What is an unused memory address?
Reading this HTML page on Commodore 64 memory allocations because I am interested in old computer hardware, I stumbled across a cell in the table that claims that the memory address is unused. What exactly does this entail? Does this mean that if you wanted to put something in that address you can put whatever you want? Confused, and would appreciate all answers. Thanks.
Memory maps should usually specify which programs use this memory. If they say "unused", this means that these specified programs do not use this address. Here you can see it better: https://www.c64-wiki.com/wiki/Zeropage:
Those zeropage addresses are useful and important in programming the C64 - so useful that the internal KERNAL and BASIC system ROMs make use of most of them, leaving only a handful that are completely "safe" for machine language programmers to use for their own purposes, without risking a system crash.
So, the memory map is only valid for KERNAL and BASIC.
Other programs - including yours - may access the unused addresses without risk. If other programs are loaded, you have to find out, which adressses are accesed by them. You may also access other addresses - even if they are used by other programs - if you know exactly what happens then...
- Can java disassembled code run without OS?
- Does little endian impact arrays?
- How is this function's assembly implementing the conditional?
- Practical uses for rotate carry left/right
- Horizontal XOR in AVX
- Effectively calculate horizontal pair avgs in a stream of int16's
- assembly 8086 space invaders project, int 10h doesnt work
- Comparing Unsigned integers using AVX2 Intrinsics
- Difference between "mov eax, [num]" and "mov eax, num"
- MIPS Program that shows the lowest of 3 user-inputted integers, doesn't register negative numbers
- Can AVX-512 be used to calculate the multiplication of two 256-bit Integers on a 64 bit computer in C++? Whether using Assembly Language or not
- Microarchitectural zeroing of a register via the register renamer: performance versus a mov?
- If-Else in assembly doesn't seem to work or I'm doing smth wrong
- NASM : _malloc allocating too much memory
- How to detect 16550 UART chip in MS-DOS x86 Assembly Language?
- Encoding "MOV EAX, moffs32" on x86-64
- otool error : is not an object file
- How to install NASM in windows 10?
- Loading and running a raw binary file with 32-bit code in QEMU
- Instructions for RISC-V(.word)
- Why there is '\' before the parameters in the arm assembly macro?
- How to display "The reversed string is:" and the reversed string on the same line in assembly language?
- Usage of recursion with array in MIPS
- Run Sparc binaries without Sparc hardware
- How to change a single bit of an address at assemble time?
- Zero-cost integer upcast via inline assembly
- GCC output Arm64 assembly instructions
- What does the null character do in `db` command?
- Why is my stack filled with 0xc2 instructions when I passed the 0x90 instruction?
- Statically loaded C to aarch64 Assembly, for learning purposes