C99, i.e. the C standard released in 1999 added a lot of features that make C code much more readable. Examples include:
Declarations anywhere in block
In C99, you can declare and initialize a variable anywhere: int x = 3;
Declare variables where they can be initialized; don't put all variables at the top of a function.
Declaration in for loop init-clause
In C99, you can write for (int i = 0; i < n; ++i).
This is ideal when i is only needed inside the loop.
Compound Literals and
Designated Initializers
In C99, you can assign a struct like:
p = (struct point) {.x = 3, .y = 5};_Bool and the
convenience alias bool
In C99, you can use _Bool instead of int for variables which can only be true or false.
#include <stdbool.h> for the bool convenience alias.