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Hello world/Text: Difference between revisions
→{{header|ARM Assembly}}
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=={{header|ARM Assembly}}==
Developed on an Acorn A5000 with RISC OS 3.10 (30 Apr 1992)
Using the assembler contained in ARM BBC BASIC V version 1.05 (c) Acorn 1989
In the BBC BASIC part of the program I have included:
OS_WriteC = &00
OS_WriteO = &02
OS_NewLine = &03
this is so I can write SWI OS_WriteC etc instead of SWI &0 to make the assembler more legible
(a) method1 - output the text character by character until the terminating null (0) is seen
.method1_vn00
ADR R8 , method1_string \ the ARM does not have an ADR instruction
\ the assembler will work out how far the data item
\ is from here (in this case a +ve relative offset)
\ and so will produce an ADD R8 , PC, offset to method1_string
\ a magic trick by the ARM assembler
.method1_loop
LDRB R0 , [R8], #1 \ load the byte found at address in R8 into R0
\ then post increment the address in R8 in preparation
\ for the next byte (the #1 is my choice for the increment)
CMP R0 , #0 \ has the terminating null (0) been reached
SWINE OS_WriteC \ when not the null output the character in R0
\ (every opportunity to have a SWINE in your program should be taken)
BNE method1_loop \ go around the loop for the next character if not reached the null
SWI OS_NewLine \ up to you if you want a newline
MOVS PC , R14 \ return
\ when I call an operating system function it no longer operates
\ in 'user mode' and it has its own R14, and anyway the operating system
\ is too polite to write rubbish into this return address
.method1_string
EQUS "Hello world!" \ the string to be output
EQUB &00 \ a terminating null (0)
ALIGN \ tell the assembler to ensure that the next item is on a word boundary
(b) method2 - get the supplied operating system to do the work
.method2_vn00
ADR R0 , method2_string \ the ARM does not have an ADR instruction
\ the assembler will work out how far the data item
\ is from here (in this case a +ve relative offset)
\ and so will produce an ADD R0 , PC, offset to method2_string
\ a magic trick by the ARM assembler
SWI OS_WriteO \ R0 = pointer to null-terminated string to write
SWI OS_NewLine \ up to you if you want a newline
MOVS PC , R14 \ return
.method2_string
EQUS "hELLO WORLD!" \ the string to be output
EQUB &00 \ a terminating null (0)
ALIGN \ tell the assembler to ensure that the next item is on a word boundary
=={{header|ArnoldC}}==
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