C (Programming Language)

What is it?

C is just another programming language, like Python or Java. It’s different to them in a few ways though.

Key Distinctions:

• Not object orientated (there’s no classes, just collections of functions).
• Not interpreted (compiled into executable machine code).
• Run time errors (like Array Out-Of-Bounds Exception) are not caught by compiler. They’ll get caught in the program and crash the application lol.
  • This also can lead to security vulnerabilities.
• There’s only data structures (structs), with some statically stored and others dynamically (with malloc).
  • 
• There’s no boolean. 0 is False, anything else is True.

Pointers, Simplified:

I’ve rewritten this bit a lot, pointers are a tricky topic man. What are they? Pointers are just other variables that just happen to be the memory address of something else. Why? We use this to pass variables around without changing their addresses.

Example C code:

int x = 4; // This simply sets a variable x to the value 4. English: "Integer x is set to 4"
int* pX = &x; // English: "pX is a pointer to an integer, and it's set to the address of (&) variable x."
int y = *pX; // English: "y is a variable set to the value pointed to by pX"

The * operator can be used in two contexts:

1. For declaring a variable as a pointer that points to a specific data type
2. For dereferencing: If something is a pointer, adding a * gets you the value pointed to by that pointer. Otherwise, it’s just the address there.

Arrays in C:

• They’re fixed at the size declared at Initialisation.
• No knowledge of their length. (I.E. no checking if their indexing in bounds)
• Pointers are often used to carry arrays through functions.
• Index is 0 based.

Example Arrays:

int m[] = {5, 8, 10}; // size fixed to 3
int n[2][10]; // two-dimensional array
			  //  with 2 rows and 10 cols
point p[4];   // array of 4 structs

Strings in C:

• Strings are just arrays of chars.
• An extra bit is taken up as Strings end with \0.
  • $\therefore$ char s1[] = “string, too"; // length=12
• Assigning strings uses strcpy(s, "string!").

Warning!

When comparing strings using ==, you’re comparing if their addresses are the same. You likely want to instead compare if their values are the same.