1. Universal Definitions for the 16-bit Virtual Gameboy (GBVM) Library¶

File: univ_defs.h
Author: Soham Metha
Date: January 2025

The univ_defs.h file provides core definitions essential for the functioning of the GBVM library. It ensures consistency and reusability of standard types and constants across the library, which simulates a 16-bit virtual machine.

1.1. Table of Contents¶

1. Universal Definitions for the 16-bit Virtual Gameboy (GBVM) Library

1.2. Included Libraries¶

The following standard C libraries are included in univ_defs.h:

assert.h
ctype.h
errno.h
stdbool.h
stdint.h
stdio.h
stdlib.h
string.h

1.3. Constants¶

This file defines several constants used for configuring the GBVM's operational limits:

Constant Name	Value	Description
`EXECUTION_LIMIT`	`1024`	The maximum number of instructions that can be executed in a single session.
`PROGRAM_CAPACITY`	`1024`	The maximum size of the program memory.
`STACK_CAPACITY`	`1024`	The maximum size of the stack memory.
`MAX_WORD`	`32767`	The maximum value that can be stored in a `Word` type.

1.3.1. Example Usage¶

if (instructionCount > EXECUTION_LIMIT) {
    printf("Error: Execution limit exceeded.\n");
    exit(1);
}

1.4. Type Definitions¶

The file introduces custom type definitions for the GBVM's memory and processing needs:

Type Name	Base Type	Description
`Byte`	`char`	Represents a single byte.
`Word`	`short int`	Represents a 16-bit signed word.
`Double_Word`	`int`	Represents a 32-bit signed double word.
`Quad_Word`	`long long int`	Represents a 64-bit signed quad word.

1.5. Notes¶

The constants and types are designed to align with the 16-bit architecture of the virtual machine.
All custom types (Byte, Word, etc.) rely on their corresponding standard C types to ensure portability and clarity.
Always include univ_defs.h in files that require these constants or types.