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by Richard Russell, January 2015
You may wish to convert a number to a string in assembly language (equivalent to the STR$ function in BASIC). This can easily be done by calling an internal routine within the interpreter. Here is how to do it (requires BBC BASIC for Windows version 6):
; eax = print format control (equivalent to @%) ; bx|ecx|edx = number to print (80-bit variant) ; edi = address of destination buffer push eax mov ebp,esp call @fn%(12) pop eax mov byte [edx+ecx],0
On completion a NUL-terminated string is stored in the supplied buffer.
To illustrate the use of this code here is a complete program which prints the value of PI using assembly language:
DIM Buffer% 255, P% 100, L% -1 [OPT 10 .ppi mov eax,&1414 ; G20 format mov bx,&4000 ; Value of PI ... mov ecx,&C90FDAA2 ; .. as an ... mov edx,&2168C235 ; .. 80-bit float mov edi,Buffer% ; Destination buffer
push eax mov ebp,esp call @fn%(12) pop eax mov byte [edx+ecx],0
mov esi,Buffer% .vout lodsb call "oswrch" or al,al jnz vout ret ]
CALL ppi PRINT