This is the foundations page for the parent topic. Before we can read a monster like const int* const p, we must earn every symbol in it, from absolute zero. We go slowly. Nothing is assumed.
Before const can mean anything, we need to see what it modifies.
Look at the figure: the grey rectangle is the box, the word age floating above is the name, and the 10 inside is the value. Two separate things live here — the name and the value it currently holds. Keep that split in your head; const is a promise about one of these two things, and half of all confusion comes from not knowing which.
In the figure, an ordinary variable has a two-way arrow (read ↔ write). Adding const snaps a valve shut: the write arrow is crossed out in chalk-pink, only the read arrow (chalk-blue) survives. That is literally allconst does — it deletes the write direction.
We need types now because const is written fused onto a type: const int, const char. The const and the int together describe one box: "a whole-number box that is read-only." Where you place const relative to the type is exactly what we decode in Section 6. See constexpr and compile-time evaluation for the stricter cousin of const that must be known while the program is still being compiled.
To understand pointers (Section 5) we first need the idea of a memory address.
In the figure, boxes are drawn as houses on a street; the number under each house is its address. &age hands you the street number of the age house, not the person living there. Prerequisite reading: Pointers and References in C++.
This symbol confuses beginners because it wears two hats. We separate them here so Section 6 is clean.
Read the figure left to right: box p holds the number 1000 (an address). The chalk-blue arrow labelled *p walks from p to house 1000 and reads the 10 living there. So a pointer is a box holding a house-number, and * is the act of walking to that house.
Now every symbol is earned, we can decode the parent's table. The rule:
Walk each case slowly, right-to-left:
Map this back to the two-box picture (Section 5): const before * freezes the far box (pointee); const after * freezes the near box (the pointer). This exact skill powers Function parameters — pass by value vs const reference, where a const& parameter says "I read your data, I won't wreck it."
Each foundation feeds the next: boxes and assignment let us define the const valve; addresses let us define pointers; pointers plus the valve give the right-to-left reading; classes plus the valve give const methods. Together they become the full topic.
