notes:beej’s guide to C

2024/08/27
- i’m bored, so instead of using social media, will try and read a page or two and write down some notes.
- why C
  - i want to eventually build an emulator with C and sokol
  - prepare myself to eventually write something playing for playb.it
  - learn about manual memory management, os api, low level stuff etc
  - read cool people code
- Hello, World!
  - there’s 2 stages to compile a C program: preprocess and compile
    - preprocess took everything inside #define, #include and put in your source code
    - then compile came in and spit out machine code for CPU to understand
  - main() then exit
  - compile with
    - ```
    gcc -o hello hello.c	
    gcc -o multi a.c b.c c.c 
```
- mac usually alias gcc with clang already (xcode dev thingy for git, etc)
- C Versions
  - big ones: C89, C99, C11, C2x
    - C89, ANSI C, C90: ANSI C standard
    - C99: add // comment, most popular (most likely most portable)
    - C11: support unicode and multithread, modern C
    - C2x: most updated
  - what to choose: just compile with gcc or clang
    - the book use C2x tho

2024/08/28
- Variables and Statements
  - variable is human readable name for data in a memory
  - memory is a big array of bytes
    - if something bigger than a bytes, then store with multiple bytes
    - a bytes = 8bits = 8 zeroes or ones
    - since memory is an array, then each bytes of memory can be refer with index. this index is called address, location or pointer
    - pointer is just an variable that hold address to a variable that lie on memory
  - variable types
    - string is char*
    - there’s actually no bool, only 0 and not 0
  - uninitialized variable have indeterminate value
    - must be initialized with value or else it must be nonsense number
  - pre(++i), post(i++) increment decrement
    - 5 + i++: 5 + i then i + 1
    - 5 + ++i: i + 1 then 5 + i
  - comma , operator
    - evaluate left to right, return right most
    - x = (1,2,3) => x = 3
  - sizeof operator
    - tell the size (in bytes) of variable or a type
      - sizeof a
      - sizeof(int)
    - depend on the system, except for char which always 1 bytes
    - sizeof return a size_t type
      - think size_t as value represents a count
    - is a compile time operation

2024/09/12
- Functions
  - anatomy return_type fn_name(args) {body}
    - fn_name(void) indicate function accept no arguments
  - all arguments is a copy, not a reference unless specify
    - But no fancy-schmancy name will distract you from the fact that EVERYTHING you pass to a function WITHOUT EXCEPTION is copied into its corresponding parameter, and the function operates on that local copy, NO MATTER WHAT. Remember that, even when we’re talking about this so-called passing by reference.
  - we can call function before defining it by using function prototype
    - omit the body and put it somewhere before calling the function
    - return _type fn(args) is a prototype
  - should always use fn(void) to indicate function take no argument
    - unless you really know what you doing, which i’m not.