TASKING VX-toolset for 8051 User Guide

TASKING VX-toolset for 8051 User Guide__rom char hello[] = "Hello\n"; /* initialized array in ROM only */__rom char *world = "world\n"; /* initialized pointerto string in ROM */Example with #pragma romstring:#pragma romstring__rom char hello[] = "Hello\n"; /* initialized array in ROM only */__rom char *world = "world\n"; /* initialized pointerto string in ROM */#pragma ramstringStrings in library routinesLibrary routines containing pointer arguments always expect the target memory of these pointers to bethe default RAM of the memory model used to make this library. For example:int printf( const char *format, ... );In the large memory model, this means printf() expects the address of the format string (the firstargument) to have memory type __xdata. Therefore, the C startup code of the large memory modelcopies all strings from ROM to XDATA. So, the statement:printf( "Hello world\n" );is executed correctly, because the 8051 compiler passes the address of the allocated XDATA area (filledat C startup time) to printf().With the --romstrings option specified, the string is put in ROM only and the standard printf/scanf likelibrary routines will fail.You will need to create your own __rom qualified versions. All library sources aredelivered. For example, you can use the source of printf() (in module printf.c) to create a__rom_printf(). The prototype could be:int __rom_printf( __rom char *format, ... );Modifying string literalsThe 8051 accepts that string literals are modifiable when strings are in both ROM and RAM. You can dothis with pointers, or even with a construct like:"st ing"[2] = 'r';Of course, when you use the --romstrings option this statement is not allowed.1.9. Switch StatementThe TASKING C compiler supports three ways of code generation for a switch statement: a jump chain(linear switch), a jump table or a binary search table.30