all lowercase; underscores are standard
• string is not a native data type in C—but the cs50 library provides it
• you need libraries to do like frickin ANYTHING geez,,,, you see stdio.h at the top of like every c program ever because it’s a library that needs to be included even just to print!
• strings must use double quotes and chars must use single quotes
• unlike some newer languages, you do need to declare things before you can use them (as in, above, on an earlier line)
• using a loop to check whether a user gave acceptable input

basics of C

• variables have to be initialized with a type

  • e.g. int n = get_int()

  • but you only have to do that once! you don’t need to write the type before the name anymore when you’re using it in subsequent lines

  • btw you can initialize them without an assignment too! int n; is a full, valid assignment.

    • but what does it initialize to when you declare without assigning?
      • well, int apparently defaults to 0, as revealed in the VS Code debugger during lecture 2

  • and you’re allowed to declare more than one per line, like int x, y; — note that you only need to say the type once, in that case.

    • are you allowed to declare variables of different types on the same line? obv it would be bad style but like, does it work?
• functions need types declared too! prefix the name with what type the function returns, and then inside the parentheses, prefix any args with what type they are
  • e.g. void meow(int n)
  • if it returns nothing, or if it takes no args, use void in place of the data type
  • so int main(void) means that main returns an int (?? somehow) and takes no args
• the compiler is basically translating your code from c into machine code (aka 1s and 0s)
• the compiler reads your code from top to bottom and will get confused if you try to use a function that isn’t defined until further down the page
  • BUT you don’t need to put the whole definition at the top! in fact it’s preferred to keep main up there as the first function defined, so that people can more easily see what your program does at a high level. you can leave the full definition lower down if you just add a one line declaration (called a prototype) at the top too.
  • prototype looks like: void meow(int n); and then you’ll still repeat that exact line (without the semicolon) when actually defining the function further down
• a side effect is the term for any other stuff a function does aside from the value it returns. e.g., printing to the screen is a side effect.

data types

• non-standard data types that come from cs50.h
• get_int get_string etc are special functions provided by the cs50 library, not standard parts of c
• qualifiers - extra keywords to modify a variable